Table of Content

31 January 2015, Volume 48 Issue 3

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Dissection of QTLs for Plant Height and Panicle Length Traits in Rice Under Different Environment

YAO Xiao-yun, LI Qing, LIU Jin, JIANG Shu-kun, YANG Sheng-long, WANG Jia-yu, XU Zheng-jin

Scientia Agricultura Sinica. 2015, 48(3):  407-414.  doi:10.3864/j.issn.0578-1752.2015.03.01

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【Objective】Panicle length and plant height are two important factors affecting rice production. Breeding varieties with large panicle and the ideal plant architecture traits are significant for increasing the grain yield of rice. To explore the genetic basis of plant height and panicle length in rice, quantitative genetic analysis was conducted in three different environments. In this study, stable expressed QTLs for plant height and panicle length were identified. The results of this study help us to understand the genetic basis of plant height and panicle length, and provide us with useful information for marker-assisted improvement of the plant type in rice.【Method】The recombinant inbred lines (RILs) derived from the cross between Shennong 265 (japonica) and Lijiangxintuanheigu (japonica) consisting of 126 lines were used to identify QTLs for plant height and panicle length in three different environments (Shenyang, 2011; Hainan, 2012; Shenyang, 2013). Nine QTLs were mapped by QTL IciMapping v3.0 software, using ICIM method for plant height and panicle length. In addition, based on the QTL results and the published literature and rice database data, the major QTLs in 3 environments were analyzed. These results were further confirmed the reliability of the QTL. Finally, in order to narrow the interval of the major QTLs, the QTL-BSA(Bulked Segregant Analysis of Major QTL) was used fine mapping.【Result】Analysis of variance test showed that a significant difference was detected between the parents under three different conditions. A normal distribution of phenotypic values for panicle length and plant height were observed, which indicated that panicle length and plant height were controlled by multiple genes. A total of nine QTLs for the plant height and panicle length were mapped. Five QTLs affecting plant height were detected on the chromosomes 6, 7, 9 and 12, with the LOD values ranged from 2.67 to 19.39, the additive effect from -17.68 to 2.90, and the range of individually explaining phenotypic variation was from 4.25% to 37.35%. A total of four QTLs for the panicle length were mapped on the chromosomes 6, 7 and 9, with the LOD values ranged from 3.57 to 23.18, the additive effect from -3.22 to 1.42, and the range of individually explaining phenotypic variation was from 11.30% to 61.62%. Of these, five were identified in more than one environments, four were significant in two or three environments, indicating that these QTLs are stable across years or environments. Among them, qPL9a and qPH9 were detected on the same region of chromosome 9 in three environments. qPH7 and qPL7b were mapped on the same interval of chromosome 7 in two or three environments, respectively. These QTLs’ alleles from LTH parent increased plant height and panicle length in this population. In addition, the analysis of major QTL-BSA mapping narrowed the qPHL9 (qPH9 and qPL9a)to a 522.46 kb region flanked by simple sequence repeat marker RM1189 and RM24457. qPHL7 (qPH7 and qPL7b) was mapped to a 856.49 kb interval flanked by simple sequence repeat marker RM478 and RM429 on chromosome 7. 【Conclusion】In this study, the recombinant inbred lines (RILs) derived from the cross between Shennong 265 (japonica) and Lijiangxintuanheigu (japonica) were used for mapping QTLs of plant height and panicle length. Five QTLs affecting plant height and four QTLs affecting panicle length were identified. Pleiotropic QTL region on the chromosome 9 could be detected in three environments. A novel plant height and panicle length pleiotropic QTL-qPHL7 was located on chromosome 7 in two environments.

Evolution of Genetic Distance Between Parental Lines of Chinese Sorghum Hybrids from1970s-2000s Based on SSR Analysis

WANG Rui, WANG Jin-sheng, ZHANG Fu-yao, CHENG Qing-jun, TIAN Cheng-hua, LING Liang

Scientia Agricultura Sinica. 2015, 48(3):  415-425.  doi:10.3864/j.issn.0578-1752.2015.03.02

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【Objective】To explore the genetic differences of Chinese sorghum varieties and evolution of the superior groups since heterosis utilization, SSR markers were used to identify the genetic distance of sorghum parental lines and F₁. Genetic background of Chinese sorghum main varieties in different periods were analyzed, and systematically understand of the genetic relationship, genetic diversity and genetic distance of sorghum hybrids and their parental lines can reduce the blindness of parental lines selection, effectively improve the predictability of cross breeding.【Method】SSR genetic distance of the representative hybrids and their parental lines grown in late-maturing area since 1970s were analyzed. Analysis of the superior groups of sorghum hybrids, research of the breeding progress and the evolution characteristics since heterosis utilization of sorghum were conducted at molecular level. 【Result】 A total 55 hybrids and their parental lines were evaluated by 109 pairs of SSR markers. The results revealed that 47 pairs of SSR markers were highly polymorphic. 373 varied alleles were amplified with an average of 7.5 alleles per marker, the ranges were 2 to 14. The ranges of PIC in 55 cultivars were 0.0351-0.8836, with an average of 0.6085. The genetic distance was averaged at 0.6011 with a range from 0.0889 to 0.9500. The sorghum materials were classified into 4 groups based on the SSR experiments. The clustering results were similar to those based on geographical origins and genetic backgrounds. The results showed that the average genetic distance between the two parental lines of hybrids from different eras showed a upward trend in 1970-1980, then a slight decline. According to the analysis of genetic distance between the two parental lines of hybrids from different heterosis models, Durra sterile lines×Kaoliang or trend Kaoliang restorer lines and Kafir-caudatum sterile lines×Kaoliang or trend kaoliang restorer lines have a far genetic distance, high yield, therefore, the heterosis model of Chinese sorghum hybrids should be Durra×kaoliang or trend kaoliang, Kafir-caudatum×kaoliang or trend kaoliang. 【Conclusion】In this study, it was found that the genetic distance between parental lines has a close relationship with heterosis level in sorghum, therefore, genetic distance should be fully considered in the matching of sorghum parental lines.

Interspecific Hybridization Among Vigna Species

LIU Chang-you, FAN Bao-jie, CAO Zhi-min, SU Qiu-zhu, WANG Yan, ZHANG Zhi-xiao, CHENG Xu-zhen, TIAN Jing

Scientia Agricultura Sinica. 2015, 48(3):  426-435.  doi:10.3864/j.issn.0578-1752.2015.03.03

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【Objective】The aim of this study was to analyze the crossability of different Vigna species, which will facilitate the distant hybridization breeding of Vigna. 【Method】 Interspecific crossabilities were investigated among 5 cultivar species of Vigna, V. radiata (mungbean), V. mungo (black gram), V. umbellata (rice bean), V. anguluris (adzuki bean), V. unguiculata (cowpea), and 3 wild relative species of adzuki bean, V. minima, V. nakashiame and V. riukiuensis. Embryo rescue was conducted for 3 interspecific combinations, namely, V. radiata×V. angularis, V. angularis×V. umbellata and V. umbellata×V. angularis, respectively. The pod setting ratio of hybrid and performance of F₁ plant were investigated to analyze the crossabilities between food legumes of Vigna genus. 【Result】 The genetic relationship between different food legumes and the choice of female parent influenced the result of distant hybridization. Except for cowpea cross combinations, hybrid pods were set successfully in the other interspecific crosses. The growth of hybrid pods and seeds showed variations in different combinations. No genetic disorders before fertilization were found from the hybridizations of V. radiata×V. mungo, V. angularis×V. minima, V. angularis×V. nakashiame, and V. angularis×V. riukiuensis. The hybrid seeds of them germinated normally, and the hybrid plants were fertile, but the fruiting rates were lower. The pod setting ratio was significantly higher when V. radiata was selected as female parent in the interspecific crosses between V. radiata and V. umbellata. F₁ plants were obtained without embryo culture, but they showed complete hybrid sterility. No fertile seeds were obtained even backcross to V. radiata or V. umbellata. Hybrid plants were obtained from cultured embryos for the interspecific crosses of V. radiata ×V. angularis and V. umbellata ×V. angularis. The fertility of F₁ plants from these two combinations was opposite, sterile in the former and fertile in the latter. The hybrid pods shriveled or fell off, or embryo abortion occurred in all other interspecific crosses. 【Conclusion】Using mungbean as the female parent was of benefit to the development of the hybrid pods and seeds when crossed with blackgram, adzuki bean and rice bean, respectively. The embryo abortion occurred when crossed blackgram with adzuki bean and rice bean, respectively. Through the use of embryo culture, the fertile F₁ plants could be obtained when using rice bean as the female parent crossed with adzuki bean. The crossability of adzuki bean with its wild relative was better than that of rice bean. All the crosses were failure when using cowpea as one of the parents.

AGRICULTURE INFORMATION TECHNOLOGY

Crop Roots Configuration and Visualization: A Review

WEN Wei-liang, GUO Xin-yu, ZHAO Chun-jiang, WANG Chuan-yu, XIAO Bo-xiang

Scientia Agricultura Sinica. 2015, 48(3):  436-448.  doi:10.3864/j.issn.0578-1752.2015.03.04

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As an important organ of absorbing water and nutrients for crops, root system architecture (RSA) has become a bottleneck in-depth study of crop roots due to the observing obstacles of soil. Three dimensional and visualization are important methods for studying and recognizing the morphological and structural traits of plants. In the aspect of crop root phenotype, these methods have a significance for characterizing the growth appearance of roots and for the influence of water, nutrients and other substances in the soil on RSA. In this paper, from the three dimensional perspective, the research progresses in detecting methods, three dimensional reconstruction and visualization of RSA in recent years were reviewed. Destructive and in situ detection methods of RSA were introduced. Destructive detecting methods mainly include (i) direct mining, (ii) protective soil block mining and cleaning, (iii) root scanning and image analysis, etc. These destructive methods have great advantages in obtaining global or local topology and extracting the plane geometric parameters. Meanwhile, in situ method mainly include six classes: (i) installation of root observation windows in field, (ii) ground penetrating radar, (iii) cultivation in controllable environment, (iv) CCD camera imaging, (v) 3D digitizing and (vi) X-ray computed tomography (CT), etc. These in situ methods retained the distribution information of RSA in space. However, most of the in situ detecting methods are only available for young or grown in controllable environment roots. Because a great deal of the detected data of RSA exist in the form of two-dimensional image, studies on extraction and analysis of plane geometry RSA parameters from two dimensional images were introduced as well, including root identification and parameter extraction algorithms and manual extraction software. Analysis showed that, the crop root data acquisition still exist some problems, such as time-consuming and laborious, redundant limitations, low integrity, difficult to integrate of each other, etc. Therefore, detecting and analyzing morphological traits of roots will still be the focus of RSA research. On the basis of RSA detecting technology, 3D modeling and visualization methods of RSA were reviewed on the aspects of 3D static modeling and dynamic growth simulation. 3D static modeling of RSA includes two kinds of methods: 3D modeling based on simulating algorithms and 3D reconstruction based on in situ detecting. Combining the computer simulation algorithms and understanding of RSA, the 3D modeling methods using simulating algorithms construct virtual roots with high morphological similarity of the real one. In contrast, 3D reconstruction based on in situ detection, which mainly includes XCT and 3D digital methods, could reflect the actual morphological structure of the RSA. Finally, the paper prospected the research on 3D reconstruction of crop roots under the condition of data missing. It was considered that 3D measurement and analysis of root topology could be realized using current technical means, while the 3D reconstruction of spatial distribution of RSA was difficult, especially in the premise of in situ measurement of crop roots in field. In addition, current 3D root data mainly have the data missing and low integration problems, so it is necessary to introduce the statistical methods like small sample theory and data fusion method into the research of 3D reconstruction of crop root to achieve a better reconstruction strategy by using multiple RSA data effectively in the premise of data missing.

The Agricultural Price Information Acquisition Method Based on Speech Recognition

XU Jin-pu, ZHU Ye-ping

Scientia Agricultura Sinica. 2015, 48(3):  449-459.  doi:10.3864/j.issn.0578-1752.2015.03.05

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【Objective】In this research, speech recognition technology was applied to collect agricultural price information. The aim of the research is to recognize the continuous speech which is limited in vocabulary and uttered by independent Chinese mandarin speakers, and to propose a robust speech recognition method suitable for the environment where agricultural product prices are collected. On the basis of Hidden Markov Model (HMM), we train the acoustic models for this environment, so as to relieve the decrease of recognition rate caused by the mismatching between the test environment and the training environment, and to make further improvement of the recognition rate. 【Method】 In the stage of acquiring and processing data, we first built the transformation grammar according to certain rules to recognize the limited vocabulary, and this grammar will be used to guide the recording of both train data and test data. Then we select different environments to collect agricultural product prices by different speakers. On this basis, we built a speech corpus in which speech data are artificially segmented with accuracy. In the stage of training model, we choose the continuous mixed density Hidden Markov Model with left-to-rigt and non-jump structure, and extract 39 demension MFCC feature vector from training dataset to train the HMMs. Firstly, we select monophones as the recognition unit to train male HMMs, female HMMs, and male-female mixed HMMs. Taking it into consideration that the monophones are poor in stability and vulnerable to coarticulation, we select context-dependent triphone as the decoding unit to retrain above HMMs. Since the number of triphones models will increase significantly when the triphones are chosen as modeling unit, we use the decision tree clustering to solve the insufficiency of training samples. In the process of building a decision tree, we divide all the finals and initials into different sets by using the phonetic knowledge. For the identification of initials, we appeal to their pronunciation way and place, and for the finals, we resort to their constitution and head vowels. In this way we realize the design of binary value questions. On this basis, we increase Gaussian mixture components to make the model more accurately described. Besides, in order to solve the problem of convolution noise in the communication channel, we adopt the CMN and CVN methods to alleviate the mismatching problem between test environment and training environment. Finally, the male and female HMMs are obtained respectively by training. In the stage of test, for the different models employing different methods mentioned above, we do the test experiments with the same test dataset respectively and obtain the sentence recognition rate, word recognition rate, and accuracy of every different method. 【Result】 The results show that recognition performance of triphone models are superior to monophone models. Both male and female HMMs perform better than the male and female mixed acoustic models. Though decision tree clustering method cannot promote recognition rate significantly, it can reduce the quantity of triphone models evidently. Gaussian mixture components improve the recognition rate on the one hand, but they bring a certain amount of increase in calculation on the other. CMN and CVN methods can significantly improve the performance of identification system. Through the different locations and different speaker test, the methods we have used demonstrated varying degrees improvement in the recognition performance. The ultimate recognition rate was 95.04% for males, and 97.62% for females.【Conclusion】It is feasible to apply speech recognition technology to the collection of agricultural product price information. In this paper, we proposed a method to improve the recognition rate in agricultural product price information acquisition. The experiment results show that the models trained by these methods have a good recognition performance. Furthermore, the approach adopted by our research lays a foundation for the development of the application system in the future.

Platform Construction of Vegetable Safety Warning and Traceability Based on Modern Information Technology

DIAO Hai-ting, NIE Yi-min

Scientia Agricultura Sinica. 2015, 48(3):  460-468.  doi:10.3864/j.issn.0578-1752.2015.03.06

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【Objective】 A study was made for the purpose of warning and tracing the quality safety of vegetables from production to sale by modern information technology.【Method】In this study of vegetables from Shouguang City, the national production and demonstration base of vegetables, the authors mainly addressed the gathering of information on vegetable quality, safety supervision and traceability management in that city, by means of the WebGIS, the Internet of things, bar code identification, and database technology. In this research, the vegetable logistics data acquisition and storage were studied, and the platform construction of the system of vegetable safety warning and traceability was explored.【Result】The authors used the networking data acquisition technology, established a set of attribute database using SQLServer2008 database consisting of data of vegetable production, processing, transport and sale. A set of vegetables safe spatial data were produced by means of GIS, which includes the Shandong road map, Shouguang sampling map, and Shouguang soil nutrient map. On that basis, a set of effective vegetable safety warning and traceability platform was established. The platform consists of a variety of information technology, with consideration of the business needs of the vegetable safe production of Shouguang City. The whole platform is divided into four modules: data query, vegetable quality safety warning, vegetable quality safety traceability, and auxiliary tool. The platform is designed for the following: the vegetable information inputting and editing, vegetable information query, warning traceability, vegetable information stereoscopic display, the best path analysis, vegetable soil nutrient statistics, vegetable soil nutrient interpolation, etc. The real-time early warning system can transmit the information of coordination, temperature, humidity and time to the server with network real-time data acquisition. The platform can also monitor and forecast vegetables temperature, humidity, shelf life, to ensure the quality and safety of vegetables. As for the function of vegetable quality safety traceability, the authors trace the path of logistics and distribution on the map according to the vegetable bar codes and logistics coordinate. To fulfill the path analysis function, one can design the path for the optimum according to the transport of vegetables and destination. The function of vegetables spatial information display can be achieved by means of the vertical surface of stereoscopic display from the soil to the ground and the atmosphere, namely, the integration of three-dimensional space and different times. 【Conclusion】This study demonstrates the process from vegetable production to sale using the GIS technology. The system under discussion is of great help to improve vegetable quality and safety management. To some degree, the system has been proved effective for the government departments concerned for the sake of supervision of vegetable safety.

PLANT PROTECTION

Influence of Leptochloa chinensis on the Growth of Paddy Rice and Its Economic Threshold

WU Shang, ZHANG Ji-li, LI Bao-tong, TANG Li-mei

Scientia Agricultura Sinica. 2015, 48(3):  469-478.  doi:10.3864/j.issn.0578-1752.2015.03.07

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【Objective】 Red sprangletop (Leptochloa chinensis (L.) Nees.) is a troublesome weed seriously damaging rice growth and reducing rice yield in direct-seeding rice fields. The objective of this study is to investigate the effects of L. chinensis on rice growth in direct-seeding rice fields and its economic threshold, and provide a scientific basis for the formulation of control parameters on L. chinensis in direct-seeding rice fields and its control measures. 【Method】 A field experiment was carried out to study the effects of L. chinensis of different densities (0, 1, 3, 6, 9, 12, 15, 18 and 21 plant/m²) on the growth of middle, early and late rice of double seasons and their yields by the method of additive series experiment. The function relation between L. chinensis of different densities and forming factors of rice yields and their yield loss were investigated by the method of curve fits. Control economic thresholds on L. chinensis in different types of paddy fields were derived on the basis of the economic infestation level (EIL) formula. 【Result】 The plant height, tillers, effective spikes, filled grains per panicle, 1000-grain weight and grain yield of direct-seeding rice decreased gradually with the interference of L. chinensis as the weed density increased. Compared with the control, plant height of early, middle and late rice dropped by 11.73%, 4.80% and 7.82% at L. chinensis density of 21 plant/m², respectively, tillers dropped by 22.08%, 29.67% and 19.22%, respectively, effective spikes dropped by 12.00%, 25.57% and 21.43%, respectively, filled grains per panicle dropped by 13.28%, 15.07% and 14.82%, respectively, and 1000-grain weight dropped by 12.11%, 11.99% and 7.03%, respectively, which resulted in rice yield dropped by 39.22%, 44.36% and 37.80%, respectively. The quadratic regression model y=ax²+bx+c was relatively better for describing the relationship between L. chinensis density and plant height of early rice (y=-0.0037x²-0.1389x+57.2631, P＜0.001), middle rice (y=-0.0007x² -0.0816x+77.0617, P＜0.001) and late rice (y=-0.0006x²-0.2032x+78.0150, P＜0.001), tillers of early rice (y=0.0229x²-3.5944x+331.5809, P＜0.001), middle rice (y=-0.0529x²-5.3734x+464.9348, P＜0.001) and late rice (y=0.0302x² -3.7612x+399.7899, P＜0.001), and effective spikes of early rice (y=-0.0259x²-1.3288x+282.2607, P＜0.001), middle rice (y=0.0208x²-4.9362x+366.0443, P＜0.001) and late rice (y= 0.0412x²-3.6170x+326.3593, P＜0.001), while logarithmic regression model y=alnx+b was the best for filled grains per panicle of early rice (y=-2.8309lnx+87.8309, P＜0.001), quadratic regression model y=ax²+bx+c was the best for that of middle rice (y=0.0434x²-1.6046x+94.9940, P＜0.001) and late rice (y=0.0084x²-0.8042x+93.7427, P＜0.001). Meanwhile, the quadratic regression model y=ax²+bx+c was relatively better for describing the relationship between L. chinensis density and 1000-grain weight of early rice (y=0.0051x²-0.2633x+27.1196, P＜0.001), middle rice (y=-0.0003x²-0.1312x+25.7605, P＜0.001) and late rice (y=-0.0022x²-0.0335x+26.0215, P＜0.001), and grain yields of early rice (y=2.1426x²-144.7765x+6674.9628, P＜0.001), middle rice (y=5.3452x²- 298.2884x+8933.8063, P＜0.001) and late rice (y=1.4743x²-156.4516x+7906.4028, P＜0.001), while the power regression model y=ax^b was the best for yield loss of early rice (y=8.6313x^0.4757, P＜0.001), middle rice (y=2.5916x^0.9722, P＜0.001) and late rice (y=4.6306x^0.6864, P＜0.001). For yield levels of 7 500 kg•hm^-2 (early rice), 9 750 kg•hm^-2 (middle rice) and 8 625 kg•hm^-2 (late rice), the economic infestation levels for manual weeding were 12.73%, 8.80% and 10.07%, respectively, and the red sprangletop economic thresholds were 2.26, 3.52 and 3.56 plant/m², respectively. Also for yield levels of 7 500 kg•hm^-2 (early rice), 9 750 kg•hm^-2 (middle rice) and 8 625 kg•hm^-2 (late rice), the economic infestation levels for application of 10% cyhalofop-butyl EC or 30% oxaziclomefone SC were 2.26%-2.72%, 1.56%-1.88% and 1.77%-2.12%, respectively, and the L. chinensis economic thresholds were 0.06-0.09, 0.59-0.72 and 0.25-0.32 plant/m², respectively. 【Conclusion】The inhibitory effects of L. chinensis on rice were positively correlated with its density, which there were differences among early, middle and late rice. Also the economic thresholds of chemical control on L. chinensis showed early rice＜late rice＜middle rice based on the analysis of control economic thresholds.

Epidemic Dynamics of Apple Marssonina Leaf Blotch over Whole Growth Season in the Central Area of Shandong Peninsula

DONG Xiang-li, GAO Yue-e, LI Bao-hua, YONG Dao-jing, WANG Cai-xia, LI Gui-fang, LI Bao-du

Scientia Agricultura Sinica. 2015, 48(3):  479-487.  doi:10.3864/j.issn.0578-1752.2015.03.08

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【Objective】 Marssonina leaf blotch is a main disease of apple leaf in China, which causes severe defoliation of apple tree in early growth season. The objective of this study is to understand the epidemics of Marssonina leaf blotch in whole apple growth season and provide data or information for prediction and management of the disease. 【Method】 From March to July during 2009 and 2010, apple leaves with Marssonina leaf blotch lesions were randomly picked every 15 days from ground of two apple orchards in Laiyang and Qingdao, Shandong Province. Fruiting bodies of the fungus were cut out from lesions on the upper side of sampled leaves and examined for asco-spores and pseudo-conidia under a microscope. Development dynamic of primary infection inoculum on overwintered diseased leaves was analyzed base on the percentage data of apothecium and pseudo-acervulus. From June to October during 2008, 2009 and 2010, incidences of diseased and defoliated leaf on the same shoots were surveyed every 15 days in orchards located in Laiyang and Qingdao. The incidence data were used to fit logistic models and model parameters were calculated to describe the epidemic dynamics of the disease. From September to November during 2010 and 2012, apple leaves with typical Marssonina leaf blotch lesions were sampled every 10 days. Acervula were cut out from the lesions and examined under a microscope for the small type spore and the conidia. Percentages of the small type spore relative to conidia were used for analyzing formation dynamics of the small type spores. 【Result】 Diplocarpon mali produced asco-spores and pseudo-conidia on overwintered disease leaves. Pseudo-conidia were produced from early March to the end of June with peak in middle of May. Pseudo-conidia were mainly dispersed with rain splashing water and mainly infected leaves on the bottom of the trees form the beginning of apple leaf growth. The infected leaves by pseudo-conidia often defoliated before the end of June and had little influence over other leaves on late onset. Asco-spores matured from middle of May to the end of June, discharged in rain and dispersed with airflow. Asco-spores chiefly infected leaves of main parts in apple tree and the infected leaves provided inoculum for the epidemic of the disease in late growing season. The primary infected leaves by D. mali on main part of apple trees began to show symptoms from early or middle of July. Diseased leaves accounted for approximately 2% of all the leaves at the beginning of disease development. In July, the primary infected leaves began to show symptoms and sporulation, and the infected new health leaves. The infected leaves showed symptom continuously in July and incidence of diseased leaves rose up to 5% at the end of the month. In August, most of the infected leaves in early season showed symptom, produced a large amount conidia and infected healthy leaves, resulted in rapid increase of disease leaves. The disease development reached its’ peak on late August and 12 days later the diseased leaves were defoliated. Dynamics of the disease epidemic and defoliation from June to September can be well described by two logistic models. From the beginning of September, the pathogen began to produce a small kind of spore, which was consider as sexual spore, and relative proportion of the small type spore on acervulus were increased in linear style with time elapse. In October, the pathogen gradually stopped to produce conidia, the only infection spores in growing season, on lesions and prepared for overwintering. 【Conclusion】 Epidemics of apple Marssonina leaf blotch in the central area of Shandong peninsula can be divided into four periods: From apple leaves growth to the end of June is the primary infection stage, and infection by asco-spores is mainly from late May to the end of June; July is the exponential growth stage of the disease; August and September are the logistics growth stage of the disease; October and November are period for the pathogen to prepare for overwintering. The asco-spores infection stage and exponential growth stage of the disease are key period to control the disease epidemics with fungicides.

SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT

Effects of Long-Term Fertilization on Organic Carbon and Nitrogen Accumulation and Activity in a Paddy Soil in Double Cropping Rice Area in Dongting Lake of China

LI Wen-jun, PENG Bao-fa, YANG Qi-yong

Scientia Agricultura Sinica. 2015, 48(3):  488-500.  doi:10.3864/j.issn.0578-1752.2015.03.09

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【Objective】Soil organic matter and its activity are essential indexes for assessing soil fertility, so the responses of total organic carbon (TOC) and nitrogen (TN) accumulation and its activity to various long-term fertilization in a double cropping rice soil were studied in Dongting Lake region, China, which can provide a scientific basis for improving fertilization management and soil fertility in paddy soils. 【Method】Based on a national experimental platform which was arranged in the Hanshou county, Hunan province, test samples in the surface (0-20 cm) and subsurface (20-40 cm) of a paddy soil after 26 years of fertilization treatments were collected and SOC, TN content and storage were measured, as well as soil microbial biomass carbon (MBC) and nitrogen (MBN), dissolved organic carbon (DOC) and nitrogen (DON) contents were also analyzed. The experiment included six treatments: (1) CK, unfertilized control; (2) CF, farmers’ practice of applying chemical fertilizer NPK; (3) NK, application of chemical fertilizer NK; (4) NPK, balanced application of chemical fertilizer NPK; (5) LOM, combined application of chemical fertilizer NPK and 30% organic fertilizer; (6) HOM, combined application of chemical fertilizer NPK and 60% organic fertilizer. 【Result】The content of TOC at 0-20 cm soil layer changed slightly when no fertilizer applied for 26 years and its value only increased by 0.64 g·kg^-1 throughout the period, suggesting that long-term cropping rice was beneficial to TOC sequestration. After long-term application of chemical or organic fertilizer, the content of TOC and TN in two soil layers increased significantly (P＜0.05), however, their storage significantly (P＜0.05) enhanced only by balancing NPK chemical fertilizer application or applying organic fertilizer. For all the treatments, the content of MBC, MBN, DOC and DON declined with the soil layer deepened, and its variation amplitudes at 0-40 cm layer were 64.54-708.76, 22.92-92.25, 39.06-63.24, and 10.76-31.87 mg?kg^-1, respectively. Compared to the CK treatment, the contents of soil MBC, MBN, DOC, and DON at 0-20 cm layer in fertilized treatments increased by 34.1%-81.8%, 56.1%-134.4%, 23.5%-42.0%, and 20.3%-83.2%, respectively, while at 20-40 cm layer they increased by -3.8%-38.1%, 32.5%-78.2%, 8.2%-37.5%, and 9.3%-56.8%, respectively. It also showed that the contents of each labile organic C and N fraction at the same soil layer in all the chemical fertilizer application treatments were much smaller than that in LOM and HOM treatments. However, the contents of all labile organic C and N fractions at 0-20 cm layer were insignificant (P＞0.05) among the CF, NK and NPK treatments. With the deepening of soil, the proportion of labile organic N fractions to TN and microbial quotient decreased, but the proportion of DOC to TOC increased. No matter which soil layer was concerned, the MBC/TOC, DOC/TOC, MBN/TN and DON/TN ratios in soil increased when fertilization was adopted, and the effect was significant (P＜0.05) when combined application of chemical fertilizer NPK and organic fertilizer and HOM treatment presented the best result. The soil MBC, MBN, DOC and DON contents in different treatments were significantly correlated to each other and presented a significant (P＜0.05) correlation with soil TOC, TN, bulk density and pH, but weakly (P＞0.05) correlated with C/N ratio and clay content. On the whole, the correlation coefficients obtained by MBC and MBN were higher than that of DOC and DON. Long-term fertilization significantly (P＜0.05) increased the early and late rice yields, the contents of all organic C and N labile fractions in two soil layers were positively correlated with annual rice yields, and with the deepening of soil, the correlation coefficients generally decreased (P＜0.05). 【Conclusion】 In the double cropping rice region of Dongting Lake, as to the same type of soil organic matter component, the content of labile N fraction in fertilized treatments presented a more obvious increasing effect than that of C fraction. Combined application of chemical fertilizer NPK and organic fertilizer, the activity of TOC and TN in two soil layers was significantly increased compared to the unfertilized control, which was the most effective practice for improving the accumulation of soil TOC and TN at 0-40 cm layers as well as the soil productivity. Soil MBC and MBN were more sensitive to predicting the change of soil quality after long-term different fertilizations.

Modeling the Future Changes of Soil Organic Carbon Under Different Management Practices in Upland Soils of Northeast China

LI Yue, GUO Li-ping, XIE Li-yong, HUANG Shu-qing, XU Yu-xiu, ZHAO Xun

Scientia Agricultura Sinica. 2015, 48(3):  501-513.  doi:10.3864/j.issn.0578-1752.2015.03.10

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【Objective】The effects of different agricultural management practices on soil organic carbon in Northeast China were studied in order to provide a scientific basis for sustainable development and low carbon agriculture aiming at high yield, high nutrient efficient and low pollution in Northeast area. 【Method】Different agricultural management practices can affect the future changes of soil organic carbon (SOC). This study calibrated the DAYCENT model by using observed crop yield and SOC standards, which based on the collected data of four long-term experiment sites in Northeast China (Harbin Heilongjiang, Gongzhuling Jilin, Dehui Jilin, Shenyang Liaoning). DAYCENT model parameters need to be adjusted, which include crop parameters, tillage parameters, fertilization parameters, harvest parameters, organic fertilizer parameters and so on, and then this study validated the model by using adjusted parameters after calibrating. The simulated and measured values were fitted well, which indicated that the DAYCENT model is applicable to simulation of crop yields and SOC of these four areas and can simulate the dynamic changes of SOC well. The calibrated and validated model was used to simulate the future changes of SOC under four different management practices (fertilizer application, organic manure augment, straw incorporation, and no-tillage) at the future climate change scenario (representative concentration pathway 4.5, RCP 4.5). 【Result】 The simulation results showed that SOC will be increased rapidly in a short period of time by using combined application of organic manure and chemical fertilizer (MNPK) at Harbin site. Although the increasing slope of SOC for lower rate of manure combined with chemical fertilizers and chemical fertilizer showed a consistency in a long period of time, but the absolute value of future SOC content will be higher for MNPK compared to NPK due to its higher initial SOC content. The SOC of no-tillage treatment showed lower than conventional tillage in a short period of time at Dehui site, but no-till seemed to be more effective in increasing SOC in a long period of time though with relatively slow increasing speed, which relatively increased SOC by 11.88% in future 40 years. Combined application of manure with chemical fertilizers and straw incorporation can improve SOC significantly at Gongzhuling site. Due to a slight decreasing trend at Shenyang site, SOC will be decreased by 2.83% in the next 42 years if fertilizers are applied only, so the authors suggested that combined application of organic manure and chemical fertilizers and other carbon addition practices must be adopted. 【Conclusion】 DAYCENT model can simulate the dynamic changes of crop yield and soil organic carbon effectively, which has a strong adaptation, while DAYCENT model can be used to simulate the dynamic changes of the SOC at sites in the future. The goal of sequestration carbon can be achieved by using combined rational rate of manure with chemical fertilizers, adopting no-tillage and straw incorporation technologies in Northeast China.

Effects of Different Plastic Film Mulching Methods on Soil Water and Temperature as well as Watermelon Yield in Loess Dryland

MA Zhong-ming, BAI Yu-long, XUE Liang, DU Shao-ping

Scientia Agricultura Sinica. 2015, 48(3):  514-522.  doi:10.3864/j.issn.0578-1752.2015.03.11

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【Objective】Watermelon is one of the main cash crops in the semi-arid regions of Loess Plateau and its planting area has been expanding steadily in recent years. However, due to insufficient precipitation and its uneven temporal and spatial distribution, watermelonoften suffers from water stress and waterlogging, resulting in yield reduction. The objectives of this study were to explore rainfall-collection and high-yield cultivation techniques in order to improve soil moisture-thermal conditions by plastic film mulching.【Method】The experiment was implemented in Taichang Township of Ning County, Gansu Province in 2011-2013 with the aim to identify the effects of different cultivation methods on soil water, soil temperature and yield. The trial was a random block design with 3 replications, and 5 treatments which included sowing on beds with full plastic film mulching (RM), furrow sowing on beds with full plastic film mulching (GM), sowing in furrows with full plastic film mulching (TG), furrow sowing on beds with half plastic film mulching (GH), sowing on beds with half plastic film mulching (RH). The bed width was 100 cm with furrow width 30 cm. For GM and GH treatments the width of furrow on top of bed was 20 cm and the depth was 10 cm. Soil moisture in 0-100 cm profile was measured by drying method. Soil temperature was checked by Stow Away Tidbit Temp Logger at the soil layers of 5 cm, 10 cm and 15 cm. The planting density in each treatment was 7 692 plants/hm².【Result】Soil moisture was affected by collected rainfall and stage of watermelon growth. Compared to RH, soil water contents of TG, GM and GH in 0-10 cm increased by 41.41%, 37.82 and 32.69% at seedling stage, TG, RM and GH in 0-40 cm increased by 13.91%, 10.61% and 6.75% at extension stage, GM and GH in 0-40 cm increased by 8.50% and 5.49% at fruiting stage and GM, GH, TG and RM in 0-40 cm increased by 10.51%, 10.33%, 4.98% and 3.66% at maturing stage, respectively. The sequence of soil water storage was as GH＞GM＞TG＞RM＞RH at fruiting stage. The daily variation of soil temperature changed as ‘S’ type negative sine curve, the amplitude decreased, the phase shifted backwards and the cycle extended with soil depth deepened. The sequence of average daily soil temperature was as RM＞RH＞GM＞TG＞GH. The time of maximum and minimum daily soil temperature was delayed 1 h as soil depth deepened every 5 cm. Soil temperature of the beds was higher than that of furrow and soil temperature of RM was the highest among all treatments. The sequence of soil temperature increase was as GM＞TG＞GH＞RH＞RM. The yield of GM in 2012-2013 was the highest and increased by 10.34% and the yield of GH in 2011-2013 increased by 7.66% compared to RH. The sequence of yield increase was as GM＞GH＞RM＞TG. The function of rainwater collection and yield increase of GM and GH were significantly improved.【Conclusion】The effects of rainfall collection, soil temperature increase and watermelon yield improvement were verified by 3-year study. GM and GH can collect more rainfall, increase soil temperature and promote yield. Application of the techniques can effectively improve the rainfall utilization and achieve stable and higher yields. It can also be used as a highly effective cultivation solution for watermelon production in dryland areas on the Loess Plateau.

HORTICULTURE

Pyramiding Disease Resistance Genes and Variety Improvement by Molecular Marker-Assisted Selection in Melon (Cucumis melon L.)

BI Yan-fei, XU Bing-hua, QIAN Chun-tao, GUO Jing, ZHANG Yong-bing, YI Hong-ping, CHEN Jin-feng

Scientia Agricultura Sinica. 2015, 48(3):  523-533.  doi:10.3864/j.issn.0578-1752.2015.03.12

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【Objective】Gummy stem blight (GSB) is caused by Didymella bryoniae and is a serious fungal disease of melon (Cucumis melon L.). The resistance of melon varieties carrying a single resistance gene is not enough to the disease because of the isolates variation of Didymella bryoniae. Therefore, this study aims to develop a molecular marker-assisted selection system and provide an important intermediate materials for melon disease-resistance breeding. 【Method】Firstly, the single resistant sources PI140471, PI157082, PI511890, PI482398 and PI420145 were used to obtain polymerization resistant sources (082-471, 082-890, 082-398, 145-471, 145-082, 145-890, 145-398 and 890-398). Secondly, three different gradient spores vaccination identification (5×10⁵ spores/mL, 5×10⁷ spores/mL and 5×10⁹ spores/mL) was employed to distinguish the resistance of F₁ plant of eight different polymerization resistant sources. The gene combinations of 145-471 and 145-398 with their resistance significantly improved were screened by inoculation identification results of spring and autumn. Single resistant sources PI140471, PI482398 and PI420145 were used as the donor parents with the gummy stem blight resistance genes Gsb-1 Gsb-4 and Gsb-6, respectively. Commercial melon cultivar Baipicui was used as the receipt parent to cross and backcross with the donor parents. Marker assisted selection (MAS) and gradient spores vaccination identification (5×10⁵ spores/mL, 5×10⁷ spores/mL and 5×10⁹ spores/mL) were used in each backcross and self-cross progeny. 【Result】The single resistant sources showed lower resistance than polymerization individuals and showed selective resistance to the different gummy stem blight spore concentrations (5×10⁵ spores/mL, 5×10⁷ spores/mL and 5×10⁹ spores/mL). The detection results of molecular markers showed that all the individuals of 145-471 (or 145-398) F₇ and BC₅F₄ generation had two resistance genesof Gsb-1 and Gsb-6 (or Gsb-4 and Gsb-6). The polymorphism of molecular markers was different among the parents. The PCR amplification of SSR marker CMCT505 could augment one specific fragments of 189 bp in single resistant source PI140471. The PCR amplification of SSR marker CMTA170a could augment one specific fragments of 121 bp in single resistant source PI482398. A 1 800 bp specific fragment was obtained with SCAR marker SGSB₁₈₀₀ in resistant source PI420145. The polymerization individual 145-471 could be amplified two fragments of 189 bp and 1 800 bp by SSR marker CMCT505 and SCAR marker SGSB₁₈₀₀. The polymerization individual 145-398 could be amplified two fragments of 121 bp and  1 800 bp by SSR marker CMTA170a and SCAR marker SGSB₁₈₀₀. At F₇ generation, the pyramiding lines with homozygosity at both gene loci were obtained. The polymerization individuals showed higher resistance than single resistant sources PI140471, PI482398 and PI420145. The individuals were resistant to melon gummy stem blight, which was accordant to the expected result of molecular detection. Improved Baipicui BC₅F₄ generation showed high resistance to melon gummy stem blight and had no significant differences in fruit weight, fruit shape index, fruit crispness, flesh texture, flesh thickness and soluble solids content compared with the Baipicui. A molecular marker-assisted selection system was developed and thus providing important intermediate materials for melon disease-resistance breeding. 【Conclusion】The results of disease resistance evaluation indicated that the molecular markers developed in the study were efficient in selecting three resistance genes by MAS. The molecular marker-assisted selection system developed in this study was efficient for pyramiding multiple resistant genes. The resistance improved materials of Baipicui would be used in breeding and further resistance gene pyramiding.

Growth Status, Root Morphology andPhysiologicalCharacteristics of Four Citrus Rootstocks Under Different Phosphorus Levels

FAN Wei-guo, LUO Yan

Scientia Agricultura Sinica. 2015, 48(3):  534-545.  doi:10.3864/j.issn.0578-1752.2015.03.13

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【Objective】Effects of different phosphorus (P) levels on the plants growth, roots morphology and related physiological characteristics of citrus rootstocks were studied for providing a scientific basis of high P efficiency citrus rootstocks excavation.【Method】The wild Citrus ichangensis Swingle, C. aurantium L., C. limonia Osbeck and cultivated species Poncirus trifoliata Raf. in Guizhou Karst mountain were used as materials, and the date including the growth and biomass, root morphological characteristics, activity of acid phosphatase (APase) and nitrate reductase (NR) of leaves and roots, and secretory acid phosphatase (SAPase) of roots and root absorption kinetics of P characteristics were researched through sand cultivation.【Result】The growth and development of C. ichangensis Swingle was less inhibited under 5 mg•L^-1 P level, followed by C. limonia Osbeck and C. aurantium L., restrained intensively to P. trifoliate Raf.. When P concentrations of nutrient solution was 25 mg•L^-1, the amount including the plant height, base diameter and fresh weight and dry weight of biomass, total root length, total surface area, total volume and total root tip reached the maximum for C. ichangensis Swingle and C. limonia Osbeck, followed by 5 mg•L^-1 P level, 45 mg•L^-1 P level was the minimum. With the P concentrations of nutrient solution increasing, the data including the plant height, base diameter and fresh weight and dry weight of biomass, total root length, total surface area, total volume, total root tip amount and root-shoot ratio of C. aurantium L. and P. trifoliata Raf. increased, however, the root-shoot ratio of C. ichangensis Swingle and C. limonia Osbeck decreased. Under low P conditions, C. ichangensis Swingle had the biggest lateral root roughness and the second lateral roots amount and root-shoot ratio, the NR activity in leaves was all in the order of C. ichangensis Swingle ＞C. limonia Osbeck ＞C. aurantium L. ＞P. trifoliata Raf., the NR activity in roots was all in the order of C. aurantium L. ＞C. limonia Osbeck ＞ C. ichangensis Swingle＞P. trifoliata Raf.. The NR activity in leaves and roots of different citrus rootstocks receded with P levels decreased significantly. The APase activity in leaves and roots, and the SAPase activity in roots was all in the order of C. ichangensis Swingle＞C. limonia Osbeck＞C. aurantium L. ＞P. trifoliata Raf. under low P stress. The I_max of C. ichangensis Swingle was greater than C. limonia Osbeck , C.aurantium L. and P. trifoliata Raf. under low P conditions, while the K_m and C_min was smaller than C. limonia Osbeck, C. aurantium L. and P. trifoliata Raf.【Conclusion】The ability to endure to low P stress of C. ichangensis Swingle was much stronger, and response of root morphology and physiological adaptation mechanisms were more obvious than the other three kinds of citrus rootstocks under low P conditions, which showed strong absorption characteristics of P dynamics.

Response of Yield and Leaf Photosynthesis to Sink-Source Ratio Altering Demand in Olive

ZHU Zhen-jia, JIANG Cheng-ying, SHI Yan-hu, WU Wen-jun, CHEN Nian-lai

Scientia Agricultura Sinica. 2015, 48(3):  546-554.  doi:10.3864/j.issn.0578-1752.2015.03.14

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【Objective】In order to more clearly understand the mechanism of source leaf photosynthesis response to sink-source ratio alteration, the gas exchange rates, chlorophyll a fluorescence kinetics and leaf carbohydrate content in a long-term (125 days after treatment) response to sink-source ratio alteration and their relationships in olive were investigated.【Method】Long-term response of gas exchange, chlorophyll a fluorescence and leaf carbohydrate was measured by using flowers removal and partial defoliation techniques at pre-flowering stages on two years old shoots of ‘Ezhi 8’ olive (Olea europaea L.) trees.【Result】The results showed that defoliation significantly reduced fruit weight and fruit setting, and flowers removal only significantly increased fruit fresh weight. In a short term (7 days after treatment) after source sink ratio decreased, soluble sugar, starch and non-structural carbohydrate content in leaves increased significantly, the source leaves net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E) decreased significantly, the intercellular CO₂ concentration increased significantly, PSII maximum photochemistry efficiency (F_v/F_m) decreased dramatically, PSII photochemistry efficiency(ΦPSⅡ), photochemical quenching coefficient (qP) decreased significantly, non photochemical quenching coefficient (NPQ) increased significantly. Thirty days after treatment, there was no significant difference in the contents of soluble sugar, starch and non-structural carbohydrate among three treatments, while it was still exist difference of Pn, Gs, E, ΦPSⅡand NPQ among those. Sixty days after treatment, difference in most parameters of gas exchange and chlorophyll fluorescence between control and defoliation treatment was eliminated, but Pn, Gs, E, Ciand ΦPSⅡ in flowers removal treatment were also significantly different from the controls ones. One hundred and twenty-five days after treatment, soluble sugar and starch content and most parameters of gas exchange and chlorophyll fluorescence in defoliation treatment significantly decreased, however, ΦPSⅡin flowers removal treatment was also significantly lower than the control, Ciwas also significantly higher than the control. In a 125-day period after treatment, there was a significant positive correlation between Gs and Pn (P＜0.01), between E, F_m, ΦPSII and Pn (P＜0.05), and there was no significant correlation between Ci, NSC and Pn.【Conclusion】In the long-term response of gas exchange, chlorophyll a fluorescence and leaf carbohydrate to sink-source ratio alteration,PSII photochemistry efficiency (ΦPSⅡ) may be the main reason for the decrease of Pn, rather than the result of feedback inhibition of leaf carbohydrate accumulation. Defoliation can improve olive leaf photosynthetic capacity in a short term, but it will accelerate leaf senescence.

STORAGE·FRESH-KEEPING·PROCESSING

Association Analysis Between Part Nutritional Compositions and Taste of Purple-Fleshed Sweetpotato

SHEN Sheng-fa, WU Lie-hong, LI Bing

Scientia Agricultura Sinica. 2015, 48(3):  555-564.  doi:10.3864/j.issn.0578-1752.2015.03.15

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【Objective】 The aim of this research is to define the edible quality index and to provide a basis for edible purple-fleshed sweetpotato breeding. 【Method】 The content of anthocyanin, dry matter, soluble sugar and reducing sugar in steamed root, and taste index were measured from 276 purple sweetpotato strains. In addition, the relationships between nutritional compositions and taste of steamed purple sweetpotato were analyzed. 【Result】 As the great variation coefficient of anthocyanin content, it is easy to screen high anthocyanin content varieties in purple sweetpotato breeding. It is the best method that ayamurasaki was crossed with non-purple-fleshed parents containing high sugar to improve the taste of filial purple-fleshed F1 generation of ayamurasaki. Reducing the group level of anthocyanin content would benefit to improve the breeding efficiency of edible purple-flesh sweetpotato. Even thoughanthocyanin content leass than 90 mg·100g^-1FW, there was still a good breeding efficiency of edible purple-flesh sweetpotato with high anthocyanin content. There was a better efficiency of edible purple-fleshed breeding when dry matter content ranged from 27.5% to 38%, whereas the best breeding efficiency for dry matter content was ranged from 32% to 36.5%. Moreover, increasing the group level of soluble sugar content in steamed root would help to improve the efficiency of edible purple-fleshed breeding. Anthocyanin content showed highly significant negative effects on sweetness and fragrance of purple sweetpotato, and its negative effects on taste up to 51.30% of taste incremental contribution from soluble sugar. Dry matter content was highly significantly positively correlated with texture, fragrance, and coarse fiber of purple sweetpotato, but it was highly significantly negativelycorrelated with viscosity, and was closely significantly negatively correlated with sweetness. Therefore, dry matter content was little influence on total taste. On the other hand, soluble sugar in steamed root showed a significant effect on taste of purple sweetpotato, in which soluble sugar content had a highly significantpositive correlationwithsweetness,viscosity and texture. Furthermore, non-reducing sugar content had more contribution to sweetness, fragrance, and texture than reducing sugar content, and the contribution to taste incremental from non-reducing sugar was 2.3 times than that of the reducing sugar content. Sweetnessoccupiedan extremely important positionin the taste evaluation ofpurple sweetpotato, and its contributionrate of taste increment was up to 55.38%.【Conclusion】The content of anthocyanin and soluble sugar in steamed root is an important index for edible purple-fleshed varieties.In conclusion, it should take into account both nutrition andfood quality in edible purple-fleshed breeding, and anthocyanin content should be controlledless than90 mg·100g^-1FW. The best way for traditional edible purple-fleshed sweetpotato breeding is to select purple-fleshed parent hybrid with high sugar-containing non-purple-fleshed parent.

ANIMAL SCIENCE·VETERINARY SCIENCERE

The Disaster, Ecological Distribution and Control of Poisonous Weeds in Natural Grasslands of Xinjiang Uygur Autonomous Region

YAN Du-jian, ZHOU Qi-wu, LU Hao, WU Chen-chen, ZHAO Bao-yu, CAO Dan-dan, MA Feng, LIU Xiao-xue

Scientia Agricultura Sinica. 2015, 48(3):  565-582.  doi:10.3864/j.issn.0578-1752.2015.03.16

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Natural grassland is the material basis for the development of husbandry in the minority area, and it is also a very important component to maintain the balance of natural ecological environment in Xinjiang. For a long time, because of drought, severe overgrazing, blind reclamation, population increase and other natural and man-made factors, as well as inadequate infrastructure construction and lagging management of the grass, high-quality forage is decreasing year by year and poisonous weeds are fast spreading, leading to grasslands reverse succession and contagious poisonous weeds, widespread desertification, destroying the balance of natural ecological environment, and a large number of livestock poisoning even death due to grazed poisonous weeds mistakenly. Especially in recent decades, the rapid spreading of poisonous weeds have caused the reduction of grassland vegetation and biodiversity, the simplification of vegetation, decline of grass yield, and the degeneration of natural grassland with edible pasture grass, instead of more different levels of degraded grasslands even severe contagious poisonous weeds. In some regions, the grassland poisoned has led to the poisonous grass disaster take place frequently, even broke out, which have increased from the basic ecological problem to a social problem, seriously affected the local social stability and grassland ecological security. At present, more than 85% available natural grasslands are degenerating to a greater or lesser extent and 37.50% of them are severely degraded, with an poisonous weeds disaster area of nearly 700 million hm², which has accounted for 20.42% of the total hazard area of natural grassland of the country, and the annual death number of animals with poisoning is more than 3000 in average . Xinjiang natural grassland contains common poisonous plants of 81 species, 24 families and 54 genera. Among them, the Aconitum carmichaeli, Aconitum soongaricum, Achnatherum inebrians, Oxytropis glabra, Astragalus variabilis, Anabasis aphylla, Pedicularis, Ligularia sibirica and Cucuta virosa are more serious harmful poisonous weeds to grassland animal husbandry, which accounted for approximately more than 80% of the total poisonous weeds hazard area. Therefore, a comprehensive understanding of poisonous weeds disaster situation in natural grassland of Xinjiang, weed species and geographic distribution, the effective prevention and control, the solution of the poisonous weeds disaster, is of great significance to improve the grassland productivity and forage quality, promote the sustainable development of animal husbandry in pastoral areas and farmers’ income, flourishing frontier minority economy and stabilize the ecological environment balance. According to the analysis and summary of data reported and results of the project group actually investigated in Xinjiang natural grasslands, the disaster situation, species of poisonous weeds and geographical distribution, prevention and control measures and reasonable utilization are reviewed. The disaster condition of regional grassland ecological and animal husbandry production caused by the poisonous grass, main poisonous grass species, geographic distribution and damage area of natural grassland in Xinjiang is summarized, respectively. At the same time, on the basis of the project team dedicated to the prevention and control of the China’s western poisonous grass research for many years, the existing problems and reasons of poisonous grass varieties, severe disasters, difficulty of prevention and treatment in natural grassland of Xinjiang were analyzed. The authors put forward some thoughts that from the angle of the ecology, the traditional control idea should be changed to strengthen the research of poisonous plant biology, ecology, toxicology characteristics, prevention and control of poisoning disease as well as comprehensive utilization etc. Thus it is helpful for us to understand the scientific poisonous weeds. Based on the principle of “change harm into good, make waste profitable”, place equal stress on ecological protection and development and utilization, study and learn from the successful technologies in prevention and control of poisonous plants in developed countries such as USA, take comprehensive prevention and control technology that ecological control means combined with other multiple methods to prevent poisonous weeds disaster, thus providing people with the basic information to know and research of the main poisonous weeds in natural grasslands in Xinjiang.

Impact of Concentrations and Immune-stimulating Times of Poly I:C on Gene Expression of Porcine Peripheral Blood Mononuclear Cells

WANG Ji-ying, WANG Yan-ping, WANG Huai-zhong, WANG Hai-fei, LIU Jian-feng, GUO Jian-feng

Scientia Agricultura Sinica. 2015, 48(3):  583-593.  doi:10.3864/j.issn.0578-1752.2015.03.17

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【Objective】 Polyinosinic:polycytidylic acid (Poly I:C) is a synthetic double-stranded polyribonucleotide. As an analogue of viral double-stranded RNA, Poly I:C is widely used as immunologic stimulant to study the immune regulation and inflammatory reaction of an organism to the RNA viruses. So far, no studies were reported on determination of the optional concentration and stimulating time of porcine peripheral blood mononuclear cells (PBMC) in response to Poly I:C stimulation. In the present study, we systematically analyzed the impact of Poly I:C concentrations and stimulating times on the expression of several cytokines and pattern recognition receptors and the optional concentration and stimulating time of Poly I:C in the PBMC were determined, which would provide an experimental foundation for the future use of Poly I:C and porcine PBMC to study the immune response of pigs to RNA viruses. 【Method】 Using isolated PBMC and 1:5 EDTA-anticoagulated diluted blood of three Landrace piglets, the in vitro immune stimulating experiment was performed with a series of Poly I:C concentrations (0, 10, 20 and 40 μg·mL^-1) and immune-stimulating culture times (4 h, 8 h, 12 h and 24 h). The expression of several cytokines (IL6, IL8, TNFα, IL10, IRF3, IFNα and IFNγ) and pattern recognition receptors (TLR3 and TLR4) were determined by qPCR. According to the relative expression trends of these cytokines and receptors, it was analyzed to achieve the optimal Poly I:C concentration and immune-stimulating culture time. 【Result】 The expression of the cytokines and receptors were affected by Poly I:C concentrations as well as immune-stimulating times. Each gene had its characteristic expression trend, and varied in Poly I:C concentration and immune-stimulating time to attain the highest expression. For the two interferon genes, IFNα and IFNγ, the highest expressions were observed when the stimulating time was 4 h, and their expression decreased gradually with the stimulating time. For the other five cytokines (IL6, IL8, TNFα, IL10 and IRF3) and two receptor genes (TLR3 and TLR4), the expressions were gradually increased with the Poly I:C concentrations and stimulation times, and reached the highest when Poly I:C concentrations and stimulation times were 20-40 μg·mL^-1 and 12-24 h, respectively. However, for the genes whose expressions were highest when Poly I:C concentration and stimulation time were 20 μg·mL^-1 and 12 h, their expressions showed small decline when Poly I:C concentration and stimulation time were 40 μg·mL^-1 and 24 h. Furthermore, in the study, it was also tested the expressions of the above genes of 1:5 EDTA-anticoagulated diluted blood in response to various Poly I:C concentrations and stimulation times. The results indicated that the whole expressions of these genes were lower than those in PBMC, especially for two interleukin genes, IL6 and IL8, whose expression in diluted whole blood was not only low but the variation trends with Poly I:C concentrations and stimulation time were reversed with those in PBMC. Compared with PBMC, though diluted blood preserved the integrity of the immune state of the pig’s blood, the major drawback is that the anticoagulant is kept in it. The anticoagulant used in the study was EDTAK2, which can combine with calcium ion to form chelate, so as to prevent blood clotting. However, calcium ion is an important signal molecule in cells, and the combination of calcium ion with EDTA may have a certain impact on the subsequent cell function. In addition, some of the compounds and plasma proteins in whole blood may be also involved in the regulation of immune cells to Poly I:C immune stimulation so as to reduce immune response. 【Conclusion】 Comprehensive analysis of the expression trends of the cytokines and receptors were detected, and it was concluded that, in the porcine PBMC stimulation experiment using Poly I:C, the optimal concentration and immune-stimulating time are 20 μg·mL^-1 and 24 hours, respectively. EDTA- anticoagulated diluted blood has less immune response to Poly I:C and different variation trends with Poly I:C concentrations and stimulation times.

Rethinking the Withdrawal of Antimicrobial Growth Promotants in Animal Feed

HAO Hai-hong, CHENG Gu-yue, DAI Meng-hong, WANG Xu, WANG Yu-lian, HUANG Ling-li, LIU Zhen-li, YUAN Zong-hui

Scientia Agricultura Sinica. 2015, 48(3):  594-603.  doi:10.3864/j.issn.0578-1752.2015.03.18

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Withdrawal of antimicrobial growth promotants (AGPs) in animal feed issued by European Union (EU) countries caused widespread controversy in the international community. This paper comprehensively reviewed the antimicrobial resistance monitoring data from animal original bacteria and the risk assessment results of veterinary usage. After profoundly rethinking the ban of AGPs in animal feed, the results showed that (1) the risk of some AGPs (e.g. macrolide AGP of tylosin and streptogramin AGP of virginiamycin) seemed to be overstated. The risk of the usage of macrolide AGPs in food animals to emergence of macrolide resistant Campylobacter in human is negligible, and the use of virginiamycin as AGPs could hardly affect the treatment of human infections caused by Enterococcus; (2)There is a lack of scientific evidence for supporting the proposition of transmission of antimicrobial resistance from farm to dining table. Although there are some evidence that antimicrobial resistant bacteria could directly transmit from food animal to those persons who closely contacted with animals, there is no direct and sufficient evidents to support the transfer of antimicrobial resistant pathogens through food chain to persons; (3) Withdrawal of AGPs did not change the epidemiology of resistant pathogens, especially for the avoparcin in glycopeptides, enrofloxacin in fluoroquinolones and chlorotetracycline in tetracyclines. After ban of these three classes of AGPs, the number of resistant bacteria from both animal and human continued to increase. The reason may be attributed to the enhanced fitness of fluoroquinolone resistance in Campylobacter and the increase of the consumption of therapeutic tetracycline agents; (4) Withdrawal of the AGPs may brought a certain loss for the animal breeding industry. For example, it may increase the incidence of necrotizing enteritis caused by Clostridium, increase therapeutic use of antimicrobial agents in the farmed animals, and increase breeding materials and corresponding venues, etc.; (5) Withdrawal of the AGPs may cause a certain influence on animal food safety and human public health. For instance, it may affect the fermentation of animal intestinal flora and thereby increase the emissions of harmful gas. It may increase the chances of bacteria contamination during food processing and therefore increase the incidence of foodborne pathogens in human. Conclusively, the political decision must be developed based on the balance of pros and cons and the adjustment of spatial and temporal condition. It also need to comprehensively consider the function of withdrawal of AGPs on control of antimicrobial resistance and the influence of withdrawal of AGPs on the animal breeding industry and human public health. Face the development of animal breeding industry in China and the world food sustainable needs, it is necessary to conduct in-depth research and systemic risk assessment to find new and rational strategy to control resistance. It is also essential to strengthen the government supervision to avoid drug abuse and promote the rational use of antimicrobial agents in food animals.

RESEARCH NOTES

QTL Analysis of Na⁺ and K⁺ Concentrations in japonica Rice   Under Salt and Alkaline Stress

XING Jun, CHANG Hui-lin, WANG Jing-guo, LIU Hua-long, SUN Jian, ZHENG Hong-liang, ZHAO Hong-wei, ZOU De-tang

Scientia Agricultura Sinica. 2015, 48(3):  604-612.  doi:10.3864/j.issn.0578-1752.2015.03.19

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【Objective】Salinization and alkalinization of soil are becoming worse and worse during these years, and the concentrations of Na⁺, K⁺ and Na⁺/K⁺ ratio could be taken as the criterial indicators of saline-alkali tolerance in plant. Therefore, the QTL analysis of Na⁺, K⁺ concentration and Na⁺/K⁺ ratio in shoots and roots of rice at the seedling stage under salt or alkaline stress were conducted in the present study in order to provide a scientific basis for the rice genetic mechanism of salt and alkaline tolerance and molecular marker assisted breeding. 【Method】 The recombinant inbred line (RIL) population derived from a cross Dongnong 425 (high yield and quality) as the female parent and Changbai 10 (salt tolerance) as the male parent. A genetic linkage map was constructed with 102 SSR markers, covering 1 915.05 cM of rice genome at an average interval of 18.77 cM. The concentrations of Na⁺, K⁺ and Na⁺/K⁺ ratio in shoots and roots were phenotyped under 140 mmol·L^-1 NaCl of salt stress and 0.15% Na₂CO₃ of alkali stress at seedling stage. The correlation analysis by using SPSS v19.0 program and QTL analysis by using QTL IciMapping v3.3 program of the complete interval mapping method were conducted.【Result】The Na⁺ and K⁺ concentrations in shoots were higher than in roots under salt and alkaline stress in both the parents and RILs. All traits almost presented gaussian distribution, conforming typical genetic model of quantitative traits and the requirements of the QTL mapping. The results of correlation analysis showed that the concentrations of Na⁺ and K⁺ had a significant positive correlation in shoots and roots under salt and alkali stress, whereas there was no significant correlation between salt and alkali stress. A total of fifteen QTLs were detected under salt and alkaline stress, QTLs are located on different chromosomes between salt and alkali stress. Five QTLs were detected under salt stress, including one QTL associated with the concentration of K⁺ in shoots, which was located on chromosome 8 in the marker interval RM1308-RM281, explained 6.83% of phenotypic variance. Three QTLs associated with the concentration of Na⁺ in roots, which were located on chromosome 3 and 8, of which, qSRNC3-1 explained the maximum (16.41%) of phenotypic variance. One QTL associated with the concentration of K⁺ in roots, explained 3.52% of phenotypic variance. No QTL were found to be associated with the concentration of Na⁺, Na⁺/K⁺ ratio in shoots, and Na⁺/K⁺ ratio in roots. A total of ten QTLs were detected under alkali stress, including one QTL associated with the concentration of Na⁺ in shoots, which was located on chromosome 2 in the marker interval RM1347-RM48, explained 14.41% of phenotypic variance; One QTL associated with the concentration of K⁺ in shoots was located on chromosome 2 in the marker interval RM1255-RM213. Three QTLs associated with the Na⁺/K⁺ ratio in shoots, which were located on chromosomes 2, 7 and 10, respectively, of which, qASNK2 explained 7.57% of phenotypic variance. One QTL associated with the concentration of Na⁺ in roots, which was located on chromosome 3 in the marker interval RM293-RM232, explained 13.71% of phenotypic variance. Two QTLs associated with the concentration of K⁺ in roots, which were located on chromosome 1 in the marker interval RM5-RM9 and chromosome 2 in the marker interval RM12865-RM12941, respectively. Two QTLs associated with Na⁺/K⁺ ratio in roots, which were located on chromosome 3 and 4, of which, qARNK3 explained 10.48% of phenotypic variance. By comparing the mapping results, most of the detected QTLs were in the same or adjacent chromosomal regions of previously reported QTLs for tolerance to salt and alkali stress. In addition, two QTLs, namely qASKC2 and qARKC2, were not reported in previous studies, implying the possibility to be new QTL for tolerance to alkali.【Conclusion】The uptake and transport of the Na⁺ and K⁺ were considered to be parallel and independent under salt and alkali stress. The uptake of Na⁺ and K⁺ in roots and the transport in shoots had different genetic mechanism. The concentrations of Na⁺ and K⁺ between salt and alkali stress were independently inherited.

Detection of Strawberry mild yellow edge virus by RT-LAMP

CHEN Liu, SHANG Qiao-xia, CHEN Xiao-yu, XING Dong-mei, RAN Ce, WEI Yan-min, ZHAO Xiao-yan, LIU Zheng-ping

Scientia Agricultura Sinica. 2015, 48(3):  613-520.  doi:10.3864/j.issn.0578-1752.2015.03.20

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【Objective】Strawberry mild yellow edge virus (SMYEV) is an important virus infecting strawberry plants, reducing fruit yield and quality. The objective of this study is to establish an effective method to detect SMYEV using the reverse transcription loop-mediated isothermal amplification (RT-LAMP). 【Method】 Four specific RT-LAMP primers for SMYEV detection including SMYEV-FIP (5′-CAGATCAGCGACAATTTGGACTCCTGAGGAACTTGCTGCT-3′), SMYEV-BIP (5′-GCTTTGTCGGGGATC CTGGGAAGGCTAAGTCGAAGAGACC-3′), SMYEV-F3 (5′-TCAAGTTGGTGACCCTTTCC-3′) and SMYEV-B3 (5′-CGAGG AACCAATGTCGTAGC-3′) were designed according to the published 3′ end conservative sequences of SMYEV CP gene. Different reaction temperatures (60, 61, 62, 63, 64, 65℃), reaction times (30, 45, 60, 75 min), concentrations of primers SMYEV-FIP/BIP (1.0, 1.2, 1.4, 1.6, 1.8 µmol?L^-1) and SMYEV-F3/B3 (0.1, 0.15, 0.2, 0.25, 0.3 µmol?L^-1), Mg²⁺ (2, 4, 6, 8, 10 mmol?L^-1), dNTPs (0, 0.4, 0.8, 1.2, 1.6, 2.0 mmol?L^-1), betaine (0, 0.4, 0.8, 1.0, 1.2, 1.4 mol?L^-1) and DTT (2.0, 2.4, 2.8, 3.2, 3.6, 4.0 µmol?L^-1) were used and optimized in the RT-LAMP in order to improve specificity and sensitivity of the detection. The specificity of RT-LAMP was tested by using different RNA templates from other important strawberry viruses and healthy leaves of strawberry plants. The sensitivities of RT-LAMP and RT-PCR for detecting SMYEV were compared by using ten-fold serially diluted RNA templates of SMYEV (including original RNA, 10^-1, 10^-2, 10^-3, 10^-4, 10^-5, 10^-6 and 10^-7 dilution). The RT-LAMP products could be detected by electrophoresis and ultraviolet image technology, the typical ladder-like pattern was observed in the positive samples while no amplification of DNA was visible in the negative samples. The RT-LAMP products could be also evaluated by adding SYBR green I, the color of the product for the positive reaction changed from orange to green while the product for a negative reaction remained orange.【Result】The specific RT-LAMP method to detect SMYEV was established and the optimal amplification was achieved by incubation of 1.0 µmol?L^-1 SMYEV-FIP/BIP, 0.1 µmol?L^-1 SMYEV-F₃/B₃, 4 mmol?L^-1 Mg²⁺, 1.6 mmol?L^-1 dNTPs, 0.4 mol?L^-1 betaine, 2.0 µmol?L^-1 DTT with template RNA at 60℃ for 45 min. The detection specificity of RT-LAMP was tested by using different RNA templates from SMYEV, Strawberry vein banding virus, Strawberry mottle virus, Strawberry crinkle virus and leaf sample of healthy strawberry plant. The optimized RT-LAMP method had high sensitivity that only reaction within SMYEV RNA template could produce typical ladder-like bands tested by electrophoresis and UV. Test results of RT-PCR detection were positive only with original and 10^-1, 10^-2, 10^-3 diluent RNA templates and no amplified band could be detected when using diluent RNA template with the increase of dilution ratio. While in RT-LAMP detection positive results could be observed with original, 10^-1, 10^-2, 10^-3, 10^-4, and 10^-5 diluent RNA templates. Sensitivity of the RT-LAMP was 100 times higher than the RT-PCR method for detecting SMYEV. It was time-saving and the results could be directly observed in RT-LAMP which are suitable for SMYEV detection.【Conclusion】 The optimized RT-LAMP proved to be a faster, simpler and specific method for SMYEV detection and could be applied in the process of seedling breeding, field investigation and customs quarantine control in both research institutions and rural areas.