Scientia Agricultura Sinica

Function Analysis of a Drought Stress Induced MYB Transcription Factor GhRAX3 in Cotton

DING Zhen-qian, CHEN Tian-zi, LIU Ting-li, LIU Xiao-shuang, ZHANG Bao-long, ZHOU Xing-gen

Scientia Agricultura Sinica. 2015, 48(18): 3569-3579. doi:10.3864/j.issn.0578-1752.2015.18.001

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【Objective】 Cloning and function analysis of MYB transcription factor in response to drought stress were conducted to understand cotton tolerance to drought stress and its further application in cotton breeding.【Method】With a drought induced GbMYB5 as a query, BLASTX search in the non-redundant protein sequences (nr) database in NCBI was performed to search possible drought induced MYB transcription factors in cotton. Real time PCR confirmed that a MYB transcription factor GhRAX3 responded to drought stress. The agro-infiltration based transient expression of a fused GhRAX3-GFP4 in tobacco cell was used to detect subcellular localization of GhRAX3. A virus induced gene silencing system mediated by cotton leaf crumple virus was used to depress the expression of GhRAX3 in cotton, and the water loss rate, relative water content, total antioxidant activity, malondialdehyde content and electrolyte leakage in leaves of GhRAX3-silenced cotton were subsequently investigated as well as their phenotypes in response to drought stress. 【Result】BLASTX with GbMYB5 as a query revealed that GhRAX3, which encodes an R2R3-MYB transcription factor, had a query cover of 38% and a identity of 79%. GhRAX3 was quickly responded to the induction of 18% (v/v) PEG 6000 by up-regulating 5-fold at 0.5 h post PEG 6000 treatment and up to 33-fold at 24 h post PEG 6000 treatment. The subcellular localization of the fused GhRAX3-GFP4 in tobacco cell indicated that GhRAX3 was located in the cell nucleus. When subjected to virus induced gene silencing, the expression level of GhRAX3 was depressed to 41% of the normal level. The water loss rate in the detached leaves of GhRAX3 silencing (viz. VIGS) cotton plants was significantly higher that those in the wilt type (WT) and the empty vector agro-infiltrated (EM) cotton plantlets during the 0-7 h duration after detaching. Under the 18% (v/v) PEG 6000 treatment for 24 h or water-withhold for 15 d, theVIGS cotton plantlets showed a more severe wilt symptom when compared with the WT and the EM cotton plantlets. At 7 d post water-withhold treatment, the relative water contents, total antioxidant activity, malondialdehyde content and electrolyte leakage in leaves were further investigated in the VIGS, WT and EM plants. The relative water content and total antioxidant activity in the VIGS plants was 82% and 1.29 U·mg^-1protein, respectively. By contrast, the relative water content in the WT and EM plants was 89% and 91%, respectively. And the total antioxidant activity in the WT and EM plants was 3.44 U·mg^-1 protein and 3.19 U·mg^-1 protein, respectively. The relative water content and total antioxidant activity in the VIGS plants were significantly lower than those in the WT and EM plants. The electrolyte leakage and malondialdehyde content in the VIGS plants was 78.54% and 74.20 nmol·mg^-1 FW, respectively. While the electrolyte leakage in the WT and EM plants was 44.98% and 47.45%, respectively. And the malondialdehyde content in the WT and EM plants was 44.90 nmol·mg^-1 FW and 47.29 nmol·mg^-1 FW, respectively. The electrolyte leakage and malondialdehyde content in the VIGS plants were significantly higher than those in the WT and EM plants. 【Conclusion】GhRAX3 was responded to drought stress. The depression of GhRAX3 compromised the tolerance of cotton plants to drought stress as a result of significant decrease in relative water content and total antioxidant activity and a significant increase in the electrolyte leakage and malondialdehyde content under drought stress.

Cloning and Function Analysis of Salicylic Acid Binding Protein Gene GmSABP2 from Soybean

JIA Ya-jun, WANG Xiao-ting, XU Na, GUO Na, XING Han

Scientia Agricultura Sinica. 2015, 48(18): 3580-3588. doi:10.3864/j.issn.0578-1752.2015.18.002

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【Objective】The aim of this study is to clone and analyze soybean protein gene GmSABP2, which is binded with salicylic acid, and transform Arabidopsis for analyzing salt tolerance and drought tolerance, and further understand the molecular mechanism of salt tolerance and drought-resistance of the gene. 【Method】 Using SABP2 as a probe, the soybean genome database was searched, and the highest sequence homology was picked out and named as GmSABP2. The gene GmSABP2 was cloned by using electronic cloning technology. The DNAMAN program was used to analyze the amino acid sequence alignment and the conserved domain amino acid by the CD-search conducted NCBI. The MEGA program was applied to make the phylogenetic analysis. The phenotypic variation of soybean seedlings under salt and drought stress was analyzed. The expression of the characteristics of GmSABP2 under salt and drought conditions was analyzed by Real time-PCR of soybean seedlings. Gateway technology was used to build plant expression vector pEarleyGate103-GmSABP2, shifted into Agrobacterium tumefaciens EHA105, infected Arabidopsis by utilizing flower dip method, then the homozygous transgenic plants were obtained by resistance screening and finally the salt and drought tolerance was analyzed. The wild-type plants and transgenic plants were treated under salt and drought stresses, and both the seed germination, root length and mature plants were counted under stress conditions. 【Result】The cDNA sequence of GmSABP2 was obtained and the open reading frame is 786 bp and total length of the sequence is 1 235 bp, encoding 261 amino acids. And molecular weight is 29.15 kD, an isoelectric point is 5.58. The amino acid sequence alignment and phylogenetic analysis showed that GmSABP2 and tobacco SABP2, Rauvolfia serpentina PNAE had the highest similarity. Using the CD-search of NCBI, it was found that the Abhydrolase_6 (pfam: 12697) as conserved domain hydrolases. Soybean SABP2 protein belongs to SABP2 α/β hydrolase superfamily. Using MEGA program to build a system of species multiple phylogenetic tree, it was found that SABP2 of soybeans, Theobroma cacao SABP2 and Solanum lycopersicum SABP2 have a close genetic relationship, but has a distant genetic relationship with Arabidopsis SABP2. The phenotype of soybean seedlings under salt and drought conditions was analyzed and it was found that there were significant stress effects. Real time-PCR analysis showed that GmSABP2 under salt and drought conditions were upregulated expression. Arabidopsis thaliana resistance analysis showed that under normal culture conditions, the wild-type plants and transgenic plants could germinate and grow. Under 150 mmol·L^-1 NaCl treatment conditions, seed germination rate of wild-type plants was 38%, seedling root length after 12 days was 0.4 cm and the survival rate of mature plants was 49%; The seed germination rate of transgenic lines was 67%, seedling root length after 12 days was 1.1 cm and mature plants survival was 78%. Under 20% PEG6000 treatment conditions, the seed germination rate of wild-type plants was 31%, seedling root length after 12 days was 0.5 cm and mature plants survival rate was 36%; The seed germination rate of transgenic lines was 57%, seedling root length after 12 days was 1.0 cm and mature plants survival rate was 66%.【Conclusion】 The GmSABP2 gene increases the resistance of Arabidopsis plants under salt and drought conditions.

Effects of Mulching on Grain Yield and Water Use Efficiency of Dryland Wheat in Different Rainfall Years

GAO Yan-mei, SUN Min, GAO Zhi-qiang, CUI Kai, ZHAO Hong-mei, YANG Zhen-ping, HAO Xing-yu

Scientia Agricultura Sinica. 2015, 48(18): 3589-3599. doi:10.3864/j.issn.0578-1752.2015.18.003

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【Objective】 In order to find out the effects of mulching in a fallow period on water storage and high production and to investigate the effects of mulching in a growth period on water-saving and yield promotion, find a new technique of dryland water retention through mulching in a fallow period and growth period in different rainfall years. 【Method】 The experiment was carried out from 2011 to 2014 years in Wenxi, Shanxi province, and utilized the split-plot design with mulching methods in a fallow period as the main plots and sowing patterns in a growth period（FM and DS）as subplots, to study the effects of mulching on soil water storage at the depth of 0-300 cm , wheat yield components, water use efficiency, water-saving, and yield promotion.【Result】Compared with no mulching treatment, mulching in a fallow period improved the soil water storage at the depth of 0-300 cm at the sowing stage. It was increased 40-41 mm in a humid year, 55-58 mm in a normal year, and 70 mm in a dry year, and more water was stored in deep layers in a dry year. Mulching in a fallow period increased water storage efficiency in a fallow period by more than 20% in different rainfall years, and its effects of water-saving lasted from the sowing stage to the booting stage, and the FM in the growth period had better effects. Compared with no mulching treatment, mulching in a fallow period increased wheat spike number, yield, and water use efficiency significantly, yield was improved more than 20%, while water use efficiency was improved more than 15%. With mulching in a fallow period and FM in a growth period, wheat grain number per spike and 1000-grain weight increased significantly. The result also showed that with mulching treatment in a fallow period, soil water in sowing period increased 1 mm can improved the yield by 21-27 kg·hm^-2 in a humid year, 16-18 kg·hm^-2 in a normal year and 13-24 kg·hm^-2 in a dry year, and at the condition of mulching in fallow period, FM in a growth period had better effects on yield improving. FM in a growth period could improve the effects of water-saving and yield promotion, the water saved in a per kilo gram of grain was improved more than 10%, and the yield increased more than 11% when consuming 1 mm soil moisture. 【Conclusion】Mulching in a fallow period of dryland wheat was beneficial for water storage and rainfall conservation during a fallow period, and it had a better effect in a dry year. Mulching in a fallow period can improve soil water storage before anthesis and increase yield mainly by increasing spike number, and FM in growth period had a better effect. Mulching in a fallow period was conducive to improve soil water storage and yield. When the soil moisture in the sowing period was sufficient, mulching in the growth period was beneficial for improving water-saving and yield. When the soil moisture was insufficient, mulching in the growth period would result in wasting water and decreasing yield.

Evaluation of the Effect of Co-Inoculant of Paenibacillus mucilaginosus and Bradyrhizobium japonicum in Application

MA Ming-chao, LIU Li, JIANG Xin, GUAN Da-wei, LI Jun

Scientia Agricultura Sinica. 2015, 48(18): 3600-3611. doi:10.3864/j.issn.0578-1752.2015.18.004

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【Objective】Paenibacillus mucilaginosus and Bradyrhizobium japonicum are widely used as microbial fertilizers in agricultural application due to their beneficial properties, such as phosphorus-solubilization, potassium-release, growth-promotion, and symbiotic nitrogen fixation, respectively. They have all attracted considerable attention of researchers on their application effects and mechanisms when they were used as a single inoculation. The aim of this paper is to evaluate the effects of both species on soybean and reveal the mechanisms in order to provide certain theoretical supports for new multiple species inoculants of microbial fertilizers. 【Method】A field experiment with five different fertilizing measures was carried out in Taian, Shandong Province, including T1 (the control), T2 (inoculant of P. mucilaginosus 3016), T3 (inoculant of B. japonicum 5136), T4 (co-inoculant of P. mucilaginosus 3016 and B. japonicum 5136) and T5 (the regular fertilizer dose). Four replicates for each treatment were designed. The effects on soybean growth, soil fertility and soil microbiological characteristics were analyzed.【Result】The results showed that inoculant of P. mucilaginosus 3016 and/or B. japonicum 5136 could improve seeds weight per plant, crop yield and harvest index, and T4 treatment was the highest and better than T1 with a rate of 12.8%, 9.3% and 41.0%, respectively. Co-inoculant could keep the N, P, K content in seeds, stems and leaves of soybean with the highest level, especially K of seeds, N and P of stems and leaves, which were increased by 5.7%, 9.3% and 38.5%, respectively. Co-inoculant could increase the soybean yield and quality. In terms of soil fertility, bio-fertilizer and chemical fertilizer could improve the content of total N, available P, available K and organic matter in soil to some extent, and bio-fertilizer was better at persistence and less effect on soil pH. In this field experiment, the soil fertility in T4 treatment was the best, with an increase rate of 6.5%, 43.7%, 8.5% and 15.5% for total N, available P, available K and organic matter than that in T1 treatment. Co-inoculant could improve soil fertility. Meanwhile, co-inoculation could change soil from “fungus type” to “bacteria type”, by increasing the quantity of bacteria and actinomycete, and inhibiting fungi, which lead to a healthy soil structure. The results of Canonical Correlation Analysis (CCA) showed that pH and available K played a key role in the shifts of microbial community.【Conclusion】Co-inoculant of P. mucilaginosus 3016 and B. japonicum 5136 not only increased the soybean quality and crop yield, but also improved soil microbiome and soil fertility. That may be an optimal fertilizing measure with good application prospects and popularized value.

Occurrence Status and Future Spreading Areas of Maize Gray Leaf Spot in China

ZHAO Li-ping, WANG Xiao-ming, DUAN Can-xing, LONG Shu-sheng, LI Xiao, LI Hong-lian, HE Yue-qiu, JIN Qi-ming, WU Xiao-fei, SONG Feng-jing

Scientia Agricultura Sinica. 2015, 48(18): 3612-3626. doi:10.3864/j.issn.0578-1752.2015.18.005

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【Objective】The objective of this study is to understand the occurrence status of maize gray leaf spot (GLS) in China, and to predict its spreading areas in near future. It is an important basis for protecting maize production.【Method】The strains isolated from samples of GLS in new areas where were not reported for GLS were identified by using morphologic, cultural characteristics and molecular identification techniques. The occurrence site data of GLS during 2004-2014 were summarized for detailed clearing the status of GLS distribution in China, and monsoon character was analyzed for speculating the spreading lines of GLS before 2014 and in the future.【Result】The strains from Guizhou and Sichuan were identified as Cercospora zeina, and the species C. zeae-maydis was identified in Hebei. Two species were found in strains from Shaanxi and Henan. GLS has been found in fifteen provinces in China and was severe in southwest areas. By the influence of southwest and subtropical monsoons, the GLS, caused by C. zeina, spread into southwest of Yunnan in 2001, and into west of Sichuan by wind and into Hubei maybe by seeds in 2007. In 2013 the disease outbreak in the west of Henan and in 2014 occurred in west of Shaanxi that means C. zeina GLS was colonized in north maize production area. In the future, with the influence of monsoon, C. zeina GLS will spread into southeast of Gansu, south of Ningxia and north of Shaanxi, and will be moved slowly toward the north and east areas which are important production areas of spring maize in China. If the disease reaches the north of China that is the place of C. zeae-maydia GLS occurred at present, C. zeina GLS will be a new destructive disease in the main maize production areas.【Conclusion】It was confirmed that C. zeina was colonized in Guizhou, Sichuan, Shaanxi and Henan as well as C. zeae-maydis in Hebei, Shaanxi and Henan. C. zeina crossed the Bashan and Qinling Mountains into the north spring maize areas and caused severe GLS disease in west of Shaanxi and west of Henan. The main reasons of C. zeina GLS fast spreading were the monsoon action and the seed-borne causal fungus. In the future, C. zeina GLS will be slowly moved to the areas including where the GLS has not occurred yet and C. zeae-maydis GLS spread areas, thus will be a new threat to maize production in China.

Screening and Activity Determination of the Binding Peptide of Vip3Aa10 from Bacillus thuringiensis

DING Zhao-xin, WANG Han-yi, CAO Li-juan, HAO Yan-tong, SHEN Xiao-hong, LIU Jing-guo

Scientia Agricultura Sinica. 2015, 48(18): 3627-3634. doi:10.3864/j.issn.0578-1752.2015.18.006

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【Objective】Vip3A, which is produced and secreted by Bacillus thuringiensis at the vegetative stage, has a wide spectrum of activities against Lepidopteran insects. The receptor of Vip3A toxin on the midgut of sensitive insect has been not identified so far. The phage display technology was used to try to screen the binding peptide of Vip3Aa10 in this article, which may provide a clue for the discovery of the mode of action of Vip3A.【Method】pET28a-Vip3Aa10 plasmid was transformed into E. coli BL21 (DE3) cells, which was induced by IPTG. The expressed Vip3Aa10 was isolated by affinity chromatography, followed by digestion with trypsin and further purification with ion exchange chromatography. The specific binding phages of Vip3A were screened from phage display peptide library with the Vip3Aa10 as bait after four rounds screening with gradual stringent condition. The gene fragment inserted into phage was amplified by PCR with the genomic DNA of screened phage as template, followed by gene sequencing and amino acid deducing. The peptide synthesized by chemistry method was incubated with brush border membrane vesicles (BBMV) together with Vip3Aa10. And the influence of peptide on the interaction of Vip3Aa10 with BBMV was determined by Western blotting. For bioassay, the peptide was loaded with Vip3Aa10 on the surface of artificial diet. After the surface of diet was dry, one first instar Spodoptera exigua larva was placed in each well. Larvae mortality was scored after 6 days. 【Result】E. coli BL21(DE3) containing pET28a-Vip3Aa10 plasmid was induced by IPTG at 25℃. The expressed Vip3Aa10 was soluble, which was isolated by affinity chromatography, activated by trypsin and further purified by ion exchange chromatography, successively. The peptides were isolated through four rounds screening with activated Vip3Aa10 as bait. Nine peptides were screened from Ph.D.-12, including three abundant peptides, which were named P12-1, P12-2 and P12-3, respectively. Five peptides were screened from Ph.D.-7, among which there was one abundant peptide, named P7-1. Binding assay result showed that P12-2 and P7-1 could inhibit the interaction of Vip3Aa10 with BBMV to different extents. Bioassay result showed that P7-1 could significantly reduce the insecticidal activity of Vip3Aa10 against S. exigua. 【Conclusion】The peptide P7-1 could inhibit the interaction between Vip3Aa10 and BBMV significantly, and reduce the insecticidal activity of Vip3Aa10 up to 35%.

Changes in Soil Microbial Biomass and Community Structure with Cultivation Chronosequence of Greenhouse Vegetables

SONG Meng-ya, LI Zhong-pei, WU Meng, LIU Ming, JIANG Chun-yu

Scientia Agricultura Sinica. 2015, 48(18): 3635-3644. doi:10.3864/j.issn.0578-1752.2015.18.007

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【Objective】 This paper mainly studied the changes in soil microbial biomass and community structure with cultivation chronosequence of greenhouse vegetables, and explored the reason and mechanism of soil degradation under highly-intensified land use. The results would provide a scientific basis and practical guidance for soil quality maintenance and sustainable utilization of farmland. 【Method】 In this study, 0-20 cm soils were collected in 3 a, 6 a and 10 a greenhouse vegetable cultivation converted from rice-wheat rotation farmland in Changshu city, Jiangsu Province, with the adjacent rice-wheat rotation farmland as control. Soil nutrients, microbial biomass and microbial community diversity were measured. 【Result】 Soil in 3 a greenhouse vegetable cultivation converted from rice-wheat rotation farmland had rich microbial diversity and high nutrient contents. While soil in 6 a greenhouse vegetable cultivation showed significant acidification and microbial diversity decrease and nutrient accumulation. From 3 a to 10 a greenhouse vegetable cultivation, the available nitrogen increased by 66.1% and the available phosphorus increased by 97.2%. Soil pH in 3 a greenhouse vegetable cultivation was neutral, while that in 6 a cultivation was significantly to be acidic. Soil microbial biomass C and microbial quotient in 3 a greenhouse vegetable cultivation were higher than those in 6 a and 10 a cultivation. BIOLOG analysis showed that AWCD value and microbial diversity index in the soil of 3 a greenhouse vegetable cultivation were the highest among all treatments, which means the maximum absorption and utilization for carbon sources. PLFA analysis showed that soil in 3 a greenhouse vegetable cultivation had highest total PLFA concentrations in microorganisms and bacteria, fungi, actinomycetes, while those in 10 a cultivation significantly decreased by 27.4%, 21.8%, 42.7%, and 49.4% (P＜0.05), respectively. Principal component analysis showed that the diversity of microbial community structure had changed significantly.【Conclusion】The soil microbial properties changed significantly with cultivation years of greenhouse vegetable. In a 3 a of greenhouse vegetable cultivation, high amount of fertilizer application would increase soil microbial biomass and community diversity. In case it extended to 6 a cultivation soil pH and microbial diversity obviously decreased and soil biological quality degraded significantly. The rational application of fertilizer should be emphasized to prevent soil degradation.

Soil Selenium (Se) Status and the Production on Se-Enriched Hulless Barley in the Tibet Autonomous Region

QU Hang, NYIMA Tashi, WEI Ze-xiu, MEI Xu-rong

Scientia Agricultura Sinica. 2015, 48(18): 3645-3653. doi:10.3864/j.issn.0578-1752.2015.18.008

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Tibet is a notably Se-deficient region in that it negatively affects the health among local residents. Hulless or “naked” barley or barley (Hordeum vulgare L. var. nudum Hook. f.), as a stable food, is widely grown in Tibet, and Se-biofortification of hulless barley could be a feasible way to increase dietary Se intake. Moreover, great attention is paid by scientists at home and abroad. However, the study on the effect of Se-biofortification on hulless barley in Tibet has not yet been reported. Status of soil Se, hulless barley production and Se content of hulless barley, and the production pathways on Se-enriched hulless barley in Tibet were discussed. (1) Previous studies identified the total soil Se content and distribution of Tibet. In Tibet, average soil total Se content was (0.150±0.084) mg·kg^-1, which was half of that of China’s soils [(0.290±0.255) mg·kg^-1]. Se-deficient soils were largely distributed in the north of the Yalu Zangbu River of Tibet, and total soil Se content was less than 0.1 mg·kg^-1, while high-Se soils were normally located in the opposite area, and total soil Se content was more than 0.3 mg·kg^-1, such as Gangba County, Tsome County, Lhuntse County, and Tsona County. (2) Although, the planting area and production of hulless barley of Tibet was 1.2×10⁵hm² and 6.2×10⁵ ton, accounted for 21% and 29% of China’s barley planting area and production, the average grain Se content of hulless barley was 0.02 mg·kg^-1, while the average Se content of feedstuff was 0.03 mg·kg^-1, i.e., straw of hulless barley, and the blood Se content of livestock of Tibet was also lower than the critical level. The estimated Se intake through hulless barley consumption was 8 μg? person^-1?d^-1 for Tibetan, while total dietary Se intake (10-16 μg?person^-1?d^-1) was far behind the recommendation, even if the Se intakes by meat, milk, and vegetables were included. (3) Considering the high altitude and complex climate of Tibet, the problems and corresponding solutions, such as optimization of Se fertilizer amount in different production areas, the different response in grain Se content of hulless barley with foliar application and nature soil condition, and planning and utilization of high-Se soils of Tibet were proposed. Se-biofortification could be of benefit to increase the quality of crops and livestock and to improve the health of the Tibetan people.

Characteristics Analysis of Agricultural Nonpoint Source Pollution on Tuojiang River Basin

HU Yun-yun, WANG Yong-dong, LI Ting-xuan, ZHENG Zi-cheng, PU Yong

Scientia Agricultura Sinica. 2015, 48(18): 3654-3665. doi:10.3864/j.issn.0578-1752.2015.18.009

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【Objective】 In order to accurately understand the current status of agricultural non-point source pollution on Tuojiang River Basin and find the main pollution source as well as the key pollutants, the agricultural non-point source pollution emission characteristics of Tuojiang River Basin were analyzed, which would provide a theoretical basis for the prevention or control of river basin pollution. 【Method】The historical data statistical analysis method was adopted to analyze the characteristics of agriculture non-point source pollution for twenty-five counties in 2012. The pollutant emissions were estimated by pollution discharge coefficient method and pollution evaluation and sources analysis were carried out by equivalent pollution load method. 【Result】The absolute discharge amount of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) of agriculture non-point pollution in the studied area were 52.56×10⁴, 4.10×10⁴and 0.55×10⁴t, respectively, in 2012, it is thus obvious that the COD was more than TN and TP. Characteristics of each stream segment were similar to the watershed. Besides, the absolute discharge pollutant of midstream was the most, while the downstream’s was the least. The upstream’s was next only to the midstream’s. The absolute discharge of the pollutants in Renshou county was the highest in the whole basin. At the same time, the absolute discharge of pollutants in Jianyang, Yanjiang and Anyue was also higher than other counties. And the above four counties are also located in midstream. By using standard load evaluation, it was found that the total equivalent pollution load of whole basin was 79 468.23 m³. The equivalent pollution load of TN was the highest (34 151.65 m³), accounting for 42.98% of total emission standard. TP and COD were relatively less. The equivalent pollution load of TP just accounted for 28.98% and the equivalent pollution load of each section on basin also showed TN > TP, COD. In addition, all the counties’ equivalent emission coefficient also presented TN was the highest. The equivalent pollution load almost all come from livestock breeding (44 898.96 m³), accounting for 56.50% of total emission standard. At the same time, livestock breeding as the main source of pollutant, its equivalent pollution load was 56.50% of the total watersheds’. Rural life source’s total equivalent pollution load followed the livestock breeding, while aquaculture source’s was the least (1 311.91 m³). Each stream segment’s equivalent pollution load in the river mainly came from livestock breeding, too. The midstream had the most equivalent pollution load on the Tuojiang River (56 095.43m³). Meanwhile, the equivalent pollution load from upstream and downstream was 12 817.43 and 10 555.37 m³, respectively. Renshou county’s equivalent pollution load was the highest (11 309.51 m³) among the all the counties, which is located in the midstream. Ziliujing county, located in the downstream instead. Refer to the results of equivalent pollution method, twenty-five counties are divided into four types of pollution area. The areas are respectively livestock breeding-rural life leading area, livestock breeding leading area and livestock breeding heavy polluted leading area and rural life leading area. 【Conclusion】 Based on the results above, it was clear that livestock breeding is the key source and the primary pollutant is TN on Tuojiang River watersheds. Tuojiang River Basin agricultural non-point source pollution was combined by production and life. The most seriousiy polluted region is the midstream of Tuojiang, which needs to be most prevented and controlled.

Genetic Analysis and QTL Mapping of Wax Powder on the Surface of Cucumber Fruit

TIAN Gui-li, ZHANG Sheng-ping, SONG Zi-chao, ZHANG Song, CUI Jin-ying, MIAO Han, GU Xing-fang

Scientia Agricultura Sinica. 2015, 48(18): 3666-3675. doi:10.3864/j.issn.0578-1752.2015.18.010

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【Objective】Cucumber (Cucumis sativus L.) is an important world vegetable in the world and its output was over 65 000 million kilos in 2012. For many years, plant breeders have focused their attentions on improving fruit quality, especially in flavor, nutrition, and appearance of cucumber. Several researches on the traits to affecting the appearance quality of cucumber fruit have been reported. However, up to now the amount of wax on the surface of the fruit has received little attention. Wax powder is one of the important fruit appearance quality traits in cucumber. The inheritance and QTL mapping will help to understand the molecular mechanism of wax powder formation, lay a foundation for the fine mapping and gene cloning, and provide a theoretical basis for selecting cucumber lines with little wax powder.【Method】In this study, six generations were developed from the cross between cucumber lines with heavy wax powder ‘PI183697’ and light wax powder ‘1101’ under different environmental conditions of Hainan and Beijing. The amount of wax powder on the fruit surface was measured quantitatively with colour meter (CM-700 d).2-3 cucumbers in each individual and five parts on each cucumber were selected for measurement, and then the calculated average values were used to estimate the inheritance. For the genetic analysis, 1 288 SSR markers were tested and 128 that were found to be polymorphic between ‘PI183697’ and ‘1101’ were used for linkage analysis of F₂ populations. A linkage group was constructed by using JoinMap4.0 with minimum LOD 3.0, and QTL detection for wax powder was conducted with MapQTL4.0.【Result】Genetic analysis showed that the trait of wax powder in ‘PI183697’ was inherited quantitatively. The mixed major gene plus polygene inheritance model of plant quantitative traits was applied to the six generations for genetic analysis. The result showed that the trait of wax powder on cucumber fruit surface was controlled by one additive major gene plus additive-dominant polygene (D-2 model) in the joint analysis of six generations. Linkage maps from two F₂ populations containing seven chromosomes and 128 SSR markers were constructed and seven QTLs relating to wax powder were identified. One QTL locus on Chr.1, Chr.3 and Chr.5, respectively, and four loci on Chr.6 were detected, which were WP1.1, WP3.1, WP5.1, WP6.1, WP6.2, WP6.3 and WP6.4. The QTL loci WP5.1 and WP6.2 were detected in two seasons, having LOD scores of 7.70, 4.81, 4.21, and 6.69, and R²of 14.9%, 12.4%, 8.0% and 16.7%, respectively. 【Conclusion】The inheritance of wax powder is quantitative and controlled by one additive major gene plus additive-dominant polygene (D-2 model). According to QTL mapping, the QTL loci WP5.1 and WP6.2 were repeatedly detected. Thus it was predicted that the major QTL loci may be located on Chr.5 and Chr.6.

Study on the Molecular Mechanism Controlling Differences in Fruit Texture Formation of Apple Soft/Crisp Strains

ZHANG Rui, ZHANG Zong-ying, GAO Li-ping, JI Xiao-hao, MAO Zhi-quan, XU Hai-feng, WANG Nan, WU Shu-jing, CHEN Xue-sen

Scientia Agricultura Sinica. 2015, 48(18): 3676-3688. doi:10.3864/j.issn.0578-1752.2015.18.011

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【Objective】In order to perfect the breeding theory and technology system of functional apple, the molecular mechanism controlling differences in fruit texture formation of soft/crisp strains from the cross progenies of ‘Fuji’ and M. sieversii f. neidzwetzkyana was studied. 【Method】The ethylene production, fruit firmness, crispness, the relative expression intensity of 4 genes related to ethylene biosynthesis (ACS1 etc.) and 30 genes related to fruit softening (PG) were detected in fruits of different development stages of two cross progenies of ‘Fuji’ and M. sieversii f. neidzwetzkyana (‘Hongmian2’ and ‘Hongcui2’). 【Result】Fruit firmness and crispness both declined during development period in both ‘Hongmian2’ and ‘Hongcui2’, but fruit firmness and crispness of ‘Hongcui2’ was significantly higher than that in ‘Hongmian2’ all the time. The ethylene production of ‘Hongmian2’ increased at DAFB 120 d and presented a peak of ethylene production, while the ethylene production of ‘Hongcui2’ didn’t increase significantly at DAFB 120 d and had no obvious peak. The expression patterns of 4 ethylene biosynthesis genes were different. The expression of ACS1, ACO1 and ACO2 in ‘Hongmian2’ during late development period weighed over 94%, while ACS3a showed constitutive expression, occupying 50% of total expression during early and late development period, respectively. The expression periods of 30 genes related to fruit softening were different. With over 70% of the total expression, 15 genes (PL, AF1, EG2 and XET1 etc.) and 5 genes (PG, AF3, XET2, XET10 and XET11) mainly expressed during early development and late development period, respectively. Except 6 genes (PL, AF1 etc.), the expression of other 24 genes (PG etc.) in ‘Hongcui2’ was significantly lower than that in ‘Hongmian2’. 【Conclusion】The appearance of ethylene production peak during late development period and the up-regulated expression of genes related to ethylene biosynthesis and fruit softening during early and late development period resulted in the softening of ‘Hongmian2’ before harvest and the texture difference between ‘Hongmian2’ and ‘Hongcui2’.

Characteristics of Maillard Reaction Products from Enzymatic Hydrolysate of Chicken Bone Extract as Influenced by pH and Temperature

HU Li, WANG Jin-zhi, ZHANG Chun-hui, TANG Chun-hong, DU Gui-hong, LI Xia, LI Chun-hong

Scientia Agricultura Sinica. 2015, 48(18): 3689-3700. doi:10.3864/j.issn.0578-1752.2015.18.012

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【Objective】To obtain the desired flavor quality and antioxidant activity Maillard reaction products (MRPs) from enzymatic hydrolysate of chicken bone extract, the effects of controlled Maillard reaction parameters on those qualities were studied in this paper.【Method】Enzymatic hydrolysate of the chicken bone extract was sequentially added with 0.5% (w/w) xylose, cysteine hydrochloride, and thiamin to adjust pH values at pH 5, pH 7, and pH 9 with 6 mol·L^-1 NaOH, respectively, then reacted for 90 min in the Maillard reaction kettle at 95℃, 105℃, 115℃, respectively. Indicators including UV absorption rate, browning rate, reducing power, ABTS+ radical scavenging activity were measured by UV-visible spectrophotometer. The MW distribution of peptides of different controlled reaction conditions were analyzed by gel permeation chromatography (GPC) with HPLC. Changes of flavor were observed by electronic nose and electronic tongue. The acceptability of MRPs flavor was determined by sensory evaluation. Changes of plasmid DNA damage protective effect of MRPs were analyzed by agarose gel electrophoresis. Correlation analysis between indexes of MRPs was also performed to establish possible linkages between controlled reaction condition and different parameters of MRPs in this study.【Result】The content of intermediate product increased with pH value. The higher the pH value was, the faster the primary reaction rate of Maillard was, while the degree of browning increased with temperature rose. The content of peptides of 1 000-200 Da in all the reaction systems accounted for more than 50% of the total peptides content, and was significantly correlated with sensory evaluation score (r=0.772, P<0.05). The contents of peptides of >3 000 Da, 3 000-1 000 Da, and <200 Da were highly positive correlated with each other (P<0.01), and were all highly negatively correlated with the peptides of 1 000-200 Da (P<0.01). Principal component analysis (PCA) on the flavor of each MRPs indicated that the temperature could significantly change the composition of volatile flavor of MRPs, while different pH value mainly caused the differences in taste of MRPs. Sensory evaluation score of each MRPs decreased with the increasing of pH, the score of the MRPs which prepared at pH 5 and 105℃ increased by 57.32% compared to the initial sample, and was the highest. Reducing power and ABTS+ scavenging capacity of the MRPs with pH 5 were significantly higher than that of pH 7 and 9, while DNA damage protection effect of MRPs was significantly positively correlated with ABTS + scavenging capacity (r=0.689, P<0.05). Correlation analysis results showed that sensory evaluation scorewas highly negatively correlated with UV absorption rate, browning rate and content of peptides with MW <200 Da (P<0.01), while UV absorption rate was highly negatively correlated with reducing power (P<0.01). 【Conclusion】In the Maillard reaction system of enzymatic hydrolysate of chicken bone extract, pH and the reaction temperature significantly affect the quality characteristics of MRPs. In the range of this experiment, MRPs with controlled reaction conditions of pH 5 and 105^oC was better than the other groups on the flavor quality, color and comprehensive antioxidant activities.

Study on the Effect of Lipopolysaccharide on Hepatic Metabolism in Dairy Goat Liver

WANG Lin-feng, JIA Shao-dan, YANG Gai-qing, ZHU He-shui, LIU Ru-yi, YAN Ping, LI Ming, YANG Guo-yu

Scientia Agricultura Sinica. 2015, 48(18): 3701-3710. doi:10.3864/j.issn.0578-1752.2015.18.013

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【Objective】 The objective of this experiment is to study the effect of lipopolysaccharide (LPS) on metabolism of dairy goat liver, explore the characteristic metabolites in the liver and clarify the mechanism of hepatic dysbolism caused by LPS.【Method】Total 15 Guanzhong dairy goats of 12-month-old with 24-28 kg live body weight (BW) were selected and divided into three groups randomly, i.e. control group (CTL, goat No. 1-5), LPS-L group (LPS-L, goat No. 6-10) and LPS-H group (LPS-H, goat No.11-15). Animals were fed total mixed ration (TMR) made according to NRC (2007). The experimental goats were fed with feeds and water ad libitum. After 14d adaption, the experiment was conducted. At the beginning of the experiment (0 h), the goats in LPS-L and LPS-H were given 20 and 40μg·kg^-1 BW of LPS solution via intraperitoneal injections, respectively. The goats in CTL were received same volume of saline water. 24 h later, goats in each LPS treatment groups were added LPS solution once again. 48 h later from the beginning, blood samples were drawn from jugular vein and were centrifuged to extract plasma for biochemical determination. Subsequently, the goats’ liver tissue samples were collected by biopsy and marked and stored in liquid nitrogen. ¹H-NMR metabonomics was used to research the changes of metabolites in goat liver, the obtained metabolites. The data variables (concentration value of metabolites) were analyzed by the software of partial least squares discriminant analysis (PLS-DA) installed in the equipment to identify metabolic differences between the groups of each treatment. 【Result】Serum biochemical results showed that the concentration of ALT, AST and TBIL increased significantly, while TG, TC, VLDL, NEFA, HDL, LDL, ALB, TP decreased to different degrees in LPS treated groups compared with that of CTL, indicating the goats liver were injured to some degrees and the dysbolism was occurred in goat liver. With the ¹H-NMR metabonomics determination, totally 69 metabolites were detectedbased on its identification database of Chenomx. After the metabolite variables analyzing using PLS-DA, it showed that the CTL, LPS-L and LPS-H groups could be clustered and distinguished based on the metabolomic data analysis. Nine out of 69 metabolites differed significantly among the three groups. Based on the statistics and analysis between any two of the groups, 6 metabolites located in LPS-L and LPS-H groups were notable compared with the CTL, and 3 metabolites were different significantly between LPS-L and LPS-H. Further analysis indicated that these metabolites were related to amino acid metabolism, fat metabolism and carbohydrate metabolism in the liver.【Conclusion】In conclusion, LPS induced significant changes in liver reflected in blood biochemical indices. Metabolomics profile could precisely detect characteristic metabolites and effectively distinguish LPS-L and LPS-H from CTL effectively. Metabolomic technology could clarify the mechanism for liver dysbolism suffering from LPS and provide enough information to diagnose liver injury via analyzing the relevant pathway.

cDNA Cloning and Expression of MITF Gene and Its Effect on Melanin Deposition in Silky Fowl

ZHENG Nen-zhu, XIN Qing-wu, ZHU Zhi-ming, MIAO Zhong-wei, Li Li, Liu Feng-hui, HUANG Qin-lou

Scientia Agricultura Sinica. 2015, 48(18): 3711-3718. doi:10.3864/j.issn.0578-1752.2015.18.014

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【Objective】The aim of this paper was to clone microphthalmia-associaated transcription factor(MITF) , explore its expression and relationship with melanin deposition in different tissues of Silky Fowl, for further studying molecular mechanism of melanin deposition among Silky Fowl.【Method】A total of 150 day-old healthy Silky Fowls were selected as the research materials in this experiments. Degenerate primers and Nested PCR were used to isolate MITFgene from the skin of Silky Fowl, and DNAStar, Clustal X, BioEdit and MEGA4.0 software were adopted to analyze biological information of the obtained sequence. Quantitative real-time PCR (qRT-PCR) and ultraviolet spectrophotometry (US) were employed, respectively, to study MITF expression characteristics and melanin deposition in tissues of Silky Fowl, and linear regression estimation was applied to identify the correlation between MITF gene expression and melanin deposition in the tissues of Silky Fowl.【Result】Results showed that the 1 431 bp cDNA sequence of MITF gene was obtained by sequencing and splicing, which contained a complete CDS (25-1 431bp). The CDS domain was composed by 468 amino acids (GenBank accession No. KC879241) with a predicted molecular weight of 52.42kD , an isoelectric point of 6.47, and a conserved basic-helix-loop-helix leucine-zipper (bHLH-zip) protein structure.The homology comparison indicated that the Silky MITF gene shared 100% amino acid homology to Gallus gallus, above 98% to other birds，and about 90% to mammal in CDS domaim. The amino acid phylogenetic tree analysis demonstrated that Silky Fowl MITF had the closest genetic relationship to Gallus gallus, but the farthest to pig and human. The qRT-PCR confirmed that different expressions of MITF gene were detected among tissues of Silky Fowl (P＜0.01), with the highest expression in the skin which was about 2.9 times that of the kidney, 4.4 times that of the gizzard, 11.4 times that of the liver, and 86.2 times that of the muscle. The ultraviolet spectrophotmeter examination showed that the law of melanin depositionwas consistent with thatof MITF expression in tissues, with an overall trend: skin＞kidney＞gizzard ＞liver＞muscular. Correlation analysis diplayed that there was a positive correlation between MITF expression and melanin deposition(P＜0.05).【Conclusion】 MITF gene is highly conservative in the evolution of animal species, the gene expression is specific in tissues, and plays a positive role in the regulation of melanin deposition on Silky Fowl, whose high expression may contribute to the formation of melanin.

Reflections on Establishing a Long-Term Mechanism of Grassland Ecological Compensation in China

WEI Qi, HOU Xiang-yang

Scientia Agricultura Sinica. 2015, 48(18): 3719-3726. doi:10.3864/j.issn.0578-1752.2015.18.015

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Ecological compensation is an important environmental economic policy for ecological environment protection, ecological civilization construction and ecological resources sustainable development. How to establish an equitable and efficient long-term mechanism of ecological compensation is a challenging long-term research issue in the theory and practice of ecological compensation at home and abroad, which is related to some key problems, including direction and focus of compensation policy, the effect and efficiency of policy implementation, ecological civilization construction and sustainable development. Extensive grasslands are important for producing livestock base, biodiversity conservation center, ecological safety shelter zone and food safety grounding. The grassland ecological compensation has been preliminarily established, both investment scale and coverage are larger, and obtained significant achievements, but the grassland ecological environment situation that the partial better and in whole worse has still no fundamental change. Therefore, discussing and establishing the ecological compensation mechanism, combining fairness with long-term efficiency, which is a vital measure for the coordination of multiple functions of grassland resources to achieve “win-win” outcomes for production, life and ecosystems, to ensure the sustainability of ecological resource protection and utilization. The study summarized the concept and theory of ecological compensation, the development trend of long-term mechanisms at home and abroad, demonstrated establishing the long-term mechanism of ecological compensation was very important for ecological environment protection and famers become rich. Based on field investigate on different grassland regional implementations of grasslands ecological compensation and analyzed the Herders’ production decision inherent behavior on grassland ecological compensation effects and the current implementation effects, the study considered the major challenges to grassland ecological compensation in China as follows: long-term debt leads to grassland ecological management so difficult. The grassland ecological investments are less and cycle shorter so that is difficult to effectively consolidate protection results. Herders have desirable stocking rate and inertia overstocking which affects livestock reduction for ecological compensation. The study proposes to further establish the policy suggestion for long-term mechanism of ecological compensation in accordance with the national situation of China, the main suggestions include as follows: elongate the period of ecological compensation policy, increase the award fund, implement diversified adaptive livestock reduction model, develop the grassland ecological animal husbandry management pattern and strengthen the institutional guarantee system of grassland animal husbandry. Objectives were to provide a theoretical basis and practical support for the scientific protection of fragile ecological resources, sustainable exploitation and utilization of grassland resources and ecological civilization construction in China.

The Influence of Whole-Genome Triplication (WGT) on the Candidate Genes of Pollen Specific Expression in Brassica rapa

WANG Xiao-bo, MA Yuan, CHENG Feng, WU Jian, LIANG Jian-li, WANG Xiao-wu

Scientia Agricultura Sinica. 2015, 48(18): 3727-3732. doi:10.3864/j.issn.0578-1752.2015.18.016

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【Objective】 The objective of this study is to research the evolution of the candidate genes of pollen specific expression in Brassica rapa after whole-genome triplication (WGT). This study will provide a theoretical basis for pollen specific expressed genes in B. rapa in the future research. 【Method】 The genes of pollen specific expression in B. rapa were acquired by SynOrths referred to Arabidopsis thaliana based on their syntenic relationship. InterproScan was used to get their Gene Ontology (GO), which were grouped into 13 categories related to pollen. To compare among three duplicated categories, the ratio of gene number of each GO to total number of genes in these categories was counted. Furthermore, these genes were grouped into three subgenomes based on their explicit dataset of B. rapa genes. Based on the syntenic relationship of tandem genes of pollen specific expression in B. rapa with genes in A. thaliana，whether these genes were generated before WGT or after the event was determined. 【Result】 Totally, 1962 candidate genes of pollen specific expression in B. rapa were verified via the syntenic relationship with 1651 genes in A. thaliana. There are 182 tandem genes in A. thaliana, while 137 tandem genes in B. rapa. The result showed that the number of pollen specific expressed genes between A. thaliana and B. rapa was almost equivalent, so it could be inferred that most of copy genes of B. rapa were lost after WGT event occurs. A total of 549 genes of pollen specific expression in A. thaliana were not found syntenic counterparts in B. rapa, so these genes might be also lost after WGT. There are 898 genes of pollen specific expression in A. thaliana corresponding to these genes with single-copy, double-copies or triple-copies in B. rapa. A total of 480 genes in A. thaliana with single-copy in B. rapa, accounting for 53.5%, which is the largest proportion. While 322 genes with double-copies account for about 35.8%, and only 96 genes with triple-copies account for 10.7%. The candidate genes of pollen specific expression with triple-copies in all three subgenomes of B. rapa were more than the other two copy classifies on seven functional categories, while the function of these genes with double-copies were dispersed into all functional categories. Most of tandem genes of pollen specific expression were turned into non-tandem genes, but some non-tandem genes of pollen specific expression developed into tandem genes in B. rapa after WGT. 【Conclusion】 These results indicated that the candidate genes of pollen specific expression had an ongoing evolution after WGT, and the WGT event may contribute to the functional difference existed in three classifies of copy genes in B. rapa.

Effect of Rhizosphere Oxygen on the Growth Characteristics of Rice and Its Nitrogen Metabolism at Tillering Stage

ZHAO Xia, XU Chun-mei, WANG Dan-ying, CHEN Song, TAO Long-xing, ZHANG Xiu-fu

Scientia Agricultura Sinica. 2015, 48(18): 3733-3742. doi:10.3864/j.issn.0578-1752.2015.18.017

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【Objective】 The objective of this paper is to study the effect of rhizosphere oxygen content on rice growth characteristics and nitrogen metabolism, and the suitable concentration of rhizosphere oxygen for the growth and nitrogen metabolism of rice at tillering stage. The results of this experiment will be helpful to know the law of oxygen demand and the role of oxygen on rice growth, and provide the reference and a theoretical basis for modification of cold waterlogged paddy field and further improvement of rice yield and nitrogen use efficiency.【Method】The formal experiment was conducted at China National Rice Research Institute in 2013. Two conventional cultivars Zhongjiazao17 and Xiushui134 were grown in hydroponic condition at the space of 15 cm×15 cm with dicyandiamide to keep NH₄⁺:NO₃^-=1:1 in nutrition solution. At ten days after transplanting, the oxygenated devices were installed to control the oxygen concentration in the nutrient solution, and three oxygen treatments were set in this experiment for fifteen days: CK(0.3-2.5 mg·L^-1）, moderate oxygen (MO: 2.3-5.5 mg·L^-1) and high oxygen (HO: 6.5-8.0 mg·L^-1). The portable dissolved oxygen meters（YSI550A, American）was used to examine the oxygen concentration in the nutrient solution【Result】The highest dry matter weight of root, stem and leaf as well as the accumulation of nitrogen were observed in MO treatment, followed by HO treatment and CK in both cultivars. The significant differences between MO treatment and CK were found. The leaf area index, root number, root absorbing area, nitrogen utilization efficiency and tiller numbers of rice in MO treatment were significantly higher than those in HO treatment and CK. The longest root of the two aeration treatments (MO and HO) was markedly higher than CK. The results in this experiment also indicated that Zhonjiazao 17 was more sensitive to oxygen in solution than Xiushui-134, since higher increase in dry matter weight of root, stem and leaf as well as nitrogen accumulation of Zhonjiazao 17 in MO treatment were examined than those of HO treatment compared with CK, whereas there were no significant differences in dry matter weight and nitrogen accumulation of Xiushui 134 between the MO and HO treatments. The variation tendency of the activity of the two key enzymes glutamine synthetase and nitrate reductase in nitrogen metabolism were different between leaves and root, but the difference among the treatments was same in two cultivars. The highest photosynthetic nitrogen use efficiency in MO treatment was observed. 【Conclusion】The fast growth potential is established with the significant promotion of the appropriate oxygen concentration in the nutrient solution on tillering number, formation of leaf area, light capture and root growth, whilst the photosynthetic nitrogen use efficiency is enhanced. However, the promotion of aeration on rice growth reduced in high oxygen concentration. At same time there are different responses among the varieties. The suitable oxygen concentration for rice growth and nitrogen use efficiency is around 2.3-5.5 mg·L^-1.

Evaluation of Drought Resistance and Cold Resistance and Research of Their Relationship at Seedling Stage of Winter Rapeseed (Brassica campestris L.) in Cold and Arid Regions in North China

LIU Hai-qing, SUN Wan-cang, LIU Zi-gang, WU Jun-yan, QIAN Wu, WANG Zhi-jiang, GUO Ren-di, MA Li, HOU Xian-fei, LIU Lin-bo

Scientia Agricultura Sinica. 2015, 48(18): 3743-3756. doi:10.3864/j.issn.0578-1752.2015.18.018

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【Objective】An experiment was conducted to study the cold and drought resistance and its relationship of winter rapeseed. The aim of this study was to provide valuable methods and theories for improvement and overall evaluation of cold and drought resistance of winter rapeseed in north China.【Method】Six rapeseed varieties which have different cold resistance abilities were used to simulate low temperature and drought stress which were implemented by natural drop in temperature (15℃--5℃) and manual water control (days of drought stress were 4 d, 7 d, and 10 d). Changes in morphology, physiology, biochemistry and growth of the winter rapeseed were analyzed. Subordinate function coefficients, fuzzy clustering, correlation analysis and principal component analysis were used to evaluate the cold and drought tolerance comprehensively.【Result】The results showed that the over wintering rate of the 6 different winter rapeseed varieties varied from 20.1% to 94.7%. Morphological characteristics of botany of the rapeseed variety with stronger cold-resistance level was prostrate at seedling stage, the growing point was sagging and below the surface, the leaves color presented dark green and bristles much-ness. The physiological and biochemical indexes changed significantly after cold stress, relative conductivity and content of MDA increased under cold stress, and the increase rate of which became slow with the increase of levels of cold-resistance. But the activities of SOD, POD, CAT and content of SP, SS, Pro were overall ascendant, the variation trend of which became larger with the increase of level of cold-resistance. Under drought stress, the relative conductivity and the content of MDA increased, and the content of chlorophyll and leaf relative water and the ratio of bond water and free water decreased, the length of seedling, fresh and dry weight of leaves and roots decreased. They have a strong capacity of soil water retention, and the wilting coefficient was small, and the rate of range became slow with the strong level of drought-resistance of winter rapeseed varieties. The order of cold-resistance levels of the six winter rapeseed varieties is Longyou 7＞ Longyou 6＞Longyou 9＞Yanyou 2＞Tianyou 2＞Vision, and the drought-resistance levels of the six winter rapeseed varieties is Longyou 6＞Longyou 7＞Longyou 9＞Yanyou 2＞Vision＞Tianyou 2 by integrated evaluation of the main components .【Conclusion】In north China, cold and dry exist side by side and different varieties have significant different abilities of cold and drought resistance, which resulted in cross adaptation of winter rapeseed, so the winter rapeseed varieties with strong cold resistance planted in north China also have strong drought resistance.

Effects of Single-Seed Precision Sowing on Population Structure and Yield of Peanuts with Super-High Yield Cultivation

ZHANG Jia-lei, GUO Feng, YANG Dian-qing, MENG Jing-jing, YANG Sha, WANG Xing-yu, TAO Shou-xiang, LI Xin-guo, WAN Shu-bo

Scientia Agricultura Sinica. 2015, 48(18): 3757-3766. doi:10.3864/j.issn.0578-1752.2015.18.019

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【Objective】While the population quality declined and the yield decreased of double-seed sowing peanuts in a super-high yield condition, single-seed planting can alleviate the contradiction between population and individuals, to realize a high yield of peanuts. Research was conducted on the effects on peanut ontogeny and population structure under single-seed planting, to explore the ideal plant type and super-high yield peanut reasonable group construction, to further increase the latent capacity of high-yield.【Method】 In 2014, four parcels of super high yield experimental fields of spring peanuts were established in Pingdu, Junan, Guanxian, and Ningyang, respectively. Peanut cultivar Huayu 22 was used as materials to study the differences between single-seed sowing (SS) and double-seed sowing (DS) modes on individual development, population structure, and yield. The investigation of plant trait was conducted on anthesis, pod-setting, pod-filling and maturity period in different trial locations, respectively. At maturity period, the investigation was further conducted on the number of the pod, young pod, immature pod, full pod, tow kernel pod and economic coefficient, respectively. When harvested, experts were organized to conduct on predict yield with specific area.【Result】The pod yield of SS peanuts at each test point was significantly higher than that of DS peanuts, and the average increased by 13.92%. The increase was mainly due to the increase of the pod numbers per plant, the group pod number per hectare (except inunmature ones) was up to 5925 000. Simutaneously, the main stem height, lateral branch length, node number of main stem, leaf number of main stem, branch number, root-shoot ratio, and leaf area index of SS peanuts were significantly higher than those of DS peanuts at the early growing stage, these helped SS peanuts to seal the ridge earlier and increased the effective photosynthetic area. More leaves on the main stem of SS peanuts than those of DS peanuts at the maturity stage prolonged the effective photosynthetic time. The pod yield of Junan was significantly higher than that of other three test points. For all the tests, the pod weight per plant had a negative correlation with main stem height and lateral branch length, but a significant positive correlation with branch number and leaf area index at the pod-filling stage under single-seed sowing. As the highest test point, in Junan, the pod weight per plant was significantly positively correlated with leaf area index and economic coefficient at the maturity stage under single-seed sowing.【Conclusion】In this case, the results indicated that the peanut above-ground plant was redundant under the condition of super high yield. The branch number of SS peanuts was an important factor affecting the pod weight, and the key factor to further improve the yield was to increase the pod number and economic coefficient.

Competition and Coexistence of Alfalfa (Medicago sativa L.) and Smooth Brome (Bromus inermis Layss.) in Mixture

XIE Kai-yun, ZHANG Ying-jun, LI Xiang-lin, HE Feng, WAN Li-qiang, WANG Dong, QIN Yan

Scientia Agricultura Sinica. 2015, 48(18): 3767-3778. doi:10.3864/j.issn.0578-1752.2015.18.020

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【Objective】 The relationship between intraspecific competition and interspecific competition simultaneously exists in mixture of legume and grass, the results of the competition led to the phenomenon that one species will be fade, the other will be a dominant gradually due to difference of the competitiveness of different plants. It is of great significance to study the mechanism of competition and coexistence between legume and grass to maintain stable and high yield in mixture grassland. 【Method】A pot experiment was conducted to examine the effects of variable rates of nitrogen application (0, 75, 150 kg N·hm^-2), hereafter referred as N0, N75, N150, on competition of alfalfa (Medicago sativa L.), Smooth brome (Bromus inermis Layss.) in monoculture, alfalfa and smooth brome in mixture (1:1), with indicators including the relative biomass (RY), relative density (RD), competitive ratio (CR), relative yield total (RYT), percentage of atmospheric N₂ fixation (%Ndfa) and percentage of N transferred (%N Trans), to study the mechanism of competition and coexistence in mixcure of smooth brome and alfalfa. 【Result】 The results showed that with increasing of N application (from 0 to 150 kg·hm^-2), the above-ground and below-ground biomass and tiller number of smooth brome significantly increased (P＜0.05), and there was no significant difference in the above-ground and below-ground biomass and branch number of alfalfa there was no significant in monoculture (P＞0.05). The above-ground and below-ground biomass and tiller number of smooth brome increased, which in a certain extent inhibited biomass and branch number of alfalfa in mixture (P＜0.05). The ability of smooth brome expand above-ground space by means of increase its tiller number was stronger than that of alfalfa in mixture. The above-ground and below-ground biomass and tiller number of individual smooth brome were significantly higher in mixcure than in monoculture regardless of N application (P＜0.05), but that of alfalfa were the opposite (P＜0.05). The competitive ratio of smooth brome in mixture was always greater than 1.0 while the competitive rate of alfalfa was always less than 1.0, which means that the competitiveness of smooth brome was stronger than that of alfalfa, and in the whole growth period, the competitiveness of smooth brome would gradually weak, and the competitiveness of alfalfa increased. At second, third and fourth sampling in the N0 treatment, the relative yield total (RYT) of smooth brome and alfalfa in mixture was significantly greater than 1.0 (P＜0.05), which means that there was no obvious effect of competition between smooth brome and alfalfa, and it was mainly attributed to the biological nitrogen fixation of alfalfa's contribution to smooth brome. RYT of smooth brome and alfalfa in mixture showed no significant differences with 1.0 in N75 and N150 treatments(P＞0.05). In addition, application of N fertilizer significantly inhibited the proportion of N₂ fixation of alfalfa and N transfer from smooth to alfalfa, forcing alfalfa compete for soil N and fertilizer N with smooth brome. 【Conclusion】 Applied N fertilizer at 75 and 150 kg N·hm^-2 enhanced the competitiveness of smooth brome, and inhibited the proportion of biological nitrogen fixation of alfalfa and nitrogen transfer form alfalfa to smooth brome, diminished the promotion effect and enhanced competition effect of the two.

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