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2017 Vol. 16 No. 07 Previous Issue    Next Issue

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Crop Science
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Crop Science

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Genetic mapping of quantitative trait loci for the stigma exsertion rate in rice (Oryza sativa L.) Md Habibur Rahman, ZHANG Ying-xin, SUN Lian-ping, ZHANG Ke-qin, Md Sazzadur Rahman, WU Wei-xun, ZHAN Xiao-deng, CAO Li-yong, CHENG Shi-hua 2017, 16(07): 1423-1431.  DOI: 10.1016/S2095-3119(16)61540-X Abstract ( )   PDF in ScienceDirect       The efficiency of hybrid rice seed production can be improved by increasing the percentage of exserted stigmas. To identify quantitative trait loci (QTLs) for this trait, we conducted QTL mapping using 75 chromosome segment substitution lines (CSSLs) developed from a cross between the donor parent, Xieqingzao B (XQZB), a maintainer line which has high stigma exsertion and the recurrent parent, Zhonghui 9308 (ZH9308), a restorer line which has low stigma exsertion. A total of nine QTLs (qSSE5, qSSE10, qSSE11, qDSE10, qDSE11, qTSE5, qTSE6, qTSE10, and qTSE11) for single stigma exsertion (SSE), dual stigma exsertion (DSE) and total stigma exsertion (TSE) were assessed in two environments (Hainan and Zhejiang). Six of these QTLs (qSSE10, qSSE11, qDSE10, qDSE11, qTSE10, and qTSE11) were found in both environments, while one QTL (qTSE6) was found in only Hainan, and two QTLs (qSSE5 and qTSE5) were found in only Zhejiang. The qSSE10, qSSE11, qDSE10, qDSE11, qTSE6, qTSE10, and qTSE11 alleles, which are derived from the parent XQZB, exhibited a positive additive effect. In contrast, the qSSE5 and qTSE5 alleles, which are derived from the parent ZH9308, exhibited a negative additive effect. The SSE, DSE and TSE traits were significantly correlated with each other in an environmentally dependent manner. These results indicated that the lines showing higher values for SSE were more likely to exhibit increased values for DSE, which would ultimately increase TSE. To evaluate the advantage of exserted stigmas for cross-pollination, single, dual and total stigma exsertion should be considered separately in future attempts at genetic improvement to achieve increased production of rice hybrid seeds. This study also provides information for fine mapping, gene cloning and particularly marker-assisted selection (MAS), on the latter and with an emphasis the phenotypic effects and implications of the QTLs for practical use in hybrid rice breeding.

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Dissection of the genetic architecture for tassel branch number by QTL analysis in two related populations in maize CHEN Zheng-jie, YANG Cong, TANG Deng-guo, ZHANG Lei, ZHANG Ling, QU Jing-tao, LIU Jian 2017, 16(07): 1432-1442.  DOI: 10.1016/S2095-3119(16)61538-1 Abstract ( )   PDF in ScienceDirect       Tassel branch number (TBN) is the principal component of maize tassel inflorescence architecture and is a typical quantitative trait controlled by multiple genes. The main objective of this research was to detect quantitative trait loci (QTLs) for TBN. The maize inbred line SICAU1212 was used as the common parent to develop BC1S1 and recombinant inbred line (RIL) populations with inbred lines 3237 and B73, respectively. The two related populations consisted of 123 and 238 lines, respectively. Each population was grown and phenotyped for TBN in two environments. Eleven QTLs were detected in the BC1S1 population, located on chromosomes 2, 3, 5, and 7, accounted for 4.45–26.58% of the phenotypic variation. Two QTLs (qB11Jtbn2-1, qB12Ctbn2-1, qBJtbn2-1; q11JBtbn5-1, qB12Ctbn5-1, qBJtbn5-1) that accounted for more than 10% of the phenotypic variation were identified. Three QTLs located on chromosomes 2, 3 and 5, exhibited stable expression in the two environments. Ten QTLs were detected in the RIL population, located on chromosomes 2, 3, 5, 8, and 10, accounted for 2.69–13.58% of the TBN variation. One QTL (qR14Dtbn2-2) explained >10% of the phenotypic variation. One common QTL (qB12Ctbn2-2, qR14Dtbn2-2, qRJtbn2-2) was detected between the two related populations. Three pairs of epistatic effects were identified between two loci with or without additive effects and accounted for 1.19–4.26% of the phenotypic variance. These results demonstrated that TBN variation was mainly caused by major effects, minor effects and slightly modified by epistatic effects. Thus, identification of QTL for TBN may help elucidate the genetic basis of TBN and also facilitate map-based cloning and marker-assisted selection (MAS) in maize breeding programs.

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Isolation and expression analysis of NtCHS6, a new chalcone synthase gene from Nicotiana tabacum CHEN Shuai, ZHANG Yin-chao, PAN Xu-hao, LI Yi-ting, CUI Li-jie, WU Feng-yan, CAO Mo-ju, YANG Ai-guo , PAN Guang-tang 2017, 16(07): 1443-1450.  DOI: 10.1016/S2095-3119(16)61503-4 Abstract ( )   PDF in ScienceDirect   Chalcone synthases (CHS, EC 2.3.1.74) are key enzymes that catalyze the first committed step in flavonoid biosynthesis. In this study, we isolated a chalcone synthase, named NtCHS6, from Nicotiana tabacum.  This synthase shared high homology with the NSCHSL (Y14507) gene and contained most of the conserved active sites that are in CHS proteins.  The phylogenetic analysis suggested that NtCHS6 protein shared a large genetic distance with other Solanaceae CHS proteins and was the most closely-related to an uncharacterized CHS from Solanum lycopersicum.  The expression analysis indicated that NtCHS6 was abundantly expressed in leaves, especially in mature leaves.  By scrutinizing its upstream promoter sequences, multiple cis-regulatory elements involved in light and drought responsive were detected.  Furthermore, NtCHS6 expression decreased significantly under dark treatment and increased significantly under drought stress.  Our results suggested that NtCHS6 expression exhibited both light responsiveness and drought responsiveness, and might play important roles in ultraviolet protection and drought tolerance.

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Comparison of yield traits in rice among three mechanized planting methods in a rice-wheat rotation system XING Zhi-peng, HU Ya-jie, QIAN Hai-jun, CAO Wei-wei, GUO Bao-wei, WEI Hai-yan, XU Ke, HUO Zhong-yang, ZHOU Gui-sheng, DAI Qi-gen, ZHANG Hong-cheng 2017, 16(07): 1451-1466.  DOI: 10.1016/S2095-3119(16)61562-9 Abstract ( )   PDF in ScienceDirect        Understanding the differences in yield traits of rice among pothole seedling of mechanical transplanting (PSMT), carpet seedling of mechanical transplanting (CSMT) and mechanical direct seeding (MDS) is of great importance not only for rice scientists but also for rice farmers to develop a high-yield production system under mechanical conditions in a rice-wheat rotation system.  However, such traits are yet to be studied among rice varieties of japonica-indica hybrid rice (JIHR), japonica conventional rice (JCR) and indica hybrid rice (IHR).  Field experiments were conducted in 2014 and 2015, where six cultivars of the three rice types JIHR, JCR and IHR were grown individually with PSMT, CSMT and MDS methods, under respective managements for each method to achieve the maximum attainable yield.  Results showed that (i) the PSMT significantly increased grain yield of JIHR by 22.0 and 7.1%, of JCR by 15.6 and 3.7% and of IHR by 22.5 and 7.4%, compared to MDS and CSMT on average across the two years, respectively.  The highest yield was produced by the combination of JIHR and PSMT; (ii) high yield under PSMT was mainly attributed to large sink capacity and high-efficient dry matter accumulation.  With sufficient panicles per hectare, the increase of spikelet number per panicle, especially the increase in spikelet number of the secondary rachis-branches was determined to be the optimal approach for developing a large sink capacity for rice under PSMT.  The optimal tillers development, large leaf area index at heading stage, and high leaf area duration, crop growth rate and net assimilation rate during grain-filling phase could be the cause of sufficient dry matter accumulation for rice under PSMT; (iii) moreover, the PSMT favored plant growth as well as enriched the stems plus sheaths during grain-filling phase, as compared with CSMT and MDS.  These results suggest that PSMT may be an alternative approach to increasing grain yield in a rice-wheat rotation system in the lower reaches of the Yangtze River in China.

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Erect panicle super rice varieties enhance yield by harvest index advantages in high nitrogen and density conditions TANG Liang, GAO Hong, Hirooka Yoshihiro, Homma Koki, Nakazaki Tetsuya, LIU Tian-sheng, Shiraiwa Tatsuhiko, XU Zheng-jin 2017, 16(07): 1467-1473.  DOI: 10.1016/S2095-3119(17)61667-8 Abstract ( )   PDF in ScienceDirect      The erect panicle (Ep) type is an important characteristic for japonica super rice in Northeast China and plays a significant role in enhancing yield. The Ep type is considered to be a genetic ideotype resource to the japonica super rice group by virtue of its agronomic advantages such as grain number per panicle and biomass. This study addresses the effects of nitrogen and planting density conditions on yielding performance regarding panicle type (PT) using the recombinant inbred line (RIL) population derived from the cross between an Ep variety Liaogeng 5 and non-Ep variety Wanlun 422. The genetics underlying the Ep type proved to be robust not only for panicle-type optimization but also plant height, panicle length, flag leaf length and seed density. We also found that regardless of nitrogen and density, correlation between harvest index (HI) and plant height was not significant in Ep type whatever the nitrogen and density. The application of Ep type provides a potential strategy for yield improvement by increasing biomass through HI maintainable in rice.

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Estimating light interception using the color attributes of digital images of cotton canopies XUE Hui-yun, HAN Ying-chun, LI Ya-bing, WANG Guo-ping, FENG Lu, FAN Zheng-yi, DU Wen-li, YANG Bei-fang, MAO Shu-chun 2017, 16(07): 1474-1485.  DOI: 10.1016/S2095-3119(16)61542-3 Abstract ( )   PDF in ScienceDirect       Crop growth and yield depend on canopy light interception (LI). To identify a low-cost and relatively efficient index for measuring LI, several color attributes of red-green-blue (RGB), hue-saturation-intensity (HSI), hue-saturation-value (HSV) color models and the component values of color attributes in the RGB color model were investigated using digital images at six cotton plant population densities in 2012–2014. The results showed that the LI values followed downward quadratic curves after planting. The red (R), green (G) and blue (B) values varied greatly over the years, in accordance with Cai’s research demonstrating that the RGB model is affected by outside light. Quadratic curves were fit to these color attributes at six plant population densities. Additionally, linear regressions of LI on every color attribute revealed that the hue (H) values in HSI and HSV were significantly linearly correlated with LI with a determination coefficient (R2)≥0.89 and a root mean square error (RMSE)=0.05. Thus, the H values in the HSI and HSV models could be used to measure LI, and this hypothesis was validated. The H values are new indexes for quantitatively estimating the LI of heterogeneous crop canopies, which will provide a theoretical basis for optimizing the crop canopy structure. However, further research should be conducted in other crops and under other growing and environmental conditions to verify this finding.

Horticulture

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Genome-wide identification, characterization, and expression analysis of the SWEET gene family in cucumber HU Li-ping, ZHANG Feng, SONG Shu-hui, TANG Xiao-wei, XU Hui, LIU Guang-min, WANG Ya-qin, HE Hong-ju 2017, 16(07): 1486-1501.  DOI: 10.1016/S2095-3119(16)61501-0 Abstract ( )   PDF in ScienceDirect       SWEETs (sugars will eventually be exported transporters) are a novel class of recently identified sugar transporters that play important roles in diverse physiological processes. However, only a few species of the plant SWEET gene family have been functionally identified. Up till now, there has been no systematic analysis of the SWEET gene family in Cucurbitaceae crops. Here, a genome-wide characterization of this family was conducted in cucumber (Cucumis sativus L.). A total of 17 CsSWEET genes were identified, which are not evenly distributed over the seven cucumber chromosomes. Cucumber SWEET protein sequences possess seven conserved domains and two putative serine phosphorylation sites. The phylogenetic tree of the SWEET genes in cucumber, Arabidopsis thaliana, and Oryza sativa was constructed, and all the SWEET genes were divided into four clades. In addition, a number of putative cis-elements were identified in the promoter regions of these CsSWEET genes: nine types involved in phytohormone responses and eight types involved in stress responses. Moreover, the transcript levels of CsSWEET genes were analyzed in various tissues using quantitative real-time polymerase chain reaction. A majority (70.58%) of the CsSWEET genes were confined to reproductive tissue development. Finally, 18 putative watermelon ClaSWEET genes and 18 melon CmSWEET genes were identified that showed a high degree of similarity with CsSWEET genes. The results from this study provided a basic understanding of the CsSWEET genes and may also facilitate future research to elucidate the function of SWEET genes in cucumber and other Cucurbitaceae crops.

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Effects of molybdenum on nutrition, quality, and flavour compounds of strawberry (Fragaria×ananassa Duch. cv. Akihime) fruit LIU Li, XIAO Wei, JI Mei-ling, YANG Chao, LI Ling, GAO Dong-sheng, FU Xi-ling 2017, 16(07): 1502-1512.  DOI: 10.1016/S2095-3119(16)61518-6 Abstract ( )   PDF in ScienceDirect       Molybdenum (Mo) is an essential trace element in plant nutrition and physiology. It affects photosynthesis and photosynthate accumulation, therefore also affecting fruit quality and nutritional content. This study assessed the effects of different sodium molybdate (Na2MoO4) concentrations on strawberry. Five different Mo concentrations were applied in this experiment, including 0, 67.5, 135, 168.75, 202.5 g ha–1, respectively. The mineral concentration, including nitrogen (N), Mo, iron (Fe), copper (Cu), and selenium (Se) was assessed in strawberry fruit, as well as chlorophyll content, nutrition quality, taste and aroma. Results showed that net photosynthetic rate (Pn) and chlorophyll content for the strawberry plants increased with an increase in Mo concentration; and the contents of N, Mo, Fe, Cu, total soluble solids (TSS), titratable acidity (TA), sweetness, some sugars, organic acids, and some volatile compounds in the fruit all increased, as well. However, the Mo concentration did not significantly affect the concentrations of Se, sucrose, lactic acid, acetic acid, and some aroma compounds. Fruit sprayed with 135 g ha–1 Mo exhibited the highest TSS and sweetness values, as well as the highest N and Fe concentrations among all the treatments. Pn value and chlorophyll content, fructose, glucose, sorbitol and total sugar contents in fruit supplied with 135 g ha–1 Mo were also higher than that in other treatments. Fruit sprayed with a Mo concentration of 67.5 g ha–1 exhibited significantly higher ascorbic acid (AsA) values than that of control. Ninety-seven volatile compounds were identified in fruit extracted by head-space solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Fruits sprayed with 135 g ha–1 Mo had the highest concentrations of six characteristic aroma compounds, including methyl butanoate, γ-decalactone, ethyl butanoate, methyl hexanoate, γ-dodecalactone, and ethyl caproate.

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Ca(NO3)2 canopy spraying during physiological fruit drop period has a better influence on the tree character and fruit quality of Newhall navel orange (Citrus sinensis Osbeck) ZHENG Yong-qiang, YANG Qiong, JIA Xue-mei, LIU Yan-mei, HE Shao-lan, DENG Lie, XIE Rang-jin, YI Shi-lai, Lü Qiang 2017, 16(07): 1513-1519.  DOI: 10.1016/S2095-3119(16)61603-9 Abstract ( )   PDF in ScienceDirect       This study aimed to provide a theoretical basis for adopting suitable cultivation measures to tackle calcium (Ca) deficiency in citrus leaves. The Newhall navel orange (Citrus sinensis Osbeck) canopy was sprayed with 20.0 mmol L–1 of Ca(NO3)2 during physiological fruit drop period, fruit expanding period, and fruit maturing period on 30, 90, and 210 days after full bloom (DAFB), respectively, and its effects on leaf gas exchange parameters and leaf mineral nutrition and fruit quality were analyzed. The results showed that: (1) The photosynthetic rate (ACO2) at 9:00 a.m. and 16:00 p.m. of fruit expanding period with 30 and 90 DAFB Ca(NO3)2 treatments slightly or significantly improved mainly by decreasing stomatal limitation and nonstomatal limitation, respectively. (2) Compared with control (CK), the Ca concentration in leaves with 30, 90, and 240 DAFB Ca(NO3)2 treatments increased by 127.16, 97.53, and 33.33%, respectively, and the leaf magnesium concentration also increased by more than 32.26%. However, Ca(NO3)2 canopy spraying on 30 DAFB significantly reduced the leaf potassium concentration, by 22.14% compared with CK. (3) Ca(NO3)2 canopy spraying on 30 DAFB decreased the second fruit drop rate by 30.55% and increased the weight per fruit by 25.04%, thus resulting in a significant increase in citrus yield. (4) Spraying Ca(NO3) on 30 DAFB mainly affected the metabolism of titratable acid (TA) to improve the maturity of citrus fruits. Whilst it improved the external quality and the coloring of citrus fruit significantly. Therefore, Ca(NO3)2canopy spraying during physiological fruit drop period has a better influence on the tree character and fruit quality of Newhall navel orange (Citrus sinensis Osbeck).

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Using a process-oriented methodology to precisely evaluate temperature suitability for potato growth in China using GIS HE Ying-bin, ZHOU Yang-fan, CAI Wei-min, WANG Zhuo-zhuo, DUAN Ding-ding, LUO Shan-jun, CHEN Jing-zhu 2017, 16(07): 1520-1529.  DOI: 10.1016/S2095-3119(16)61627-1 Abstract ( )   PDF in ScienceDirect       A process-oriented methodology to conduct precise evaluation temporally and spatially on temperature suitability for potato growth was applied in China. Arable lands in China were gridded with 1 km×1 km geographic units, and potential potato phenology in each unit was automatically identified in terms of the potato planting initial temperature and effective accumulated temperature. A temperature thermal response coefficient model was used to compute a temperature suitability value for each day of potato phenology in each geographic unit. In addition, five temperature suitability ranking methods were applied to define suitable areas: (1) upper fourth quantile, (2) median, (3) expected value+1/4 standard deviation, (4) expected value+1/2 standard deviation, (5) expected value+1 standard deviation. A validation indicator was innovated to test the effectiveness of the five ranking methods. The results showed that from a strict degree point of view, the five methods sequence was as follows: 1=3>4>2>5, with a and c determined as the two best ranking methods. For methods 1 and 3, the suitable potato growing area was 1 of 57.76×104 km2. In addition, the suitable areas were spatially coincident with the main potato producing counties. The study output technically supports the proposal from China’s government that there is a large potential area to grow winter-ploughed potato in South China because the potential suitable area for growing potato is approximately 2×107 ha. In southeast Heilongjiang and east Jilin, where it is hilly and mountainous, there are still some potentially suitable areas for potato growing accounting for nearly 2.32×106 ha. The authors suggest to optimize the agricultural regionalization and layout in China and to adjust the cropping pattern structure.

Plant Protection

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The composition of Fusarium species in wheat husks and grains in south-eastern Poland Adam Kuzdraliński, Micha? Nowak, Hubert Szczerba, Karolina Dudziak, Marta Muszyńska, Justyna Le?niowska-Nowak 2017, 16(07): 1530-1536.  DOI: 10.1016/S2095-3119(16)61552-6 Abstract ( )   PDF in ScienceDirect       Fusarium populations were investigated on 53 samples of wheat grains and husks collected approximately three weeks before harvest in 53 wheat fields in south-eastern Poland. A limited area of sample collection was chosen intentionally to avoid the effect of climate and weather variability. The study was conducted to assess the occurrence of 13 Fusarium species using species-specific PCR assays separately on grains and husks of winter wheat. The obtained data suggest that husks could take a protective role of wheat grain against Fusarium spp. The incidence of Fusarium species decreased in grains vs. husks from 29 to 100%. While Fusarium species were present in husks at 11.32% and less, they were absent in the grain. The presence of Fusarium species on husks is inversely proportional to the percentage reduction of Fusarium spp. in grain. There was a correlation of the presence of certain species of Fusarium in husks and in grains. The number of Fusarium species found on husks was about three times higher in comparison to wheat grain. In conclusion, the presented data indicate the importance of Fusarium populations analysis on wheat husk in seeds pathological studies.

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Golden Promise barley (Hordeum vulgare) is a suitable candidate model host for investigation interaction with Heterodera avenae LUO Shu-jie, KONG Ling-an, PENG Huan, HUANG Wen-kun, CUI Jiang-kuan, LIU Jing, QIAO Fen, JIAN Heng, PENG De-liang 2017, 16(07): 1537-1546.  DOI: 10.1016/S2095-3119(16)61595-2 Abstract ( )   PDF in ScienceDirect       Heterodera avenae (cereal cyst nematode, CCN) infects many cereal crops and causes serious yield losses worldwide. Interaction studies investigating H. avenae and its hosts are still in their infancy. In this study, a barley model plant, the Hordeum vulgare cultivar Golden Promise, was investigated for its potential as a candidate model host to study its interaction with H. avenae. CCN-infective juveniles were attracted by the root tips and gathered around the root elongation zones of Golden Promise on 0.7% water agar plates. The juveniles invaded the roots and developed successfully until maturation at 40 days after inoculation in sterile sand soil. The cryotomy and syncytium measurements indicated that the syncytia enlarged gradually throughout the development of the nematodes and caused the corresponding root regions to swell obviously. Quantitative real-time PCR analysis showed that the down-regulation of defence-related barley genes and up-regulation of development-related barley genes contribute to the understanding of compatible interaction between H. avenae and Golden Promise. Barley stripe mosaic virus (BSMV) virus-induced gene silencing (VIGS) can be used in the roots of Golden Promise. In conclusion, the Hordeum vulgare cultivar Golden Promise is a suitable candidate model host for interaction studies with Heterodera avenae. The studies presented above document the first CCN host that not only has published genome context but also be compatible to BSMV VIGS.

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Automated detection and identification of white-backed planthoppers in paddy fields using image processing YAO Qing, CHEN Guo-te, WANG Zheng, ZHANG Chao1 YANG Bao-jun, TANG Jian 2017, 16(07): 1547-1557.  DOI: 10.1016/S2095-3119(16)61497-1 Abstract ( )   PDF in ScienceDirect       A survey of the population densities of rice planthoppers is important for forecasting decisions and efficient control. Traditional manual surveying of rice planthoppers is time-consuming, fatiguing, and subjective. A new three-layer detection method was proposed to detect and identify white-backed planthoppers (WBPHs, Sogatella furcifera (Horváth)) and their developmental stages using image processing. In the first two detection layers, we used an AdaBoost classifier that was trained on a histogram of oriented gradient (HOG) features and a support vector machine (SVM) classifier that was trained on Gabor and Local Binary Pattern (LBP) features to detect WBPHs and remove impurities. We achieved a detection rate of 85.6% and a false detection rate of 10.2%. In the third detection layer, a SVM classifier that was trained on the HOG features was used to identify the different developmental stages of the WBPHs, and we achieved an identification rate of 73.1%, a false identification rate of 23.3%, and a 5.6% false detection rate for the images without WBPHs. The proposed three-layer detection method is feasible and effective for the identification of different developmental stages of planthoppers on rice plants in paddy fields.

Animal Science · Veterinary Science

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Association of CYP19A1 gene polymorphisms with reproductive traits in pigs ZHOU Rong, YANG Ya-lan, LIU Ying, CHEN Qi-mei, CHEN Jie, LI Kui 2017, 16(07): 1558-1565.  DOI: 10.1016/S2095-3119(16)61520-4 Abstract ( )   PDF in ScienceDirect       Porcine reproductive traits are characterized by low heritability, making improvement by traditional selective breeding rather difficult. Molecular breeding offers powerful approaches to overcome previous limitations and is expected to generate economic benefits via progress in pig breeding. Cytochrome P450 family 19 subfamily A polypeptide 1 (CYP19A1) gene is a key enzyme of estradiol biosynthesis that plays an important role in the establishment of gestation and maintenance of pregnancy. In this study, the sequence and structure characteristics of the porcine CYP19A1 gene was analyzed and expression patterns of CYP19A1 in different tissues of adult female pigs were detected. Fourteen single-nucleotide polymorphisms (SNPs) in the exons and introns of porcine CYP19A1 were identified and genotyped using the Sequenom MassARRAY platform, after which the allele frequency of each SNP was analyzed. The association between CYP19A1 SNPs and litter size and piglet birth weight was assessed in a crossbred pig population (n=375). The expression pattern of CYP19A1 revealed that it was highly expressed in the ovary, spleen, and uterus and lowly expressed in the other tissues. Moreover, one SNP, rs341891833, was significantly associated with piglet birth weight during the multiparity period (P<0.01). We concluded that CYP19A1 could be used as a candidate molecular marker in breeding aimed at rapid improvement of the reproductive characteristics of pigs.

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In vitro investigation of the effect of dairy propionibacteria on rumen pH, lactic acid and volatile fatty acids Jianbiao Luo, Chaminda Senaka Ranadheera, Stuart King, Craig Evans, Surinder Baines 2017, 16(07): 1566-1575.  DOI: 10.1016/S2095-3119(16)61556-3 Abstract ( )   PDF in ScienceDirect      Ruminal acidosis is a prevalent disorder in ruminants such as dairy cows and feedlot beef cattle, caused primarily by the inclusion of a high percentage of readily fermentable concentrates in the diet. The disorder presents as an accumulation of lactic acid, a decrease of pH in the rumen and a subsequent imbalance of the rumen fermentation process with detrimental impacts on the animal’s health and productivity. Dairy propionibacteria, a group of bacteria characterised by utilization of lactic acid as the favoured carbon source, with propionic acid produced as a by-product, were evaluated in this study as potential direct-fed microbials for use in controlling ruminal acidosis. Acidosis was simulated by introduction of high concentrations of lactic acid into rumen fluid samples and a multi-strain in vitro analysis was conducted, whereby changes in pH and lactic acid metabolism were compared in identical acidified rumen samples, following inoculation with various propionibacteria. This was followed by a study to evaluate the effect of bacterial inoculation dosage on acid metabolism. The results indicated that lactic acid levels in the rumen fluid were significantly reduced, and propionic acid and acetic acid concentrations both significantly increased, following addition of propionibacteria. Significant ‘between strains’ differences were observed, with Propionibacterium acidopropionici 341, Propionibacterium freudenreichii CSCC 2207, Propionibacterium jensenii NCFB 572 and P. jensenii 702 each producing more rapid reduction of lactic acid concentration than P. freudenreichii CSCC 2206, P. acidopropionici ATCC 25562 and Propionibacterium thoenii ATCC 4874. Furthermore, the efficacy of this application was dosage related, with the rates of reduction in lactic acid levels and production of propionic acid, both significantly greater for the higher (1010 cfu mL–1) compared with lower (105 cfu mL–1) dosage inoculation. The results confirmed that the introduction of propionibacteria could promote more rapid reduction of lactic acid levels than would occur without their addition, demonstrating their potential in controlling ruminal acidosis.

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In silico genome-wide identification, phylogeny and expression analysis of the R2R3-MYB gene family in Medicago truncatula ZHENG Xing-wei, YI Deng-xia, SHAO Lin-hui, LI Cong 2017, 16(07): 1576-1591.  DOI: 10.1016/S2095-3119(16)61521-6 Abstract ( )   PDF in ScienceDirect       The R2R3-MYB genes make up one of the largest transcription factor families in plants, and play regulatory roles in various biological processes such as development, metabolism and defense response.  Although genome-wide analyses of this gene family have been conducted in several species, R2R3-MYB genes have not been systematically analyzed in Medicago truncatula, a sequenced model legume plant.  Here, we performed a comprehensive, genome-wide computational analysis of the structural characteristics, phylogeny, functions and expression patterns of M. truncatula R2R3-MYB genes.  DNA binding domains are highly conserved among the 155 putative MtR2R3-MYB proteins that we identified.  Chromosomal location analysis revealed that these genes were distributed across all eight chromosomes.  Results showed that the expansion of the MtR2R3-MYB family was mainly attributable to segmental duplication and tandem duplication.  A comprehensive classification was performed based on phylogenetic analysis of the R2R3-MYB gene families in M. truncatula, Arabidopsis thaliana and other plant species.  Evolutionary relationships within clades were supported by clade-specific conserved motifs outside the MYB domain.  Species-specific clades have been gained or lost during evolution, resulting in functional divergence.  Also, tissue-specific expression patterns were investigated.  The functions of stress response-related clades were further verified by the changes in transcript levels of representative R2R3-MYB genes upon treatment with abiotic and biotic stresses.  This study is the first report on identification and characterization of R2R3-MYB gene family based on the genome of M. truncatula, and will facilitate functional analysis of this gene family in the future.

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Effect of lactic acid bacteria and propionic acid on conservation characteristics, aerobic stability and in vitro gas production kinetics and digestibility of whole-crop corn based total mixed ration silage CHEN Lei, YUAN Xian-jun, LI Jun-feng, WANG Si-ran, DONG Zhi-hao, SHAO Tao 2017, 16(07): 1592-1600.  DOI: 10.1016/S2095-3119(16)61482-X Abstract ( )   PDF in ScienceDirect       This study was conducted to evaluate the effect of lactic acid bacteria and propionic acid on the fermentation quality, aerobic stability and in vitro gas production kinetics and digestibility of whole-crop corn based total mixed ration (TMR) silage. Total mixed ration was ensiled with four treatments: (1) no additives (control); (2) an inoculant (Lactobacillus plantarum) (L); (3) propionic acid (P); (4) propionic acid+lactic acid bacteria (PL). All treatments were ensiled in laboratory-scale silos for 45 days, and then subjected to an aerobic stability test for 12 days. Further, four TMR silages were incubated in vitro with buffered rumen fluid to study in vitro gas production kinetics and digestibility. The results indicated that all TMR silages had good fermentation characteristics with low pH (<3.80) and ammonia nitrogen (NH3-N) contents, and high lactic acid contents as well as Flieg points. Addition of L further improved TMR silage quality with more lactic acid production. Addition of P and PL decreased lactic acid and NH3-N contents of TMR silage compared to the control (P<0.05). After 12 days aerobic exposure, P and PL silages remained stable, but L and the control silages deteriorated as indicated by a reduction in lactic acid and an increase in pH, and numbers of yeast. Compared to the control, addition of L had no effects on TMR silage in terms of 72 h cumulative gas production, in vitro dry matter digestibility, metabolizable energy, net energy for lactation and short chain fatty acids, whereas addition of PL significantly (P<0.05) increased them. L silage had higher (P<0.05) in vitro neutral detergent fiber digestibility than the control silage. The results of our study suggested that TMR silage prepared with whole-crop corn can be well preserved with or without additives. Furthermore, the findings of this study suggested that propionic acid is compatible with lactic acid bacteria inoculants, and when used together, although they reduced lactic acid production of TMR silage, they improved aerobic stability and in vitro nutrients digestibility of TMR silage.

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The codon-optimized capsid gene of duck circovirus can be highly expressed in yeast and self-assemble into virus-like particles YANG Cui, XU Yu, JIA Ren-yong, LIU Si-yang, WANG Ming-shu, ZHU De-kang, CHEN Shun, LIU Ma-feng, ZHAO Xin-xin, SUN Kun-feng, JING Bo, YIN Zhong-qiong, CHENG An-chun 2017, 16(07): 1601-1608.  DOI: 10.1016/S2095-3119(16)61605-2 Abstract ( )   PDF in ScienceDirect       The capsid (Cap) protein, which is the only structural protein of duck circovirus (DuCV), is the most important antigen for the development of vaccines against DuCV and the virus’s serological diagnostic methods. In order to use yeast expression system to produce a large quantities of DuCV Cap protein which is close to its natural form to display the antigen peptides perfectly, the Cap gene was optimized into the codon-optimized capsid (Opt-Cap) gene towards the preference of yeast firstly. Then, the genes of Cap and Opt-Cap were separately cloned into pPIC9K plasmid and transformed into Picha pastoris GS115. The strains that displayed the phenotype of Mut+ and contained multiple inserts of expression cassette were selected from those colonies. After the induction expression, the secretory type of Cap protein, which was about 43 kDa, was best expressed under 0.5% (v/v) methanol and sorbitol induction. Compared with the Cap gene, the expression level of Opt-Cap gene was much higher. What’s more, the purified Cap protein had a good reactivity to its specific polyclone antibody and DuCV-positive serum, and it was able to self-assemble into virus-like particles (VLPs). These VLPs, with a diameter of 15–20 nm and without a nucleic acid structure, showed a high level of similarity to DuCV particles in size and shape. All of the results demonstrated that, based on the codon-optimization, it is suitable to use the P. pastoris expression system to produce DuCV VLPs on a large scale. It is the first time that a large amounts of DuCV VLPs were produced successfully in P. pastoris, which might be particularly useful for the further studies of serological diagnosis and vaccines of DuCV.

Agro-Ecosystem & Environment

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Soil boron fertilization: The role of nutrient sources and rootstocks in citrus production Dirceu Mattos Jr, Franz W R Hippler, Rodrigo M Boaretto, Eduardo S Stuchi, José A Quaggio 2017, 16(07): 1609-1616.  DOI: 10.1016/S2095-3119(16)61492-2 Abstract ( )   PDF in ScienceDirect      Boron (B) is a key element for citrus production, especially in tropical regions, where the nutrient availability is commonly low in the soil. In addition, information about doses, fertilizer sources, methods of application, and particularly, differential nutrient demand of scion/rootstock combinations are required for efficient fertilization of commercial groves. In a non-irrigated sweet orange orchard (cv. Natal), grafted onto Rangpur lime, Swingle citrumelo or Sunki mandarin, we studied the application of two sources of B: boric acid (17% B, soluble in water) and ulexite (12% B, partially soluble in water) at four levels of supply (control without B, and soil application of 2, 4 and 6 kg ha–1 yr–1 of B). The experiment was carried out for three years (2004-2006). Boron availability in the soil and concentration in the leaves, as well as the fruit yield and quality of trees were evaluated. Soil B extracted with hot water and total leaf B positively correlated with doses of the nutrient applied to the trees. Levels of B in the soil and in the leaves did not vary with fertilizer sources. Fruit yield of trees grafted onto Rangpur lime and Swingle citrumelo was more responsive to B doses than those grafted onto Sunki mandarin. The maximum fruit yield of trees grafted onto Swingle was obtained with 3.2 kg ha–1 yr–1 of B, and leaf B level of 280 mg kg–1 that point out to a highest demand for B when this combination was compared with other rootstocks. Furthermore, fertilization with B did not affect the quality of fruits, but correlated with B and potassium (K) concentrations in the leaves. These results also support that the current recommendations for levels of B in leaves should be revisited.

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Effect of Zn application methods on Zn distribution and bioavailability in wheat pearling fractions of two wheat genotypes LI Meng, TIAN Xiao-hong, LI Xiu-li, WANG Shao-xia 2017, 16(07): 1617-1623.  DOI: 10.1016/S2095-3119(17)61657-5 Abstract ( )   PDF in ScienceDirect   Pearling is an effective method for evaluating the distribution of chemical components in wheat grain. Five pearling fractions (representing approximately 20% of the original sample weight) of wheat grain were obtained using the JNMJ3 rice polisher for two cultivars with different methods of Zinc (Zn) application; the residual portion (approximately 80%) was ground as flour. Results showed that foliar or soil+foliar Zn application methods effectively increased Zn concentrations and bioavailability in whole grain and pearling fractions, but soil Zn application was ineffective in field conditions. In addition, the concentrations of Zn, Fe, Mn and Cu within wheat grain showed a diminishing trend from the outer layer to the inner portions of the wheat grain as the pearling level increased. These results clearly showed the distribution of minerals in wheat grain, especially in the outer part of the grain (bran). The results also suggest that precise milling techniques combined with foliar Zn application could improve the Zn and Fe nutritional qualities of consumed flour and mitigate human Zn and Fe deficiencies.

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Effects of soil salinity on rhizosphere soil microbes in transgenic Bt cotton fields LUO Jun-yu, ZHANG Shuai, ZHU Xiang-zhen, LU Li-min, WANG Chun-yi, LI Chun-hua, CUI Jin-jie, ZHOU Zhi-guo 2017, 16(07): 1624-1633.  DOI: 10.1016/S2095-3119(16)61456-9 Abstract ( )   PDF in ScienceDirect       With increased cultivation of transgenic Bacillus thuringiensis (Bt) cotton in the saline alkaline soil of China, assessments of transgenic crop biosafety have focused on the effects of soil salinity on rhizosphere microbes and Bt protein residues. In 2013 and 2014, investigations were conducted on the rhizosphere microbial biomass, soil enzyme activities and Bt protein contents of the soil under transgenic Bt cotton (variety GK19) and its parental non-transgenic cotton (Simian 3) cultivated at various salinity levels (1.15, 6.00 and 11.46 dS m−1). Under soil salinity stress, trace amounts of Bt proteins were observed in the Bt cotton GK19 rhizosphere soil, although the protein content increased with cotton growth and increased soil salinity levels. The populations of slight halophilic bacteria, phosphate solubilizing bacteria, ammonifying bacteria, nitrifying bacteria and denitrifying bacteria decreased with increased soil salinity in the Bt and non-Bt cotton rhizosphere soil, and the microbial biomass carbon, microbial respiration and soil catalase, urease and alkaline phosphatase activity also decreased. Correlation analyses showed that the increased Bt protein content in the Bt cotton rhizosphere soil may have been caused by the slower decomposition of soil microorganisms, which suggests that salinity was the main factor influencing the relevant activities of the soil microorganisms and indicates that Bt proteins had no clear adverse effects on the soil microorganisms. The results of this study may provide a theoretical basis for risk assessments of genetically modified cotton in saline alkaline soil.

Food Science

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Prediction of kiwifruit firmness using fruit mineral nutrient concentration by artificial neural network (ANN) and multiple linear regressions (MLR) Ali Mohammadi Torkashvand, Abbas Ahmadi, Niloofar Layegh Nikravesh 2017, 16(07): 1634-1644.  DOI: 10.1016/S2095-3119(16)61546-0 Abstract ( )   PDF in ScienceDirect       Many properties of fruit are influenced by plant nutrition. Fruit firmness is one of the most important fruit characteristics and determines post-harvest life of the fruit. In recent decades, artificial intelligence systems were employed for developing predictive models to estimate and predict many agriculture processes. In the present study, the predictive capabilities of multiple linear regressions (MLR) and artificial neural networks (ANNs) are evaluated to estimate fruit firmness in six months, including each of nutrients concentrations (nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg)) alone (P1), combination of nutrients concentrations (P2), nutrient concentration ratios alone (P3), and combination of nutrient concentrations and nutrient concentration ratios (P4). The results showed that MLR model estimated fruit firmness more accuracy than ANN model in three datasets (P1, P2 and P4). However, the application of P3 (N/Ca ratio) as the input dataset in ANN model improved the prediction of fruit firmness than the MLR model. Correlation coefficient and root mean squared error (RMSE) were 0.850 and 0.539 between the measured and the estimated data by the ANN model, respectively. Generally, the ANN model showed greater potential in determining the relationship between 6-mon-fruit firmness and nutrients concentration.

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Penicillium and patulin distribution in pears contaminated with Penicillium expansum. Determination of patulin in pears by UHPLC-MS/MS WEI Dong-mei, XU Jun, DONG Feng-shou, LIU Xin-gang, WU Xiao-hu, ZHENG Yong-quan 2017, 16(07): 1645-1651.  DOI: 10.1016/S2095-3119(16)61543-5 Abstract ( )   PDF in ScienceDirect       The danger of mycotoxin contamination entering the food supply through post-harvest infection is of perennial concern to food safety experts. To explore the distribution of Penicillium expansum and diffusion of its mycotoxin, patulin, in blue mold-damaged pears, Pyrus bretschneideri Rehd. cv. Yali obtained from markets and orchards in China were artificially inoculated with P. expansum and assayed for patulin accumulation and degree of fungal colonization. The inoculated pears were incubated until the lesions were 5, 10, 20, or 30 mm in diameter. We sampled tissue at a range of distances from the lesion, measured the spread of Penicillium by plate colony-counting methods, and used UHPLC-MS/MS to detect and quantify the patulin concentration. More P. expansum colony-forming units were isolated from pears with a higher degree of decay. Farther from the lesion, the fewer P. expansum colonies were observed, and the lower the patulin content detected. We found a significant difference in the patulin content between samples due to lesion size, and also in tissue sampled 10 mm away from the lesion. In consideration of this finding, to ensure food safety, we recommend that when a blue mold rot lesion on pear is 5, 10, or 20 mm in diameter, 20, 30, and 40 mm beyond the lesion should be removed, respectively. If a lesion surpasses 30 mm in diameter, the whole pear should be thrown away.