Table of Content

01 February 2016, Volume 49 Issue 3

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

The Correlation of Stem Characters and Lodging Resistance and Combining Ability Analysis in Rice

CHEN Gui-hua, DENG Hua-bing, ZHANG Gui-lian, TANG Wen-bang, HUANG Huang

Scientia Agricultura Sinica. 2016, 49(3):  407-417.  doi:10.3864/j.issn.0578-1752.2016.03.001

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【Objective】 Lodging is one of the main constraints to the yield of rice. This study investigated the relationships among stem morphological index, chemical constituents and anatomical structure with lodging resistance. The combining ability of lodging related traits were analyzed. Results of the study will provide a theoretical basis for breeding of high yield rice varieties with lodging resistance.【Method】Three new rice dual-purpose genic male sterile lines and 5 restorer lines were crossed using incomplete diallel crosses and 15 hybrid combinations as materials in 2014. Four new rice dual-purpose genic male sterile lines and 3 restorer lines were crossed using incomplete diallel crosses and 12 hybrid combinations as materials in 2015. The anti-thrust per stem was used as the lodging resistance index. The correlation of stem morphological index and chemical constituents and anatomical structure with lodging resistance and the combining ability variance analysis of lodging resistance of tested combinations and the general combining ability of parents were studied. 【Result】The anti-thrust per stem was positively correlated with stem length, fresh weight per stem, bending moment, crude fiber content, silicon content and the number of small vascular bundles in both 2014 and 2015. Stepwise regression analysis in 2014 showed that bending moment and silicon content and the number of small vascular bundles had a positive effect on the anti-thrust per stem. Stepwise regression analysis in 2015 showed that stem length and stem diameter and crude fiber content and the number of small vascular bundles had a positive effect on the anti-thrust per stem. The number of small vascular bundles was included in the regression equation in two years of testing. The variance of special combining ability and general combining ability of sterile lines of the anti-thrust per stem all reached significant level in two years. Further analysis showed that the variance of general combining ability of sterile lines was larger than the variance of general combining ability of restorer lines and special combining ability of the trait. The anti-thrust per stem of sterile lines 075S and 023S, and that of restorer lines R276 and R964 and R527 and R389 had higher general combining ability. 【Conclusion】Stem length, fresh weight per stem, bending moment, crude fiber content and silicon content of stem, the number of small vascular bundles were main influencing factors of lodging resistance of rice. The anti-thrust per stem was controlled by both additive and non-additive gene. The additive gene effect of sterile lines had great influence on lodging resistance of hybridized combination. The anti-thrust per stem of sterile lines 075S and 023S and that of restorer lines R276 and R964 and R527 and R389 had higher general combining ability. The six parents could be used as parents of hybrid rice combinations for lodging resistance.

Development and Genetic Analysis of a Novel Wheat-Aegilops Germplasm TA002 Resistant to Powdery Mildew

WANG Yu-hai, HE Fang, BAO Yin-guang, MING Dong-feng, DONG Lei, HAN Qing-dian, LI Ying-ying, WANG Hong-gang

Scientia Agricultura Sinica. 2016, 49(3):  418-428.  doi:10.3864/j.issn.0578-1752.2016.03.002

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【Objective】 Powdery mildew is one of the most devastating diseases of wheat. It is widely accepted that the most economic, efficient and safest way to control powdery mildew is breeding and planting powdery mildew resistant cultivars. Aegilops ventricosa and Aegilops cylindrica, which possess many favorable characters and good qualities such as resistance to diseases, tolerance to environmental stresses, are close-related relatives of wheat. The objective of this study was to develop novel powdery mildew resistant germplasm line via wide hybridization between common wheat and Aegilops ventricosa and/or Aegilops cylindrica for genetic improvement. 【Method】 Improved fuchsin squash and seed set examination were used to determine the cytogenetic stability and fertility of TA002. Acid polyacrylamide gel electrophoresis (A-PAGE) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to analyze the subunit composition of gliadin, high and low molecular weight glutenin (HMW-GS and LMW-GS) respectively. Genomic in situ hybridization (GISH), multicolor genomic in situ hybridization (mc-GISH), multicolor fluorescence in situ hybridization (mc-FISH) and molecular markers were employed to detect the genetic nature of TA002. Respective inoculation of powdery mildew isolates was performed to detect the reaction of TA002 to powdery mildew.【Result】 TA002 (2n = 42) showed equivalent seed set to that of common wheat. Both TA002 and its hybrid F₁ with common wheat Mingxian169 housed 21 bivalents in the pollen mother cells observed at metaphase I (PMCs MI) and took on chromosomal segregation of 21 to 21 in pollen mother cells examined at anaphase I (PMCs AI). Contrast to wheat parent Yannong15 highly susceptible to powdery mildew, TA002, similar to SDAU18 and its parents Aegilops ventricosa and Aegilops cylindrica, was highly resistant to powdery mildew. Immunization and resistant-susceptible segregation of 3﹕1 was observed respectively in F₁ and F₂ of the crosses between TA002 and common wheats susceptible to powdery mildew. The analysis of seed storage proteins of TA002 and its parents revealed that TA002 not only had new glutenin and gliadin subunits specific to SDAU18, but also possessed a novel gliadin subunit derived from its neither parents. When probed respectively by genomic DNA of Aegilops uniaristata and Aegilops caudata in root tip cell chromosomes of TA002, no probe signals were detected. Multicolor genomic in situ hybridization (mc-GISH) and multicolor fluorescence in situ hybridization (mc-FISH) indicated that TA002 had three complete genomes (A, B and D) although five pairs of chromosomes 4A, 5A,6B, 7B and 5D in it showed significantly different FISH pattern from that of corresponding ones in Yannong15. Mc-GISH was carried out simultaneously using genomic DNA of Triticum uratu and that of Aegilops tauschii labeled with different fluoresceins as probes, and with genomic DNA of Aegilops speltoides as blocker. Mc-FISH was performed with two oligonucleotides pSc119.2 and pTa-535 fluorescing differently. Molecular marker analysis revealed TA002 housed alien genetic materials not only from Aegilops ventricosa but also from Aegilops cylindrica. 【Conclusion】TA002, derived from Aegilops ventricosa or Aegilops cylindrica with high powdery mildew resistance controlled by a single dominant gene, was found as a novel wheat-Aegilops introgression line of cytogenetic stability and good fertility. In addition, TA002 possessed novel seed storage protein subunits either specific to Aegilops ventricosa -Aegilops cylindrica amphiploid or in neither parents.

Responses of Endoplasmic Reticulum Stress-Related Genes in Maize Embryo to Artificial Aging Treatment

CAO Guang-can, LIN Yi-xin, XUE Mei-zhen, XING Lu-man, Lü Wei-zeng, YANG Wei-fei, CHEN Jun-ying

Scientia Agricultura Sinica. 2016, 49(3):  429-442.  doi:10.3864/j.issn.0578-1752.2016.03.003

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【Objective】 Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are involved in plant responses to environmental stresses. However, the expression of ER stress-related genes during maize seed aging has not been reported. In this study, the expression of ER stress-related genes during maize seed aging was investigated by Digital Gene Expression Profile (DGE) to provide theoretical support for clarifying the molecular mechanism of seed deterioration.【Method】 Hybrid maize (Zea mays L.) cultivar Zhengdan 958 seeds were used as experimental material and treated by artificial aging treatment (45℃, 100% relative humidity). DGE analysis was carried out on the Illumina Hiseq 2000 platform using total RNA extracted from 3 d artificial aging treatment and the untreated embryos (CK) of maize seeds. The reads with adaptor and ambiguous sequences, and the low-quality reads were filtered out to obtain the high quality clean reads. Clean reads were mapped to the maize reference genome and genes database using SOAPaligner/SOAP2. The gene expression level was calculated by the RPKM (Reads Per kb per million reads) method. A combination of FDR ＜0.001 and the absolute value of |log₂ ratio (T/CK)|≥1 was used as the threshold to determine the significance of gene expression difference. All differentially expressed genes (DEGs) were assigned to the pathways in KEGG (Kyoto Encyclopedia of Genes and Genomes) database and searched for the differentially expressed genes related to ER stress. Quantitative real-time PCR was performed to analyze the expression patterns of ER stress-related genes in the different artificial aging times.【Result】 Analysis of the DGE revealed that 104 DEGs were relevant to the protein processing in ER during the process of artificial aging treatment. A total of 97 DEGs related to ER stress including 81 and 16 genes respectively up- and down-regulated were screened out. The expression levels of ER stress marker BiP gene, as well as ER chaperones, such as CRT, CNT, GRP94 genes were considered to be significantly up-regulated. In particular, 83 DEGs were involved in ER-associated degradation (ERAD) pathway, including 70 up-regulated and 13 down-regulated DEGs. Among them, gene encoding EDEM (ER degradation enhancing mannosidase I-like protein) which is a rate-limiting enzyme of ERAD pathway was down-regulated. Genes involved in protein ubiquitination were altered in expression, including E2 ubiquitin-conjugating enzyme UbcH5, E3 ubiquitin-ligases Hrd1 and Doa10. The results of qRT-PCR analysis validated the diversity and complexity of ER stress-related genes expression in different artificial aging times.【Conclusion】 Artificial aging treatment can cause endoplasmic reticulum stress in maize embryo. The cell can respond to ER stress by inducing up-regulation of ER chaperones genes and activation of the ERAD pathway. Inhibition of ERAD pathway resulted in the accumulation of misfolded proteins in the ER with these leading to further cell damage and subsequently accelerating the loss of seed vigor.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Function and Composition Stability of a Composite Microbial System GF-20 with Efficient Corn Stalk Decomposition Under Low Temperature

Qingge-er, GAO Ju-lin, YU Xiao-fang, HU Shu-ping, WANG Zhi-gang, WANG Zhen, Naoganchaolu BORJIGIN

Scientia Agricultura Sinica. 2016, 49(3):  443-454.  doi:10.3864/j.issn.0578-1752.2016.03.004

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【Objective】 In order to improve the culturing methodology of corn stalk decomposing microbes and promote its utilization, the present study evaluated the impact of different culturing conditions on the community composition of a composite microbial system GF-20 and on its decomposing activity of corn stalk.【Method】 Composite microbial system GF-20 was continuously sub-cultured to the 45th generation under 10℃ and to 15th generation under different temperatures and pH conditions to obtain different microbial communities (F, T, P). Then the dynamics of fermenting pH, corn stalk decomposing ratio and cellulose enzyme activities were determined, so as to estimate the corn stalk decomposing activity of the composite microbial system. Furthermore, the community composition stability was analyzed by PCR-DGGE technique combined with a principal component analysis. 【Result】 The results showed that the pH value tended to be neutral over the fermentation time, and the straw degradation rate ranged in 27.59%-32.53%, in which no difference was shown among the successive 40-generation sub-cultured communities except F40 and F5, neither among the sub-cultured communities under temperature of 4-30℃ and under pH of 6.0-9.0. Cellulose enzyme activity of high generation was higher than that of low generation, and the enzyme production of the microbial community could be promoted under temperature of 4-10℃ and pH of 6.0-9.0, cellulase activity ranged in 1.34-1.84 IU·mL^-1. Cellulase activity of composite microbes showed good stability under lower temperature and in a wide pH range, enzymatic reaction temperature within 15-30℃ and pH within 4.0-9.0 could keep more than 80% of enzyme activity. Furthermore, DGGE bands of F5-F45, T4-T30 and P6-P9 showed no significant differences indicated that the strains composition maintained good stability. However, under acidic (pH=4, 5) or alkaline (pH=10) subculture conditions, the corn stalk degradation rate and cellulase activity significantly decreased, and community composition also changed remarkably, thereby affected the property and functional stability. According to PCR-DGGE profiles, a total of 18 strains were detected, the key strains of which were Bacillus licheniformis, Azonexus hydrophilusd, Azospira oryzae, Arobacter cloacae, Cellvibrio mixtus subsp. Mixtus, Bacillus tequilensis, Clostridium populeti and Clostridium xylanolyticum, respectively. 【Conclusion】Composite microbial community GF-20 sub-cultured under different conditions (temperature 4-30℃, pH 6.0-9.0) kept efficient corn stalk decomposing activity and stable community composition structure, a good application prospect should be anticipated.

Compensation Effect of Different Soybean Varieties in Potato/Soybean Intercropping Systems

CHEN Guang-rong, YANG Wen-yu, ZHANG Guo-hong, WANG Li-ming, YANG Ru-ping, YONG Tai-wen, LIU Wei-guo

Scientia Agricultura Sinica. 2016, 49(3):  455-467.  doi:10.3864/j.issn.0578-1752.2016.03.005

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【Objective】To explore the mechanism of a high yield and an optimum spatial-temporal configuration management in potato-soybean intercropping system. 【Method】This study takes a potato-soybean intercropping system with wildly-used and an apparent yield advantage in Northwest irrigation districts as the research object, a field experiment was conducted in two consecutive seasons (2012-2013), the potato-soybean intercropping trials using three soybean varieties including Zhonghuang 30 (early-maturing variety), Jidou 17 (mid maturing variety ) and Qihuang 34 (late maturing variety ) with the sole cropping potato as the control were carried out to determine the dynamic changes of growth stages of soybean, leaf area index, accumulation of dry matter, photosynthetic characteristics, yield components and yieldin order to optimize the reasonable group configuration.【Result】In comparison with the sole cropping, intercropping system led to a delayed reproductive growth stage of soybean but did not change the whole growth period, the duration from planting to flowering was extended, but the duration from flowering to maturing was shortened. The co-growth stage of different soybean varieties was not affected by intercropping, but the reproductive co-growth stage (from flowering to maturing) was remarkable (P＜0.05, late maturing variety was 12 days, middle-maturing variety was 36 days, early-maturing variety was 42 days).There was a lower increase under intercropping than under sole cropping, the LAI of the late-maturing variety was lower than the mid-maturing and early maturing varieties, significantly (P＜0.05) during earlier growing stage but higher after the potato had been harvested. There was a significant difference in dry matter accumulation between intercropping and sole cropping during the earlier growing stage, dry matter accumulation of inter-soybean relative to the sole soybean was decreased by 55.73% at 60 days after soybean sowing. The Pn varied considerably by different potato-soybean intercropping systems, and lower than the sole soybean, which the late-maturing variety was higher than the mid-maturing and early maturing varieties significantly (P＜0.05).When the potato had been harvested (100 days after soybean sowing), the dry matter accumulation and Pn of soybean in all intercropping systems increased, especially mid-maturing and late-maturing varieties, which became much closer to the sole cropping. Compared with sole cropping, the pods per plant, seeds per plant, and seeds per pod of early-maturing soybean in the intercropping system decreased by 24.15%, 22.14% and 18.92%, respectively (P＜0.05). However, effective pods per plant, seeds per plant, and seeds per pod of the late-maturing soybean decreased by 5.66%, 7.64% and 2.11%, respectively. Finally, the yield of the mid-maturing and late-maturing varieties in intercropping systems are higher than the early-maturing, which increased by 79.85% and 145.08%, with the land equivalent ratio (LER) of 1.77 and 1.83, respectively. 【Conclusion】Mid-maturing and late-maturing varieties were a suitable plant type configuration, the whole growth period was longer, the duration from planting to flowering was extended, but the duration from flowering to maturing was shortened, which could improve the leaf area index, photosynthetic efficiency for compensatory growth when the potato had been harvested, showing the stronger intercropping superiority.

Effect of Potato and Beans Intercropping with Whole Field Plastics Mulching and Ridge-Furrow Planting on Soil Thermal-Moisture Status and Crop Yield on Semi-Arid Area

ZHANG Xu-cheng, WANG Hong-li, YU Xian-feng, HOU Hui-zhi, FANG Yan-jie, MA Yi-fan

Scientia Agricultura Sinica. 2016, 49(3):  468-481.  doi:10.3864/j.issn.0578-1752.2016.03.006

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【Objective】Intercropping is one of the main technologies to solve the potato continuous cropping obstacles, and increase crop productivity. However, it is very important to consider the local soil water capacity before developing a potato intercropping system in the semiarid area.【Method】A 4-year field experiment was carried out from 2011 to 2014 with four treatments: (1) mono-potato (PM), (2) potato and faba bean intercropping (PF), (3) potato and soybean intercropping (PS), and (4) potato and haricot bean intercropping (PH). The soil temperature, soil water content and crop yield had been investigated; the crop water consumption, economic returns and water economic yield were calculated, to understand the effects of different intercropping models on crop productivity and soil moisture. In addition, soil water sustainability was appraised under intercropping system on semiarid area. 【Result】The intercropping relieved the heat stress from June to July, the soil temperature in 0-25 cm profile of PF, PS and PH decreased by 0.8-3.6℃, 0.4-2.8℃ and 0.8-1.8℃ from 2012 to 2014 respectively, as compared with PM, this may advantage to the potato growth. The soil water content decreased, especially, the deeper soil water depleted in intercropping treatments as compared with mono-potato treatment, the depth of soil water depletion reached to 200 cm in the intercropping treatment, compared with PM, the soil water depletion of PF increased by 41.6-131.7 mm in potato pre-flowering period, and decreased by 48.6 mm and 34.3 mm in dry year (2011) and normal year (2012) in post-flowering period respectively. Although the soil water depletion of PH treatment increased in pre-flowering period, but not decreased in post-flowering period significantly, as compared with PM. The variation of soil water depletion in pre- and post-flowering period in PS was between PF and PH. The economic returns and water economic yield of PH was highest, increased by 29.8%-51.4% and 19.8%-24.0% than PM, respectively. The soil water storage in 0-200 cm profile increased more than 100 mm through the 4 experimental years, indicated that there were no adverse effect on soil water sustainability in potato and beans intercropping, when the whole field plastics mulching and ridge-furrow planting technology used in semiarid area. 【Conclusion】Potato and haricot bean intercropping decreased the soil temperature in the hot season (i.e. June and July), increased potato water consumption in post-flowering period, resulted in significant increment of incomes, and had no risk on the annual soil water balance, which could be widely applied in the rain-fed semi-arid area of northwest Loess Plateau.

PLANT PROTECTION

Screening of Putative Proteins That are Interacted with NBS-LRR Protein Pik-h by the Yeast Two-Hybrid System

WANG Jia-feng, LIU Hao, WANG Hui, CHEN Zhi-qiang

Scientia Agricultura Sinica. 2016, 49(3):  482-490.  doi:10.3864/j.issn.0578-1752.2016.03.007

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【Objective】 To further investigate the signaling pathways activated directly by the resistance proteins Pikh-1 and Pikh-2 from the resistance gene Pik-h, yeast two-hybrid assay was performed to screen a rice leaf cDNA library using Pikh-1 and Pikh-2 as bait, respectively. 【Method】 All rice leaves of IRBL8 (Pik-h NIL) from the time points (12 and 24 h after inoculation with GD0193) were harvested for total RNA preparation. The rice leaf cDNA library was further constructed with the Make Your Own Mate&Plate Library System kit (Clontech). Bait plasmids pGBKT7-Pikh1 and pGBKT7-Pikh2 were constructed using the rapid homologous recombination method. The expression of the two proteins in the Y2H Gold strain was further detected with Western blot and the self-activation and cytotoxicity were also tested. Proteins interacting with the baits Pikh1 and Pikh2 were screened on SD/-Ade/-His/-Leu/-Trp/X-α-Gal plates from the rice leaf cDNA library with the mating strategy. Then the plasmids were prepared from the blue interacting clones and retransformed back into Y2H Gold strain with the corresponding bait. The plasmids that passed the reconfirmation were sequenced and the DNA sequences were further used to blast rice genome annotation project database. The functions of the interaction proteins were further analyzed with gene ontology (GO) annotation. 【Result】 The rice leaf cDNA library contained 2.2×10⁶ independent clones. The sizes of most inserts were above 400 bp in the cDNA library. Bait plasmids (pGBKT7-Pikh1 and pGBKT7-Pikh2) expressed the corresponding proteins (BD-Pikh-1 and BD-Pikh-2) well and showed no self-activation and cytotoxicity, and suited to this screen. Thirteen candidate interacting proteins of pGBKT7-Pikh1 and five candidate interacting proteins of pGBKT7-Pikh2 were verified. Function annotation showed that four putative proteins were transcription factors involved in stress response and hormone signaling pathways, three were signaling proteins, four were involved in photosynthesis, one U-BOX containing protein was involved in ubiquitin mediated proteolysis, and four were unknown function proteins. 【Conclusion】 A high quality cDNA library was constructed and 16 proteins interacting with Pik-h proteins were identified, and these results provided good clues for elucidating the Pik-h- or other R-gene-mediated disease-resistant mechanisms in rice.

Effect of RNAi of SmORA1 on Disease Resistance and Tanshinones Secondary Metabolism in Salvia miltiorrhiza

HUA Wen-ping, LIU Wen-chao, WANG Zhe-zhi, LI Cui-qin

Scientia Agricultura Sinica. 2016, 49(3):  491-502.  doi:10.3864/j.issn.0578-1752.2016.03.008

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【Objective】ERF (ethylene responsive factor) are a class of plant-specific transcription factors, which are generally involved in plant stress responses. An ERF gene (named SmORA1) has been screened from medicinal plant Salvia miltiorrhiza, which is highly homologous to CrORCA3 of Catharanthus roseus. The objective of this study is to investigate the effects of SmORA1 on the resistance to disease and on the regulation of tanshinone biosynthesis in S. miltiorrhiza through interference of SmORA1 expression in S. miltiorrhiza by RNAi method.【Method】SmORA1 was cloned and inserted into interference vector, then the constructed vector (pk-ORAi) was transformed into S. miltiorrhiza by Agrobacterium tumefaciens-mediated method and transgenic lines of SmORA1-RNAi were obtained by antibiotic resistance screening and PCR identification. Using the spectrophotometry or enzyme linked immunosorbent assay, the resistance-related enzymes (phenylalnine ammonialyase (PAL), catalase (CAT) and superoxide dismutase (SOD)) activities and physiological indexes (glutathione (GSH), proline (Pro) and malondialdehyde (MDA)) in SmORA1-RNAi transgenic lines were detected after infection by Rhizoctonia solani. The concentrations of tanshinones including dihydrotanshinone, cryptotanshinone and tanshinone II A in SmORA1-RNAi transgenic lines were detected using HPLC method. The expression levels of genes related to resistance and involved in tanshinone biosynthesis were investigated by real-time qPCR.【Result】A total of 11 positive transgenic lines were got after antibiotics and PCR screening, among of which, three lines (RNAi-11, RNAi-18, RNAi-22) with significantly down-regulated expression levels of SmORA1 were obtained after antibiotics and real-time qPCR screening, interference efficiency achieved at 80%. Afterinfection with R. solani, the disease indexes of SmORA1-RNAi lines were significantly higher than those of wild type (WT) and empty vector (VK). The contents of MDA in SmORA1-RNAi lines were also significantly higher than those of control lines, which indicated that the anti-aging ability of transgenic lines was significantly decreased. The activities of SOD, CAT and PAL in SmORA1-RNAi lines were significantly lower than those of the control. The contents of Pro and GSH were also dramatically decreased in SmORA1-RNAi lines. Moreover, the expression levels of SmPDF1.2, SmSTH-2 and SmPR-10 in SmORA1-RNAi lines were down-regulated compared with the control lines. These results implied that SmORA1 play important roles in plant resistance. Furthermore, the expression of SmHMGR1, SmHMGR2, SmGPPS, SmGGPPS1 and SmGGPPS3,encoding key enzymes involved tanshinone biosynthesis, were down-regulated in SmORA1-RNAi lines. Meanwhile, the contents of tanshinone ⅡA and cryptotanshinone were also reduced in SmORA1-RNAi lines compared with the control lines. So it was speculated that SmORA1 regulated tanshinone biosynthesis throught the regulation of the expression of SmHMGR1, SmHMGR2, SmGPPS, SmGGPPS1 and SmGGPPS3. 【Conclusion】SmORA1 is involved in the resistance response and closely related to the regulation of tanshinone biosynthesis in S. miltiorrhiza.

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

Nitrogen Cycling and Management Strategies in Chinese Agriculture

WANG Jing-guo, LIN Shan, LI Bao-guo

Scientia Agricultura Sinica. 2016, 49(3):  503-517.  doi:10.3864/j.issn.0578-1752.2016.03.009

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It is in general thought that nitrogen (N) fertilizer is overused in Chinese croplands and that the overuse has resulted in severe environmental problems. As the biggest reactive nitrogen producer and N fertilizer consumer in the world, China is facing a great challenge to reduce nitrogen consumption in agriculture. The objectives of this review are to examine the sources and fate of reactive nitrogen in agroecosystems, to find out why N fertilizer consumption reaches such a high level, and provide with suggestions for better N management practices. To understand the current agricultural use of reactive N in China, principles of biogeochemical N cycling are used to discuss N flows in the agroecosystems in the year 2010, with focus on N input/output and balances in crop-soil systems. At the national level, input of reactive N to croplands was excessive in 2010, and the surplus was approximately equal to the quantity of the reactive N recycled back to crop fields by atmospheric N deposition and irrigation with N-polluted water, about 5 Tg N. Generally speaking, the use of N fertilizer in cereal crops is not extraordinarily high since N fertilizer is also distributed for other uses: Forestation, feeding livestock and fishes, and application to the green fields in urban areas. It is common and significant that there are much higher N application rates to fruit tree plantations and vegetable production, especially to the greenhouse vegetable growing system, in comparison with that applied to cereal crops. With the facts of the limited arable lands, low recycling rates of organic wastes, and low input of biological fixed N, crop production has to depend heavily on the use of N fertilizer in China. There is a low acreage of arable land per capita, with 8% of global arable land feeding 20% of the world population. Recycled rate of nutrient N in the organic wastes are lower than 30% and input of biological N fixation to croplands is less than 15%. Therefore, to meet the demands of Chinese population for both food and improving diets under the condition of the predominance of the croplands with medium to low productivities, high N fertilizer input is understandable. However, N fertilizer consumption is much higher than the national average in some highly productive regions, including the Huang-Huai-Hai Plain, the Yangtze Basin, and Zhujiang Delta (Guangdong) regions, and is closely connected with higher crop yields/multiple cropping indices, and smaller proportion of legume crops to the total cropping area. It is clear that the N losses from food production-processing-consumption chain have resulted in resource wasting and environmental risks. On the other hand, part of the environment received reactive N from the losses of croplands and the other pollution sources, returns to the fields via atmospheric deposition and the irrigations with polluted waters, and becomes an important source of N input to croplands. Due to the complexity of N transformation in agroecosystems and biogeochemical N cycling, N losses are unavoidable. Therefore, the best management practices at various spatial levels should be taken as the options to reduce the fertilizer use in croplands to the minimum. Integrated measures, including multi-disciplinary researches and the cooperation of various social sectors, have been suggested to optimize N management practices at each spatial level, in order to reach the fundamental goals of maintaining/improving soil fertility, securing food, reducing nitrogen fertilizer use, and minimizing environmental risks.

Effects of Mixed Application of Controlled-Release N Fertilizer and Common Urea on Grain Yield, N Uptake and Soil N Balance in Continuous Spring Maize Production

WANG Yin, FENG Guo-zhong, ZHANG Tian-shan, RU Tie-jun, YUAN Yong, GAO Qiang

Scientia Agricultura Sinica. 2016, 49(3):  518-528.  doi:10.3864/j.issn.0578-1752.2016.03.010

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【Objective】The mixed application of CRN and common urea was considered as a good alternative technique for single basal fertilizer application. This study aimed to evaluate the effects of mixed application of CRN and urea on grain yield, N uptake, N balance in a soil-crop system, and to provide reference to scientific N management techniques for spring maize.【Method】A two-year fixed plot experiment was conducted in the major maize production area in the central Jilin province from 2010 to 2011, including five fertilization treatments, including Treatment I (No N fertilizer, N0), Treatment II (100% urea, CRN0%), Treatment III (15% CRN+85% urea, CRN15%), Treatment IV (30% CRN+70% urea, CRN30%), and Treatment V (45% CRN+55% urea, CRN45%). In this study, grain yield, N uptake, N efficiency of spring maize, soil inorganic N accumulation and mineralization, and N balance in soil-crop system were investigated, and the appropriate mixed ratio of CRN was determined by considering comprehensive performances.【Result】The results showed that mixed application of CRN and urea increased significantly aboveground dry matter and grain yield of spring maize, compared with single basal application of urea, while no differences were found between the various mixed ratios. On an average of two growing seasons, the highest grain yield of 9.39 t·hm^-2 was obtained in the CRN30% treatment, which was 9.0% (0.77 t·hm^-2) higher than that in the CRN0% treatment. Application of N fertilizer was a major way of N input in soil-crop system, which accounted for 63.5% of the total N input, while the contributions of soil inorganic N prior to sowing and N mineralization were 19.2% and 17.3%, respectively. The net N mineralization during maize growing season was 34.4 kg·hm^-2 in 2010 and 66.1 kg·hm^-2 in 2011, while that was in the range of 15.2-26.4 kg·hm^-2 among treatments during the overwintering stage between two growing seasons. Cropped N uptake by maize plants was a major way of N output and its contribution ranged from 68.1% to 99.5% with an average of 80.7%. With increasing mixed ratio of CRN, both N uptake in plant and residual inorganic N in soil showed continuous increased trends and reached the highest values of 234.2 and 108.1 kg·hm^-2 in the CRN30% and CRN45% treatments, respectively, which were 18.0% and 45.1% higher than those in the CRN0% treatment, respectively. Nevertheless, apparent N loss decreased with increasing mixed ratio of CRN, and therefore led to reduced apparent N surplus. The lowest apparent N surplus was 114.4 kg·hm^-2 in the CRN30% treatment, which was reduced by 38.4% compared with the CRN0% treatment. In the treatments with mixed application of CRN, inorganic N contents were higher significantly in topsoil (0-30 cm) but lower in subsoil (60-90 cm) than that in the CRN0% treatment, indicating that less N was leaching down when mixed CRN was applied. The average results throughout two growing seasons showed that: Apparent N recovery rate increased significantly from 50.1% in the CRN0% treatment to 69.4% in the CRN30% treatment, and apparent N residual rate increased significantly with mixed application of CRN, while apparent N loss rate decreased significantly from 37.3% in the CRN0% treatment to 6.0% in the CRN45% treatment. 【Conclusion】 The mixed application CRN and urea is not only conducive to improve grain yield and N uptake of spring maize, but also to maintain a higher soil inorganic N content and reduce N loss, therefore resulting in increased N fertilizer use efficiency. Under the current condition, the appropriate mixed ratio of CRN for spring maize production in Northeast China is around 30% when 185 kg N·hm^-2 is applied.

HORTICULTURE

Molecular Breeding for Flower Colors Modification on Ornamental Plants Based on the Mechanism of Anthocyanins Biosynthesis and Coloration

DAI Si-lan, HONG Yan

Scientia Agricultura Sinica. 2016, 49(3):  529-542.  doi:10.3864/j.issn.0578-1752.2016.03.011

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Flower color, one of the most important quality traits for ornamental plants, is of great adaptive significance during the natural evolution process of plants. Moreover, flower color is also an important content for epigenetic researches. Anthocyanins, the most important pigments for flower coloration, designate the flower colors of approximately 80% plant families in angiosperm. Up to date, more than 400 anthocyanins have been isolated and identified from the natural world, which are mainly derived from six anthocyanidins. The biosynthetic pathway of anthocyanins has been well studied, which starts from the flavonoid metabolic pathway. Different branch pathways result in the diversity of anthocyanins, mainly due to the differences of substituent groups that are located on the basic skeleton of various anthocyanidins. During the biosynthetic process of anthocyanins, the competition forces of enzymes which are located on the branch nodes and the substrate specificity of some key enzymes result in the genus and species specificity of anthocyanins and the corresponding flower color phenotypes. Anthocyanins are transferred to vacuole and are packaged as chromatophore after being biosynthesized. The accumulation and conserve abilities on the chromatophore of vacuole affect the coloration of anthocyanins to a large extent. Therefore, many intracellular factors, such as the pH value of vacuole, the content of co-pigments and the complexation of metal ion, jointly affect the final coloration of anthocyanins in the petals. At present, some structural and regulatory genes that are related to the anthocyanins biosynthesis and coloration have been isolated, whose functions also have been well revealed. Based on these genes, some transgenic flowers have been successfully bred out. However, the mechanisms of gene regulating expression, including the regulation mechanisms on the transcriptional and post-transcriptional levels, and the differences of DNA sequences and the DNA methylation, still remain elusive. Moreover, the present modifications on the flower colors are still very limited. Therefore, how to apply these mechanisms on the transgenic breeding of flower color modification is a frontier topic. Revealing the organ coloration mechanisms based on anthocyanins in horticultural crops is conducive to the understanding of coloration mechanisms of flowers; studies on the mechanisms of flower color in ornamental plants is of important reference value for the reveal of the organ coloration mechanisms in horticultural crops. Therefore, in this paper, we reviewed the mechanisms of flower coloration in ornamental plants from three aspects, including the mechanisms of the branch pathways generation, the genetic regulation mechanisms of anthocyanins biosynthetic pathway, and the main factors affecting the anthocyanins coloration and the corresponding genetic regulation mechanisms. Finally, we summarized the successes of molecular design breeding on flower color modification based on these mechanisms, especially the international-concerned molecular breeding for blue flowers, aiming at providing references for the directive breeding of ornamental plants with novel flower colors.

STORAGE·FRESH-KEEPING·PROCESSING

Analysis of Antioxidative Functional Components from Walnut Green Rind and Its Antioxidation Stability

TIAN Ping-ping, LI Ren-zhou, JIAN Yong-jian, LI Jian-ming, WANG Jie

Scientia Agricultura Sinica. 2016, 49(3):  543-553.  doi:10.3864/j.issn.0578-1752.2016.03.012

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【Objective】This research was conducted to study the analysis and antioxidation stability of antioxidative functional components from walnut green rind (AFCsWGR) which were purified by macroporous resin chromatography, which could provide a theoretical basis for the exploitation and effective utilization of walnut green rinds. 【Method】The crude extract was purified by D101 macroporous resin combined with DPPH free radical scavenging ability, and then concentrated and freeze-dried. Ultra high pressure liquid chromatography high resolution mass spectrometry (UPLC-MS) was used to analyze the AFCsWGR with strong antioxidative activity. The antioxidation stability of AFCsWGR was studied by analyzing the effect of pH, temperature, light, metal ions, oxygenant, reducer and preservative on antioxidation stability.【Result】The results showed that a total of seven antioxidative functional components in walnut green rinds were found, which included chlorogenic acid, brevifolin carboxylic acid, indigo flower- glucose/galactose, ellagic acid, quercetin arabinoside, epicatechin/catechin, quercetin -3-O- glucoside. The results of antioxidation stability of AFCsWGR showed that with the increase of pH value, the DPPH free radical scavenging rate of AFCsWGR decreased. The DPPH free radical scavenging rate was almost zero when the pH value was 12. The DPPH free radical scavenging rate of AFCsWGR could effectively be declined with the extension of storage time. The antioxidant capacity of AFCsWGR was gradually declined under indoor, light and avoiding light treatments, but there was no significant difference among them (P＞0.05). The DPPH free radical scavenging rate of light treatment was lower than the other treatments during 2-5 h. The DPPH free radical scavenging rate of AFCsWGR treated at 4, 37, 70 and 90℃ was presented as a decreasing trend, but with the change trend of increasing first and decreasing thereafter was observed in 50℃ treatment. Fe³⁺ could maintain a higher antioxidant activity of AFCsWGR. However, Al³⁺, K⁺, Cu²⁺ and Mg²⁺ could effectively reduce the antioxidant activity of AFCsWGR. Sodium sulfite solution could reduce antioxidant ability of AFCsWGR. 0.10% and 0.05% H₂O₂ could improve the antioxidant ability of AFCsWGR, thereafter, the antioxidant ability decreased with the increase of the concentration of H₂O_2. Potassium sorbate solution could significantly reduce the antioxidant capacity of AFCsWGR (P＜0.05), which exhibited a negative correlation between the antioxidant capacity of AFCsWGR and the contents of potassium sorbate solution.【Conclusion】The walnut green rind extract had a strong antioxidant activity. The main antioxidative functional components in the walnut green rinds were seven polyphenol active substances. Environmental factors could affect the antioxidation stability of AFCsWGR.:

Effects of Controlled Freezing Point Storage on Aging from Muscle to Meat

LI Pei-di, LI Xin, LI Zheng, CHEN Li, LI Zhong-wen, CHEN Li-juan, TIAN Jian-wen, ZHANG De-quan

Scientia Agricultura Sinica. 2016, 49(3):  554-562.  doi:10.3864/j.issn.0578-1752.2016.03.013

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【Objective】The conversion from muscle to meat after slaughter includes rigor, aging and a series of complicated changes. Temperature is very important for this process and the quality of meat. Aging process also affects meat quality. The objective of this study was to investigate the process of glycolysis in controlled freezing point storage and provide theoretical basis for regulating the speed of aging. 【Method】The longissimus of Poll Dorset rams were stored at controlled freezing point (-1--2℃) and refrigeration (2-4℃) for 9 days. The products of glycolysis and glycolytic activity of key enzyme were analyzed by the corresponding kit. The degradation of myofibrillar protein during post-mortem were analyzed by myofibrillar fragmentation index, combining with the activity of calpain which were analyzed by casein enzyme analysis. 【Result】 The pH value of the refrigeration and controlled freezing point groups were decreased to the minimum value at 3 d and 7 d, respectively, and then increased gradually. The difference of the minimum value of the two groups were not significant. The content of glycogen decreased and then had no significant changes. There were no significant difference between the two groups during post-mortem. The contents of lactic acid were increased and then became stable, followed by degradation, and the lactic acid content of refrigeration was significantly higher than controlled freezing point at 2 h, 6 h, 12 h, 24 h post-mortem. Pyruvate kinase activity reduced before they were stable, and the pyruvate kinase activity of controlled freezing point was significantly higher than refrigeration at 2 h, 24 h post-mortem. Lactate dehydrogenase activity was first increased and then decreased before becoming stable. The lactate dehydrogenase activity of samples in refrigeration was significantly higher than in controlled freezing point storage at 6 h, 12 h, 24 h, 5 d post-mortem. The activity of μ-calpain was increased first and then decreased, μ-calpain activity of controlled freezing point was significantly higher than refrigeration at 12 h, 24 h, 5 d, 7 d post-mortem. Myofibrillar fragmentation index increased gradually, and myofibrillar fragmentation index of refrigeration was significantly higher than controlled freezing point at 6 h, 12 h, 3 d, 5 d, 7 d, 9 d post-mortem.【Conclusion】Compared with refrigeration, there was no significant difference in glycolysis content and minimum pH value between the two groups, but the controlled freezing point delayed the glycogen degradation about 2 d and the lactic acid accumulation about 1 d. Controlled freezing point could impact the decrease of pyruvate kinase activity and the increase of lactic dehydrogenase activity. In addition, controlled freezing point could also weaken the inactivation of μ-calpain. Controlled freeing point could delay glycolysis process about 1-2 days, so it can delay the aging of muscle.

ANIMAL SCIENCE·VETERINARY SCIENCERE

Interference Efficiency of Piwi Gene Expression in the Chicken Germ Stem Cells

LI Zhi-teng, CHANG Guo-bin, XU Lu, MA Teng, CHEN Jing, CHEN Rong, WANG Hong-zhi, LIU Lu, XU Qi, CHEN Guo-hong

Scientia Agricultura Sinica. 2016, 49(3):  563-472.  doi:10.3864/j.issn.0578-1752.2016.03.014

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【Objective】Solving the low transfection efficiency and interference efficiency in poultry stem cell is a big challenge so far. This study was designed to compare the interference effects on Piwi gene expression in chicken primordial germ cells (PGCs) using different ways, aiming to explore effective methods to interfere the poultry stem cells, which is a fundamental work for the study of the self-renewal of stem cell, RNA silencing and post-transcriptional regulation. 【Method】According to the techniques of the separation of primary germ cell, the authors selected 10th and 4th days fertilized eggs post incubation to separate the chicken embryo fibroblast cells(CEF) and germinal ridge, respectively; Herein, the CEF cells were taken as a feeder layer and the PGCs cells were treated by Trypsin-EDTA. The PGCs cells were further identified by the morphology, chemical method and immunology assay. According to the mRNA sequence of chicken Piwi gene published by Genbank (NM_001098852), three positive siRNAs were chemically synthesized and the BLOCK-iT™ Alexa Fluor® Red Fluorescent Oligo was as a negative control. Simultaneously, three interfering vectors of shRNA were constructed using the free carrier of pRNA-U6.1, and an empty vector with GFP fluorophore was as a negative control. Afterwards, the transfection efficiency was detected by the siRNA and shRNA negative control using different types of transfection reagent to optimize the condition, and extracted the RNA of PGCs cells at 24, 48, 72 and 144 h post transfection and analyzed differential expressions of Piwi gene with RT-PCR techniques. All data were analyzed by the SPSS software.【Result】With the premise of well identification of the PGCs cells, siRNA and shRNA were successfully transfected into the cells under the optimized conditions with 50 pmol siRNA and 2 μL Lipofectamine TM 2000 for siRNA transfection group and 500 ng shRNA and 1.5 μL X-Treme GENE HP DNA Transfection Reagent for shRNA transfection group. Compared to the blank group, the Piwi expressions of the negative control had no significant difference at the four time points (24,48,72 and 144 h) in siRNA and shRNA intervention group (P＞0.05); Compared to the negative control and the blank group, Piwi gene expressions were significantly down-regulated in experimental groups at the first three time points in siRNA intervention group, while were significantly down-regulated at all of time points in the shRNA intervention group (P＜0.05).【Conclusion】Collectively, the interference effects on Piwi gene expression in chicken PGCs were compared by siRNA and shRNA RNAi technology, and indicated that the shRNA vector had higher and more stable interference efficiency, which help to provide some basic information for future research of RNAi technology.

Investigation and Analysis of Main AFN in Soybean Meal and Fermented Soybean Meal

YANG Yu-juan, YAO Yi-sha, QIN Yu-chang, QIU Jing, LI Jun-guo, LI Jun, GU Xu

Scientia Agricultura Sinica. 2016, 49(3):  573-580.  doi:10.3864/j.issn.0578-1752.2016.03.015

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【Objective】Soybean meal is the main raw material of feed. However, various anti-nutritional factors (ANF) in soybean meal hinder the digestion, absorption and utilization for nutrients, which would have negative effects on animal growth and health. Studies have shown that soybean meal fermented by microorganism could decrease the undesirable effect of ANF. While, fermentation strains, soybean species, and manufacturers may have an effect in fermentation process. Moreover, seldom reports referred to the levels of ANF in soybean meal and fermented soybean meal. Based on this, 65 batches of available soybean meal and 54 batches of fermented soybean meal were collected in this study, followed by analysis of 6 kinds of ANF, including glycinin, β-conglycinin, trypsin inhibitors, raffinose, stachyose and urease, in order to investigate the actual levels of ANF in soybean meal and fermented soybean meal.【Method】In this study, glycinin, β-conglycinin and trypsin inhibitors were analyzed by Enzyme-link Immunosorbent Assay (ELISA) method. Experimental procedures were conducted according to instructions which were sample pretreatment, plus, washing, adding enzymatic reagent, color reaction, and termination. The analysis method of raffinose and stachyose was HPLC after extracted by microwave. Analysis of urease refers to GB/T 8622-2006, and titration was utilized for analysis of urease activity.【Result】The average concentration of glycinin in soybean meal (129.3 mg·g^-1) is 57.7% higher than fermented soybean meal (54.7 mg·g^-1). The percentile method was used for analysis. The normal values in soybean meal and fermented soybean were 58.9-177.3 mg·g^-1 and ND (Not Detected)-109.4 mg·g^-1, respectively. Moreover, the fermented soybean meal (37.6 mg·g^-1) is 63.2% lower than the concentration of β-conglycinin in soybean meal (102.2 mg·g^-1). The normal values in soybean meal and fermented soybean were 42.8-147.2 mg·g^-1 and ND-61.8 mg·g^-1, respectively. The average concentration of trypsin inhibitors in soybean meal (18.4 mg·g^-1) is 59.1% higher than fermented soybean meal (7.5 mg·g^-1). In addition, the normal values of trypsin inhibitor in soybean meal and fermented soybean meal were ND-28.9 mg·g^-1 and ND-9.9 mg·g^-1. The average concentration of raffinose in soybean meal and fermented soybean meal were 11.02 mg·g^-1 and 1.93 mg·g^-1, with the former is 80% higher. The normal values of raffinose in soybean meal and fermented soybean meal were ND-13.79 mg·g^-1 and ND-4.65 mg·g^-1. The average value of stachyose average in soybean meal (29.70 mg·g^-1) is higher than in fermented soybean meal (5.19 mg·g^-1). The normal values of stachyose are ND-33.29 mg·g^-1, ND-11.58 mg·g^-1, respectively. The normal values of urease in soybean meal was in the range of ND to 0.40 U·g^-1, while the activity value of urease of fermented soybean meal was under the detection limit.  It was concluded that the concentrations of ANF in fermented soybean meal have decreased differently compared with soybean meal.【Conclusion】This research provided data support for further optimization of feed processing, and could act as a guide for breeding companies to choose higher quality of soybean meal and fermented soybean meal as feed raw materials.

ANIMAL SCIENCE·VETERINARY SCIENCERE·SOURCE INSECT

Bac-to-Bac Baculovirus System Facilitates Overexpression of let-7 Cluster MicroRNAs of Silkworm (Bombyx mori)

HE Ting, YIN Quan, WANG Wei, HUANG Ya-xi, WU Xiao-yan, XIA Qing-you, LIU Shi-ping

Scientia Agricultura Sinica. 2016, 49(3):  581-592.  doi:10.3864/j.issn.0578-1752.2016.03.016

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【Objective】The objective of this study is to construct the Bac-to-Bac baculovirus system overexpressing bmo-let-7, bmo-miR-100, bmo-miR-2795 of bmo-let-7 cluster (bmo-let-7-C), as such will hopefully contribute the future functional study of microRNAs (miRNAs) in the silkworm (Bombyx mori).【Method】The primary precursor of each microRNA in the bmo-let-7-C (pri-let-7, pri-miR-100, pri-miR-2795) and the whole let-7-C sequence were cloned, respectively. Using the gene of red fluorescent protein (RFP) as the reporter and pFastBac1 as the shuttle vector, each cloned miRNA precursor and reporter gene were combined into the baculovirus genome through Tn7 transposons, and thus the recombinant baculovirus plasmids (rBacmids) for each miRNA and the whole cluster were obtained. At 72 h post transfection of these recombinant Bacmids into the cell line of Spodoptera frugiperda (Sf9), the signal of red fluorescent protein was examined under the microscope and the expression of miRNA was evaluated by qRT-PCR. To collect the recombinant baculovirus with infection activity, the Sf9 cell culture was centrifuged at 72 h post transfection, and the supernatant containing the viruses was used to infect the newly cultured Sf9 cells or injected into early 5th instar larval B. mori. Also, the signal of red fluorescent protein and the expression of miRNA were examined.【Result】The primary precursor of each miRNA and the whole let-7-C sequence were successfully combined into the baculovirus genome and the overexpressing vectors for each miRNA and the whole cluster were finally obtained. At 72 h post transfection in the Sf9 cell line, a red fluorescent protein was observed under the microscope and the overexpression of microRNAs were confirmed by qRT-PCR. The recombinant baculovirus with infection activity caused the stronger detection signals of red fluorescent protein and significant overexpression of each miRNA in the newly cultured Sf9 cell. After the injection of recombinant baculovirus into newly ecdysed 5th instar larvae of the B. mori, the infection of virus in various B. mori tissues was determined by real-time PCR and bmo-let-7, bmo-miR-100, and bmo-miR-2795 showed significant up-regulation in the B. mori injected with each Bac-miRNA, but only bmo-miR-2795 was dramatically overexpressed in the B. mori infected with Bac-let-7-C. Further examination revealed the tissue-specific infection of the recombinant baculoviruses and the significant overexpression of miR-2795 was confirmed in the hemocyte, midgut, and fat body.【Conclusion】The baculovirus expression system was successfully used to overexpress the cluster miRNAs of B. mori in the cell line of S. frugiperda (Sf9) and in the larval B. mori body, and might be helpful to the mechanical and functional exploration of let-7 cluster and other miRNAs in this species.

RESEARCH NOTES

Genetic Diversity and Population Structure Analysis of Main Sweet Potato Breeding Parents in Southwest China

LUO Kai, LU Hui-xiang, WU Zheng-dan, WU Xue-li, YIN Wang, TANG Dao-bin, WANG Ji-chun, ZHANG Kai

Scientia Agricultura Sinica. 2016, 49(3):  593-608.  doi:10.3864/j.issn.0578-1752.2016.03.017

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【Objective】 To provide a reference for the conservation and application of breeding parentallines resource, as well as molecular assistant selection (MAS) in sweet potato (Ipomoea batatas), a comprehensive analysis of genetic diversity and population structure analysis of the main sweetpotato breeding parentallines in southwest China was performed. 【Method】 Genetic diversity of 82 main sweet potato breeding parents in southwest China was evaluated by using 61 sample sequence repeats (SSR) markers, 13 agronomic traits and 6 quality traits. The Nei72 genetic distance matrices of 82 tested sweet potato breeding parents were generated based on SSR markers while quality trait and agronomy trait were assessed using NTSYS-pc version 2.10. The mean genetic distance of the tested sweet potato breeding parents based on SSR marker, quality trait and agronomy trait were generated by using Mega version 6.06. Mantel test among genetic distance matrices generated based on SSR marker, quality trait and agronomic trait were conducted by using NTSYS-pc version 2.10. The unweighted pair group method with arithmetic mean (UPGMA) cluster analysis of 82 sweetpotato breeding parents based on quality trait, Neighbor-Joining (NJ) cluster analysis based on SSR marker and UPGMA cluster analysis based on agronomy trait were performed by using Mega version 6.06. Meanwhile, the population structure of 82 sweet potato genotypes was determined based on polymeric data generated by SSR markers using STRUCTURE version 2.4.【Result】 405 polymorphic loci were detected using 61 SSR markers with a mean of 6.64 alleles per primer pair. The number of polymorphic loci obtained from each primer pair ranged from 1 to 17. The SSR marker, quality trait and agronomic trait-based mean Nei’s genetic diversity of tested sweet potato breeding parents was 0.35, 0.22 and 0.03, respectively The tested 82 sweet potato genotypes could be divided into 7 subgroups based on NJ clustering using SSR markers. This same sweet potato collection could be divided into 1 major subgroup and 3 minor subgroups based on UPGMA method using either agronomic or quality traits, but the results showed differentiation. Among the tested sweet potato breeding parents, the genotypes with different original resources could be clustered into the same subgroups in the cluster analysis based on SSR marker, quality trait and agronomic trait, indicating there was no significant genetic differentiation among the tested sweet potato genotypes from different original resources. Mantel test detected little correlation among genetic distance matrices generated by using SSR marker, quality trait and agronomic trait (r=0.016), and a negative correlation (r=-0.041) was detected between genetic distance matrices generated by using quality and agronomic trait. The maximum ad hoc quantity ΔK was observed for K=3 in population structure analysis, indicating that the entire collection could be divided into three subpopulations. Using a membership probability threshold of ≥0.60, 53 genotypes (accounting for 64.6% of the tested genotypes) were assigned to the three subpopulations, and 29 (account for 35.4% of tested breeding parents) were retained in the admixed group (AD). The assignment of 82 sweetpotato genotypes determined by structure analysis was similar but not fully consistent with the assignment pattern of NJ clustering based on SSR marker. 【Conclusion】 Our results demonstrated that a wide genetic diversity at the genomic level was found among the tested main sweet potato breeding parental lines in southwest China. Genetic differentiation could be found in their quality traits, but little differentiation could be found in their agronomic traits. Furthermore, there exists a strong limitation in studying genetic diversity by using a single marker system or trait, and comprehensive analysis systems, combining molecular markers and various phenotypic traits should be given priority in further studies of genetic relationships and population structure of sweet potato breeding parental lines.