Table of Content

12 January 2014, Volume 40 Issue 01

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genome-wide Association Analysis of Kernel Row Number in Maize

ZHANG Huan-Xin,WENG Jian-Feng,ZHANG Xiao-Cong,LIU Chang-Lin,YONG Hong-Jun,HAO Zhuan-Fang,LI Xin-Hai

Acta Agron Sin. 2014, 40(01):  1-6.  doi:10.3724/SP.J.1006.2014.00001

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Kernel row number (KRN) is one of grain yield components in maize (Zea mays L.). Investigation of its genetic architecture will help develop high-yield varieties in maize. In this study, the KRN in a panel of 203 maize inbred lines was detected in Urumqi of Xinjiang, Gongzhuling of Jilin, and Sanya of Hainan in 2007, and used to perform the genome-wide analysis for KRN using MaizeSNP50 BeadChip. A total of nine SNPs were found to be significantly associated with KRN at a threshold of P < 0.0001, which were on chromosome Bins 1.02, 1.10, 7.03, 8.02, 9.06, and 10.03, respectively. Eight of these SNPs were located in the QTL intervals reported previously.Meanwhile, four candidate genes were scanned, encoding auxin signaling F-box containing protein, kn1 protein, AP2 domain containing protein and leucine-rich repeat transmembrane protein kinase respectively. In summary, these identified genes and SNPs will offer essential information for cloning yield-related genes in maize.

Correlation and Association Analysis between Biomass and Yield Components in Soybean

CHAO Mao-Ni,HAO De-Rong,YIN Zhi-Tong3,ZHANG Jin-Yu,SONG Hai-Na,ZHANG Huai-Ren,CHU Shan-Shan,ZHANG Guo-Zheng,YU De-Yue

Acta Agron Sin. 2014, 40(01):  7-16.  doi:10.3724/SP.J.1006.2014.00007

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Biomass, one of the main factors that determine the effective economic yield, has an important effect on the final seed yield. In this study, a genome-wide association analysis was conducted to detect key single-nucleotide polymorphisms (SNPs) associated with biomass and yield components using 1142 SNPs in a soybean landraces panel. There existed abundant phenotypic and genetic diversities and significant correlations among biomass and yield components in the population, and the correlation between biomass and seed yield was slightly higher than that between biomass and seed weight. Genome-wide association analysis using a mixed linear model detected 41, 56, and 29 SNPs associated with biomass, seed weight and seed yield respectively. Among them, 6, 19, and 1 SNPs were detected in two environments. In addition, 15 SNPs were found co-associated with two or more different traits and BARC-029051-06057 on chromosome 19 was associated with the three traits, which implies a partially common genetic basis for the three traits. Many SNPs detected in our study were found co-associated with soybean chlorophyll, chlorophyll fluorescence parameters and yield components in our previous study. The identification of these significant SNPs will be helpful to better understand the genetic basis of biomass and yield components, and facilitate the pyramiding of favorable alleles for future high-yield breeding by marker-assisted selection in soybean.

Analysis of Association of puroindoline b-2 Alleles with Yield-Related Traits in Bread Wheat

CHEN Feng,LI Xiang-Nan,CAO Ying-Ying,SUN Jian-Xi,ZHANG Fu-Yan,DONG Zhong-Dong,CUI Dang-Qun

Acta Agron Sin. 2014, 40(01):  17-21.  doi:10.3724/SP.J.1006.2014.00017

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puroindoline b-2 (Pinb-2) genes were recently discovered and possess high similarity with puroindoline b gene. We have identified several Pinb-2 alleles in B genome of bread wheat (Triticum aestivum L.) and found association between allelic variation on Pinb-2 and grain texture in soft wheat. In this study, we analyzed the association between the Pinb-2 alleles and yield-related traits and flag leaf size, and mapped the Pinb-2 locus using a recombinant inbred line (F₈) population. Among the four Pinb-2 genotypes, Pinb-2v3b genotype possessed the highest 1000-grain weight, grain diameter, grain number per spike, grain weight per spike, and grain weight per plant. Therefore, Pinb-2v3b genotype possibly has more preferable yield-related traits than Pinb-2v2, Pinb-2v3a, and Pinb-2v3c genotypes. Additionally, Pinb-2v3a genotype possessed the highest flag leaf width, length, and area. Genetic mapping indicated that Pinb-2 was located on the long arm of chromosome 7B close to SSR marker Barc315. This result provides basic information for use of puroindoline b-2 genes in molecular genetics research and breeding.

Development and Characterization of AcAMP-sn Transgenic Wheat with Enhanced Resistance to Wheat Take-all

YANG Kun,LIU Xin,DU Li-Pu,YE Xing-Guo,ZHANG Zeng-Yan

Acta Agron Sin. 2014, 40(01):  22-28.  doi:10.3724/SP.J.1006.2014.00022

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Antimicrobial peptides, small molecular weight proteins with broad spectrum antimicrobial activity, play important roles in plant defense responses. The open-reading-frame sequence of AcAMP-sn was synthesized and used to construct the gene transformation vector pAHC25::AcAMP-sn, in which AcAMP-sn gene was driven by maize ubiquitin promoter and should be highly expressed in monocot plants. The vector pAHC25::AcAMP-sn DNA was introduced into Yangmai 18 via particle bombardment. AcAMP-sn transgenic wheat plants were subjected to PCR, semi-RT-PCR, Q-RT-PCR analyses, and disease response assessments. PCR analyses revealed that theintroducedgene AcAMP-sn could be stably inherited in five transgenic wheat lines from T₀ to T₄ generations. Semi-RT-PCR and Q-RT-PCR analyses showed that the AcAMP-sn gene was highly expressed in transgenic wheat lines compared with untransformed Yangmai 18. Based on disease response assessments for T₄ generations, the significantly enhanced-resistance to take-all accompanied with decreased fungal abundance, in the five independent AcAMP-sn transgenic lines. Over-expression of AcAMP-sn gene in transgenic wheat plants confers increased resistance to wheat take-all.

Cloning a Novel Gene TaNRX of Trx Superfamily and Developing Its Molecular Markers Related to Drought Resistance in Common Wheat

ZHANG Fan,JIANG Lei,JU Li-Ping,JIN Xiu-Feng,WANG Xuan,ZHANG Xiao-Ke,WANG Hong-Li,FU Xiao-Jie

Acta Agron Sin. 2014, 40(01):  29-36.  doi:10.3724/SP.J.1006.2014.00029

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Molecular markers associated with genes for drought resistance play an important role in wheat breeding aiming at improvement of drought resistance. In this study, we obtained the full-length cDNA of a novel gene of thioredoxin (Trx) superfamily, TaNRX (GenBank accession number KC890769), from common wheat (Triticum aestivumresidues with a putative molecular mass of 63.79 kD. The TaNRX is composed of three Trx-like modules arranged as direct repeats of the classic Trx domain. The first and third modules contain the amino acid sequence Cys-X1-X2-Cys, with the potential for Trx oxidoreductase activity. Gene TaNRXcomplementary dominant markers were developed. In 150 wheat varieties (lines), two genotypes on TaNRX locus, TaNRX-a and TaNRX-b, were identified to be associated with drought resistance. As revealed by the four molecular markers, the average RGer in TaNRX-a genotype was significantly higher than that in TaNRX-b genotype (P < 0.01). This result suggests that the molecular markers developed in this study are effective to be used in selection of wheat varieties with drought resistance. has four exons and three introns, and is mapped on chromosome 5BS of wheat. The variations of TaNRX sequences were mainly concentrated in the first intron according to genomic sequence variances analysis between two types of varieties with different relative germination rates (RGer). Based on the variations within the first intron of TaNRX, four L.) using the protocol of gene homology cloning, electronic cloning, RACE, and bioinformatics analysis. The open reading frame (ORF) of TaNRX is 1734 bp in length, and the 5′ and 3′ UTRs are 99 and 182 bp, respectively. The ORF encodes a protein of 577 amino acid

Epistatic Effects and QTL×Environment Interaction Effects of QTLs for Yield and Agronomic Traits in Soybean

LIANG Hui-Zhen,YU Yong-Liang,YANG Hong-Qi,ZHANG Hai-Yang,DONG Wei,LI Cai-Yun,GONG Peng-Tao,LIU Xue-Yi,FANG Xuan-Jun

Acta Agron Sin. 2014, 40(01):  37-44.  doi:10.3724/SP.J.1006.2014.00037

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Improving seed yield is an important goal of soybean breeding programs. In this investigation, a soybean SSR genetic linkage map constructed by a total of 447 recombinant inbred lines (RILs) derived from a cross between Jindou 23 (cultivar, female parent) and ZDD2315 (semi-wild, male parent) and the mixed linear model was used to identify the QTLs of yield and other QTLs for major agronomic traits in a two-year experiment. Nine QTLs bearing additive effects for pod position, plant height, node number on main stem, branch number, stem thickness and yield per plot were mapped in the linkage groups J_2, I, and M. The QTLs of yield per plot, stem thickness, plant height, branch number and node number on main stem showed positive additive effects donated by Jindou 23. Seven pairs of epistatic effects QTLs for pod position, plant height and stem thickness were detected, which had an interaction with environments. The results indicated that the epistatic effects and the environmental factors played an important role in yield per plot and agronomic traits in soybean. It will be very important to pay attention to not only QTLs with major effects but also those with epistatic effects in soybean molecular marker-assisted breeding in considering the stability expression and inheritance of the agronomic traits.

Molecular Cloning and Expression Analysis of FAD2 Gene from Three Wild Potato Species with Different levels of Freezing Tolerance

LI Fei,XU Jian-Fei,LIU Jie,DUAN Shao-Guang,BIAN Chun-Song,Jiwan P. PALTA,JIN Li-Ping

Acta Agron Sin. 2014, 40(01):  45-53.  doi:10.3724/SP.J.1006.2014.00045

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Using reverse transcription polymerase chain reaction (RT-PCR), three new full-length cDNAs of ω-6 desturases (FAD2) were obtained from three wild potatospecies with different levels of freezing tolerance and cold acclimation capacity, Solanum commersonii, S. acaule,and S. cardiophyllum, designated Cmm-FAD2 (GenBank accession No. KF214782), Aca-FAD2 (KF214781), and Cph-FAD2 (KF214783). Theresults of sequence analysis indicated that their nucleotide length is all 1326 bp, coding 441 amino acids. It’s detected that eight nucleotides resulted in corresponding change of amino acids among the eighteen difference nucleotides by nucleotide and protein sequences alignment of FAD2 genes from three potato species. At the amino acid residue 11 and 44, sequencesof S. commersonii and S. acaule are different from that of S. cardiophyllum. The results of secondary structure prediction indicated that there are obvious differences in alpha-helix, extend chain and random crimp of S. commersonii and S. acaule as compared with S. cardiophyllum. By protein multiple sequence alignments and phylogenetic tree analyses, the results showed that FAD2 genes from three species are highly similar to these of tomato and purslane. The results of qPCR showed that FAD2 genes expression was up-regulated in the three potato wild species, there existed significant differencein relative expression level of FAD2

Identification, Genetic Analysis and Gene Mapping of a Rice Blast Resistance Gene in Japonica Rice

LI Bin,DENG Yuan-Bao,YAN Xue-Hai,YANG Yang,LIU Peng-Qiang,DU Yong,XIE Pei,WANG De-Zheng,DENG Qi-Ming,LI Ping

Acta Agron Sin. 2014, 40(01):  54-62.  doi:10.3724/SP.J.1006.2014.00054

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7001S is a male-sterile rice with broad-spectrum resistance to rice blast pathogens and highly resistant to 22 strains of Magnaporthe oryzae (M. oryzae). The F₂ generation of hybrid between 7001S and 80-4B showed significant resistance to rice blast pathogens. The ratio of resistant plants: susceptible plants was 3:1, indicating that the resistance of 7001S to the rice blast is controlled by one-dominant karyogene or a QTL locus. Molecular marker analysis showed that the rice blast resistance gene was located on the terminal long arm of chromosome 11 between P21-2415 and RM27322, with genetic distance of 0.27 cM and physical distance of 310 kb. Some co-segregated molecular markers were also found in this gene area and could be used for identifying candidate genes.

Improvement of Minimal Gene Cassette Expression Stability by Scaffold Attachment Region (SAR) Sequence in Wheat Transformation

SU Rui-Bo,CHEN Ming,XU Zhao-Shi,LI Lian-Cheng,MA Qing,MA You-Zhi

Acta Agron Sin. 2014, 40(01):  63-71.  doi:10.3724/SP.J.1006.2014.00063

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The minimal expression cassette only containing the promoter, coding sequence and terminator sequence is transformed into plants genome, which will reduce the security risks that may be caused by the vector skeleton sequence. Scaffold attachment region (SAR) combining with the nuclear matrix to separate transformed DNA fragment with adjacent genome sequence, which block the influence of the neighboring chromatins and improve the stability of exogenous gene. In this research, a new vector was constructed with the minimal expression cassette flanked with SAR sequences. This vector was used in wheat transformation by micro-particle bombardment aiming at improving stability of exogenous gene expression. GUS as a reporter gene was constructed in the minimal expression cassette flanked with SAR sequences, and this DNA fragment was transformed into what variety Kenong 199. At same time, the fragment with the minimal expression cassette but without the SAR was used as a control. A total of 857 immature embryos were bombarded using the minimal expression cassette with GUS and SAR sequences, and 40 T₀ plants were obtained, of which 16 plants were positive by PCR testing and 15 plants were positive by GUS staining. The transformation efficiency was 1.87%. In the 18 individuals randomly selected from the T₁ generation derived from four positive T₀ plants, 15 plants showed positive reactions in PCR testing and GUS staining. In contrast, transformation efficiency of the control was only 0.49% (five PCR positive plants/1012 immature embryos), and only two PCR positive plants were confirmed by GUS staining. In 10 T₁ plants of the control derived from five T₀ PCR positive lines, no positive plant was identified by either PCR assay or GUS staining. Using this improved method, a new drought-related transcription factor gene GmDREB3 from soybean was transformed into wheat receptor Jimai 22. A total of 130 T₀ plants were obtained from 6045 immature embryos bombarded, of which 30 plants were positive by PCR testing with transformation efficiency of 0.50%. Six positive plants were randomly selected for expression analysis, and five showed GmDREB3 expression by RT-PCR assay. Integrality of inserted fragment in transgenic wheat genome was further identified in the five plants by PCR assay, and four transgenic plants had amplified products similar to the fragment transformed. Real-time PCR results showed 1–3 copies of GmDREB3 genes in the six positive T₀ plants. These results indicate that the transformation stability is significantly improved by adding SAR sequences flanked with the minimal expression cassette.

Statistical Genetics Approach for Functional Difference Identification of Allelic Variations and Its Application

HU Wen-Ming,KAN Hai-Hua,WANG Wei,XU Chen-Wu

Acta Agron Sin. 2014, 40(01):  72-79.  doi:10.3724/SP.J.1006.2014.00072

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Allelic variations are ubiquitous in organisms, and play important roles in regulating genes expression. In order to study the influence of number of varieties (A), average polymorphism information content (B) and total contribution of candidate genes (C) on the association analysis of candidate genes, the empirical Bayes (E-Bayes) method was applied to explore the effects of abovementioned three factors on the statistical power of candidate genes, the accuracy and precision of the estimates of genetic effects and the false discovery rate (FDR). Results were as follows: (1) With the increase of factors A, B, and C, the statistical power and the accuracy and precision of the estimates of genetic effects were all enhanced, meanwhile the FDR was decreased; (2) Factor B had a significant influence on the statistical power of candidate genes. When factor B was at a higher level, the averaged statistical power could still reach 80% even though both factors A and C remained at lower levels. When factor B was at a medium level, more varieties were needed to ensure that the statistical power could reach 80%. However, when factor B was at a lower level, even though factor A was equal to 100, the statistical power in three different levels of factor C could not reach 50%; (3) Factor B had a significant impact on the accuracy and precision of estimated effects of candidate genes. With the increase of factor B, both the accuracy and precision of effect estimates for candidate genes were improved simultaneously; (4) Factor B also had an important effect on FDR. Through a real data analysis in rice, four detected candidate genes were significantly associated with pasting temperature (PT) by our model. Therefore, the polymorphism information content is a primary factor for detecting the functional difference of alleles. In addition, more varieties and higher contribution rate also have important influence on the statistical power and the accuracy and precision of estimates of effects.

Characterization of Micorsatellites in Tea (Camellia sinensis) Floral Transcriptome

WANG Li-Yuan,WEI Kang,ZHANG Cheng-Cai,CHENG Hao

Acta Agron Sin. 2014, 40(01):  80-85.  doi:10.3724/SP.J.1006.2014.00080

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The microsatellites or simple sequence repeats (SSRs) in Camellia sinensis floral transcriptome were characterized. A total of 12 582 SSRs were identified in 10 290 unigenes, with one SSR per 2.41 kb. Among all 340 SSR motifs,(AG/CT)n was the most frequent repeat motif (44.99%). A total of 10 409 SSRs occurred in 49586 unigenes with Blast matches to annotated proteins in four databases, only 1 917 of which occurred in protein-coding regions of these sequences. The density of SSRs was much higher in non-coding regions than in coding regions (0.102 SSRs per 1000 base pairs in coding regions vs. 3.072 in non-coding regions). In the six repeat motifs, tri-nucleotide repeats were the most abundant in coding regions (1140), followed by hexa-nucleotide (524) repeats. The microsatellites with length below 20 bp were in maximum proportion, while the microsatellites over 20 bp were only 25.22%. The expression level of genes containing microsatellites was significantly lower than that not containing microsatellites. The overall expression levels of genes containing compound microsatellites were lowest.

Production of Very Long Chain Polyunsaturated Fatty Acids in Cotton

LIU Jiang,MA Yan-Bin,SUN Quan-Xi,WU Xia,LI Xue-Ying,SUN Mei-Hong,LI Yan-E,LI Xin-Zheng,QI Bao-Xiu

Acta Agron Sin. 2014, 40(01):  86-92.  doi:10.3724/SP.J.1006.2014.00086

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We have isolated four genes encoding a Δ9 elongase, a Δ8 desaturase, a Δ5 desaturase, and a Δ15 desaturase from Isochrysis galbana, Euglena gracilis, Mortierella alpina and Arabidopsis thaliana respectively. Using a multigene transfer technology that we developed, these genes were stacked together in the plant expression vector pCambia2300. Each gene contained its own CaMV35S promoter and Tnos terminator.This plant expression vector was then transferred into cotton by Agrobacterium-mediated transformation method. Transgenic cotton seedlings were first identified by screening them based on kanamycin-containing media and followed by PCR with gene-specific primers of the four transgenes. Finally, these transgenic plants were subjected to gas liquid chromatography analysis for their fatty acid composition and the results showed that the contents of arachidonic acid (ARA, 20:4Δ^5,8,11,14) and eicosapentaenoic acid (EPA, 20:5Δ^5,8,11,14,17) were 1.0% and 5.0% respectively in the leaves of the transgenic plants, indicating that the four genes were expressed incotton. Therefore, our data clearly demonstrated the feasibility for the heterologous production of EPA in cotton and this will lay a foundation for the production of VLCPUFAs, including EPA and DHA in cotton seed through transgenic technology in the future.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Nitrogen Fertilizer Management on Yield and Nitrogen Use Efficiency in Winter Wheat Growing on Dryland with Plastic Film Mulching

LI Qiang,WANG Zhao-Hui,LI Fu-Cui,DAI Jian,LI Meng-Hua,HE Gang,CAO Qun-Hu, DUAN Chang-Lin,YU Chang-We

Acta Agron Sin. 2014, 40(01):  93-100.  doi:10.3724/SP.J.1006.2014.00093

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Wheat production in Northwest China is mainly restricted by insufficient and uneven distributed precipitation across seasons. Besides, luxurious and improper application of nitrogen (N) is an obvious problem. In a two-year field experiment from October 2010 to June 2012, we compared grain yield and N use efficiency of winter wheat with cultivation patterns of conventional fertilization (P), current farmer’s habitual fertilization (C), reducing N with early-spring topdressing (NT), NT + ridging and mulching with plastic film (NR), and NR+ high plant density (NRH). Compared with P treatment, C had no effect on stable increases of grain yield and N use efficiency, while NT, NR, and NRH treatments significantly increased yield and N use efficiency of wheat. However, N content in grain was reduced in NR and NRH treatments. In an overall view, NR was the optimal treatment for high-yield and high-efficient wheat production, with the increases of grain yield, N partial factor productivity, and N physiological efficiency by 38.6%, 49.6%, and 35.1% in the first cropping year and by 7.6%, 16.3%, and 25.7% in the second year, respectively. These results indicate that N management plus ridge mulching is an important technique for high-yield production in Northwest China, and suitable N supply after flowering should be considered for high quality also.

Effects of Ridging with Mulching on Yield and Water Use Efficiency in Winter Wheat in Semihumid Drought-Prone Region in China

HAN Juan,LIAO Yun-Cheng,JIA Zhi-Kuan,HAN Qing-Fang,DING Rui-Xia

Acta Agron Sin. 2014, 40(01):  101-109.  doi:10.3724/SP.J.1006.2014.00101

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The objective of this study was to explore the effects of the ridge and mulch on soil moisture, grain yield, and water use efficiency (WUE) in rainfall winter wheat growing region in Weibei Area. In a three-year field experiment from Sept. 2007 to June 2010, we compared three ridge (for collecting rainfall) and mulch treatments with traditional plat planting as the control (CK). The ridge was covered with common plastic film, and the dent was bare (P1) or covered with either wheat straw (P2) or degradable film (P3). At the early growth stage of winter wheat, soil water storages in 0–20 cm and 20–100 cm layers were significantly higher in all ridge and mulch treatments than in CK, particularly in P2. At late growth stage, the effect of P3 was similar to that of P1 with no significant difference due to the degradation of the film in dent. However, compared to CK, treatments P1, P2, and P3 had no effect on soil water storage in 100–200 cm layer. Plant height and biomass of wheat were the largest in P2, which were 26.68% and 60.28% higher than that of CK, respectively. Moreover, P2 was also the best treatment for grain yield and WUE with 39.29% increased yield and 35.57% increased WUE over CK. Yield and WUE were similar between P3 and P1 with no significant difference. Therefore, P2 is recommended as an efficient planting pattern in semi-humid drought-prone wheat region.

Identification and Classification of Sorghum Cultivars for Drought Resistance during Germination Stage Based on Principal Components Analysis and Self Organizing Map Cluster Analysis

WANG Yi-Tao,ZHOU Yu-Fei,LI Feng-Xian,YI Bing,BAI Wei,YAN Tong,XU Wen-Juan,GAO Ming-Chao,HUANG Rui-Dong

Acta Agron Sin. 2014, 40(01):  110-121.  doi:10.3724/SP.J.1006.2014.00110

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PEG-6000 was used to simulate drought stress environmentin artificial climate chamber for studying the effects of different concentrations of PEG-6000 (80, 120, 150, and 175 g L^–1) on the response of 31 sorghum cultivars at germination stage, with the objectives of screening drought-resistant cultivars and exploring methods suitable for assessing drought-resistance of sorghum cultivars. Through principal component analysis (PCA) and Self-Organizing-Map (SOM) cluster analysis, the drought-resistance of 31 sorghum cultivars was evaluated. PCA showed that relative bud length, relative root length and drought-resistance index during germination had the maximum weight in values, and were used as the main indices for evaluating and ranking the drought-resistant capabilities of 31 sorghum cultivars. Five groups of drought-resistance capabilities of 31 sorghum cultivars were detected based on SOM cluster analysis: four cultivars including Jiza305 were highly drought-resistant, four cultivars including HL8 were drought-resistant, eight cultivars including Liaoza 10 were medium drought-resistant, seven cultivars including Jinza 103 were drought-sensitive and eight cultivars including Jinza93 were highly drought-sensitive. In conclusion, relative bud length, relative root length and germination drought-resistance index can be used as indices for identifying drought-resistance in sorghum, and SOM cluster analysis is an important method for classifying drought-resistance.

Effect of Planting Density on Yield and Photosynthate Production Characteristics in Different Types of Rice with Bowl Mechanical-Transplanting Method

ZHU Cong-Cong,ZHANG Hong-Cheng,GUO Bao-Wei,CAO Li-Qiang,JIANG Feng,GE Meng-Jie1,HUA Jin1,SONG Yun-Sheng,ZHOU Xing-Tao,HUO Zhong-Yang,XU Ke,Dai Qi-Gen,WEI Hai-Yan,ZHU Da-Wei

Acta Agron Sin. 2014, 40(01):  122-133.  doi:10.3724/SP.J.1006.2014.00122

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 In order to study the impacts of planting density of nutrition bowl seedling mechanical-transplanting rice on photosynthate production and yield, a field experiment was conducted using conventional japonica rice Nanjing 44, Wuyunjing 24, japonica hybrid rice Yongyou 8, Changyou 5, and indica hybrid rice Liangyoupeijiu, II you 084 which have been widely grown in the southern China with high, medium and low density treatments of the different hill spacings in nutrition bowl mechanical-transplanting (12 cm, 14 cm, and 16 cm), and the conventional blanket seedling mechanical- transplanting as control. The results showed that, the tiller number of nutrition bowl mechanical-transplanting rice in the critical period and the declining rate of leaf area after heading decreased with the reduction of planting density, the productive tiller percentage increased significantly, while the chlorophyll content of flag leaf and the photosynthetic parameters presented the opposite trend. The dry matter weight of single stem, the matter transportation amount in stem and leaf, and the net assimilation rate were all the highest in the low density treatment, the medium in medium density treatment, and the lowest in high density treatment. After heading, the dry matter accumulation, population growth rate, photosynthetic potential and other indicators of conventional japonica rice decreased significantly with the reduction of planting density. The average dry matter weight of population in high density treatment at maturity stage was 11.8% and 8.9% higher than that in medium density treatment and low density treatment respectively, and without significant difference between the low density treatment and control. For the population growth indexes of hybrid rice, medium density treatment was the highest, and there was no significant difference between high density treatment and low density treatments. The actual yield in high density treatment was between that in medium and low density treatments, besides, that in high density treatment of indica hybrid rice was equal to that in low density treatment, but significantly lower than that in medium density treatment by 3.0%. Consequently, for conventional japonica rice and varieties with big panicle and numerous grain in agricultural production, the hill spacing of 12 centimeters could reach high yield, while for hybrid rice and big heavy panicle varieties, increasing the hill spacing appropriately was helpful to improve the percentage of spike-forming tillers and develop the advantage of panicle type, resalting in high yielding and high efficiency production.

Yield Component and Dry Matter Accumulation in Wheat Varieties with 9000 kg ha⁻¹ Yield Potential in Sichuan Basin

TANG Yong-Lu,LI Chao-Su,WU Chun,WU Xiao-Li,HUANG Gang,HE Gang

Acta Agron Sin. 2014, 40(01):  134-142.  doi:10.3724/SP.J.1006.2014.00134

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The objective of this study was to explore yield-forming characteristics of super-high-yield (SHY) wheat varieties that grow under high temperature, high humidity, and weak sunshine condition in Sichuan Basin, China. In four year ´ location environments, we tested the grain yield and its components of three SHY varieties and seven common high-yield varieties (control), as well as the characteristics of dry matter accumulation and translocation. The average yield of SHY varieties over environments reached 9338 kg ha^-1, which was 24.2% higher than that of the control. SHY varieties had average spike number of 449×10⁴ ha^-1, grain number per spike of 42.3, grain number of 18 825 m^-2, and thousand-grain weight of 47.8 g, which were 8.2%, 10.7%, 18.3%, and 0.6% higher than those of the control. At various growth stages, SHY varieties had significantly higher rates and larger amounts of dry matter accumulation, especially in the early growing period. For example, the amount of dry matter accumulation in the SHY varieties was 11.1% and 18.2% higher than that of the control at tillering and jointing stages, respectively. Moreover, compared with the control, SHY varieties had significantly higher amount of dry matter translocation, translocation efficiency, and contribution of remobilization to grain. At maturity, the proportion of dry matter in vegetative organs was 1.2%–3.5% lower in SHY variety than in the control. There were significant correlations between grain yield and colony dry matter at various growth stages and individual dry matter at tillering and jointing stages. SHY varieties tested in this study possess strong tillering ability, early vigorous growth, and high levels of dry matter accumulation and translocation into grains, which ultimately result in the high grain yield.

Effects of Leaf Removal on Canopy Apparent Photosynthesis and Individual Leaf Photosynthetic Characteristics in Summer Maize under High Plant Density

LIU Tie-Ning,XU Cai-Long,GU Li-Min,DONG Shu-Ting

Acta Agron Sin. 2014, 40(01):  143-153.  doi:10.3724/SP.J.1006.2014.00143

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The improved grain yield of modern maize hybrids is due to the increased plant population density. However, the high plant density makes the solar radiation intercepted by ear leaves decreased, and the growth rate of individual plant suppressed. Consequently, how to coordinate the relationship between canopy apparent photosynthesis (CAP) and individual leaf photosynthesis capacity under high plant density is an important problem we are facing. A field experiment was conducted using summer maize (Zea mays L.) Zhengdan 958 (a compact cultivar) and Jinhai 5 (a semi-compact cultivar) grown at a plant density of 105 000 plants ha^–1, to research the impact of leaf removal on CAP, individual leaf photosynthetic characteristics and anti-oxidative metabolism, which will provide theoretical basis and technical supports for super-high-yield cultivation and breeding. At three days after anthesis (DAA), the defoliation treatments consisted of two (S₁), four (S₂) or six leaves (S₃) removal from the top of a plant were imposed, and no leaf removal as control (S₀). The results indicated that leaf removal could significantly improve light transmission ratio (LT) after anthesis, but decrease leaf area index (LAI) of S₂ and S₃, resulting in the decrease of effective quantum yield of PSII (Φ_PSII) and maximal efficiency of photosystem II photochemistry (F_v/F_m) sharply because of light leakage losses. CAP was significantly affected by defoliation treatments: for S₁, CAP increased and longer durations of CAP and LAI were maintained during grain filling, resulting in a higher grain yield, whereas CAP in S₂ and S₃ treatments was inhibited and drastically declined, indicating that CAP is closely related to changes in available leaf area. Compared with S₀, the CAP in S₁ treatment increased by 12.49% for Zhengdan 958, and by 23.08% for Jinhai 5, indicating that effect of excising two leaves on CAP was more apparent for Jinhai5 than for Zhengdan 958. Moreover, an increase in net photosynthetic rate (P_n), stomatal conductance (g_s) and the chlorophyll content (Chl) of ear leaf in S₂ and S₃ treatments was observed prior to 26 DAA, and S₁ treatment had the advantage of individual photosynthetic capacity, thereafter. A analysis of leaf senescence revealed that activities of superoxide dismutase (SOD) and peroxidase (POD) in S₂ and S₃ treatments were significantly suppressed since 13 DAA compared with control, whereas those in S₁ were markedly enhanced, indicating that leaf senescence was delayed by excising two leaves under high plant densities. However, the content of MDA in S₁ was decreased. Among all the defoliation treatments, maize plants under two-leaf removal condition had higher P_n, LAI and anti-oxidative enzyme activity as well as lower MDA content during grain filling, leading to a higher CAP. The results indicated that excising two leaves made plants of both maize cultivars more tolerant to high plant density of 105 000 plants ha^-1 due to the lesser damage and a better photosynthetic capacity in an ear leaf as well as a more efficient canopy structure, resulting in a better coordination between population and individuals. In addition, relative to Zhengdan 958, the effects of leaf removal on Jinhai 5 were more apparent.

Effects of Light, Nitrogen and Their Interaction on Grain Yield and Matter Production Characteristics of Japonica Super Rice

WANG Ya-Jiang,GE Meng-Jie,YAN Xi-Ting,WEI Hai-Yan,ZHANG Hong-Cheng,DAI Qi-Gen,HUO Zhong-Yang,XU Ke

Acta Agron Sin. 2014, 40(01):  154-165.  doi:10.3724/SP.J.1006.2014.00154

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Field experiment was conducted using japonica super rice Nanjing 44 and Ningjing 3 with two nitrogen fertilization levels (N10: 150 kg ha^-1, N20: 300 kg ha^-1) and three shading treatments (L1: no shading, L2: shading 20 days before heading, L3: shading 20 days after heading) to study theeffects of light, nitrogen and their interaction on grain yield and matter production. Results showed that, compared with L1 treatment, L2 not only reduced the effective panicles and grains per panicle, resulting in the decline of total spikelets by 24.81% to 35.63%, but also significantly reduced the tiller number and leaf area index at heading by 2.90%–6.44% and 19.02%–27.17% respectively, causing photosynthetic potential, dry matter accumulation decreased significantly from heading to maturity, and at last the final yield decreased by 27.23%–35.26%. Compared with L1 treatment, L3 mainly affected photosynthate accumulation from heading to maturity, leading to seed setting rate and grain weight significantly decreased by 1.49%–4.48% and 5.54%–9.17% respectively, and the final yield decreased by 10.91%–18.47%. UnderL2 condition, with increasing nitrogen level, tiller number and leaf area index at heading increased significantly, resulting in photosynthetic potential, dry matter accumulation increased significantly from heading to maturity, and the ultimately effective panicles, number of grains per panicle, total number of spikelets and the yield improved significantly. Under L3 condition, with increasing nitrogen level, photosynthate accumulation from heading to maturity increased significantly, dry matter translocation from stems and leavesto the panicle increased significantly, meanwhile, translocation rate and contribution rate were further improved, and the ultimate yield improved significantly. This indicated that nitrogen fertilizer could partially offset the impact of low light stress on the matter production and yield of japonica super rice.

RESEARCH NOTES

Ultrastructure of Central Cell before and after Fertilization in Sugar Beet (Beta vulgaris)

LI Wei,SHEN Jia-Heng,GUO De-Dong

Acta Agron Sin. 2014, 40(01):  166-173.  doi:10.3724/SP.J.1006.2014. 00166

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The ultrastructural changes of central cell before and after fertilization were studied with TEM to provide more information for reproductive biology of sugar beet and relative research. The results indicated that the changes of central cell before and after fertilization mainly occurred in nucleus and cytoplasm around. Fusion of polar nuclei took place early at bud stage. The nucleolus of secondary nucleus was bipolar with notable fibrous and particle core. Sometimes, there was extra small nucleolus and nucleolus vacuole. Cytoplasm surrounding secondary nucleus was rich in organelles, including mitochondria, plastids with or without starch grain, Golgi body, ribosomes and rough endoplasmic reticulum (rER). After fertilization, a striking feature of cytoplasm surrounding nucleus was the well developed amoeboid plastids, which were numerous and various, filling with starch gains. Soon after that, primary endosperm nucleus divided into two free nuclei. During division, nucleolus disappeared and nuclear membrane disintegrated into small vesicles. Also, there was an obvious decrease in rER and an increase in smooth endoplasmic reticulum (sER). Overall, central cell was active before and after fertilization.

Genetic Diversity Analysis of Wild Adzuki Bean Germplasm and Its Relatives by Using SSR Markers

LIU Chang-You,FAN Bao-Jie,CAO Zhi-Min,SU Qiu-Zhu,WANG Yan,ZHANG Zhi-Xiao,CHENG Xu-Zhen,TIAN Jing

Acta Agron Sin. 2014, 40(01):  174-180.  doi:10.3724/SP.J.1006.2014. 00174

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Wild Adzuki bean (V. angularis var. nipponensis) germplasm and its relatives are very important materials for adzuki bean breeding. In this paper, genetic diversity of 96 accessions of wild types, relatives and cultivated adzuki beans were analyzed by using 28 pairs of polymorphic SSR makers. The results showed that a total of 255 alleles were detected in all the accessions. The average number of allele per SSR locus was 9.10. The range of genetic diversity index (polymorphic information content, PIC value) was from 0.374 to 0.865, with an average of 0.722. The results revealed that there were abundant genetic variations between wild adzuki bean and its relatives Vigna minima. Both cluster and principal coordinate analysis (PCO analysis) suggested that there was a high genetic differentiation between wild adzuki beans and its relatives, and they could be distinguished from each other clearly according to their origins, suggesting that the locations of wild adzuki bean accessions affect their genetic variations. When analyzed the relationship between adzuki bean varieties and wild adzuki bean accessions, we found that their genetic distance was more closer to Japanese wild adzuki bean accessions than to domestic accessions, indicating that more Japanese adzuki bean accessions were used in Chinese adzuki bean breeding, and showing that our works for domestic wild adzuki bean resources collection and use is behind Japan. The present study provides some information in collection and conservation of domestic wild adzuki bean accessions, and the result is useful for evaluating and using these resources to find useful genes.

Effect of Different Planting Patterns on Maize Growth and Yield in Western Liaoning Province

BAI Wei,SUN Zhan-Xiang,ZHENG Jia-Ming,HOU Zhi-Yan,LIU Yang,FENG Liang-Shan,YANG Ning

Acta Agron Sin. 2014, 40(01):  181-189.  doi:10.3724/SP.J.1006.2014.00181

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The study of planting patterns is critical to improving maize yield. Based on a field experiment,we investigated the effect of three planting patterns (three ratio space, big ridge double line and equal line) on maize growth, photosynthetic characteristics and yield using two varieties suitable for high-density (Zhengdan 958) and middle-density (Shenyu 21). Our results indicated that the yield and growth of maize were dramatically influenced by various planting patterns. High-density variety was suitable for using the pattern of big ridge double line which promoted plant height, stem diameter, leaf area and photosynthetic efficiency of maize. The yield averaged 8882.36 kg ha^-1 for two years, with an increasing rate of 6.51% compared with the control. This increase in biomass was largely contributed by hundred-grain weight and number of lines per ear. But differently, middle-density variety, planted with both patterns of big ridge double line and three ratio spaces, showed a higher yield. These two planting patterns could also increase plant height, stem diameter, leaf area and photosynthetic efficiency in maize. The 2-year-averaged yields were 8294.58 kg ha^-1 and 8188.30 kg ha^-1, for the two patterns of big ridge double line and equal line, respectively. An increasing rate of 21.36% for big ridge double line and 19.81% for equal line spacing were observed compared with the control, which mainly contributed by the high number of kernels per line. Our results indicated that big ridge double line is an optimal planting pattern to improve maize yield in the western Liaoning Province.