Table of Content

12 November 2015, Volume 41 Issue 11

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Identification and Map-based Cloning of rad-1 and rad-2, Two Rice Architecture Determinant Mutants

NIU Jing,CHEN Sai-Hua*,ZHAO Jie-Yu,ZENG Zhao-Qiong,CAI Mao-Hong,ZHOU Liang,LIU Xi,JIANG Ling,WAN Jian-Min

Acta Agron Sin. 2015, 41(11):  1621-1631.  doi:10.3724/SP.J.1006.2015.01621

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Plant architecture is a key element of crop yield and also taken as a criterion in breeding. In this study, two rice architecture determinant mutants, rad-1 and rad-2 were selected from Gamma-radiation induced mutants of rice cultivar Asominori. Each of them shows winding seedlings, dwarf plants and thereby decreased yield. It has been estimated that rad-1 and rad-2 are allelic to each other by allelism test and linkage analysis. After map-based cloning, the responsible gene for the mutations was restricted within a 230 kb region in chromosome 7. Sequence analysis revealed that OsFH5 gene, encoding a forming-like protein altered both in rad-1 and rad-2. An 8-bp deletion in exon 2 in rad-1 and a single nucleotide change in intron 14 in rad-2 made frame-shift reading and produced truncated proteins. OsFH5 gene exhibited constitutive expression in tested tissues. Compared with the wild type, prominent decline of OsFH5 gene was observed in each mutant. In seedlings, loss-function of OsFH5 gene resulted in irregular cell growth in leaf sheath and shorter cells in inner husk, which therefore caused short grain and lower grain weight. By quantitative RT-PCR analysis, several auxin response factors were dramatically down-regulated in rad-2, which suggested that OsFH5 may affect the response to auxin in rice.

Genome-wide Identification, Expression, and Regulation Analysis of BEL1-like Family Genes in Maize

CAO Zheng,LI Man-Fei,SUN Wei,ZHANG Dan,ZHANG Zu-Xin

Acta Agron Sin. 2015, 41(11):  1632-1639.  doi:10.3724/SP.J.1006.2015.01632

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The BEL1-like family (BELL) proteins, that are ubiquitous homeodomain transcription factors among plant species, interact with KNOTTED1-like protein to regulate a range of developmental processes by binding specific cis-acting element to modulate gene expression. BELL family genes in maize still need to be studied systematically. Here, we identified 15 BELL family genes (ZmBELLs) in maize genome using the Hidden Markov Model (HMM). These ZmBELLs distributed non-uniformly in seven chromosomes of maize, were clustered into two groups on the basis of the similarity with their orthologs in Arabidopsis thaliana. Furthermore, these ZmBELLs exhibited different expression[1]patterns in eight tissues studied, showing strong tissues-specific expression. Moreover, based on co-expression profiles and specific motif bound by BEL1-like protein, we predicted 86 genes showing co-expression pattern with 12 ZmBELLs in eight tissues studied and harboring specific motif bound by BEL1-like protein in the promoter region. The results could provide valuable informations for dissecting function and molecular mechanism of ZmBELLs in maize.

Composition and Selection of TaGW2-6A Alleles for Wheat Kernel Weight

KOU Cheng,GAO Xin,LI Li-Qun,LI Yang,WANG Zhong-Hua,LI Xue-Jun*

Acta Agron Sin. 2015, 41(11):  1640-1647.  doi:10.3724/SP.J.1006.2015.01640

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TaGW2 on chromosome 6A is a key gene governing kernel size of wheat (Triticum aestivum L.). There are a single T-base insertion in the eighth exon of TaGW2 (977 bp) and two SNPs (Hap-6A-A and Hap-6A-G) in the promoter region. In this study, 316 wheat varieties (lines) were detected by high resolution melting curve (HRM) analysis and Hap-6A-P1/P2 molecular marker for TaGW2-6A allelic variations and their correlations with kernel length, kernel width, and thousand-kernel weight were analyzed. Furthermore, the TaGW2-6A allelic variations were traced in the pedigree of the famous large-kernel variety Zhoumai 22. In the 977 bp position, 61 and 255 lines were detected with and without the T-base insertion, which were designated 977T and 977- genotypes, respectively. In the 977T genotypes, 29 lines were Hap-6A-A (TA) haplotype and 32 lines were Hap-6A-G (TG) haplotype. In the 977- genotypes, 160 lines were Hap-6A-A (-A) haplotype and 95 lines were Hap-6A-G (-G) haplotype. Significant difference was found in kernel length (P < 0.05), kernel width (P < 0.001) and thousand-kernel weight (P < 0.001) between 977T and 977- genotypes. Similarly, significant difference was also found in kernel length (P < 0.05), kernel width (P < 0.05) and thousand-kernel weight (P < 0.001) between Hap-6A-A and Hap-6A-G haplotypes. The allelic variation in TaGW2-6A encoding region and the promoter region jointly contributed to kernel size, and the TA haplotype was superior to -A, TG, and -G haplotypes in increasing kernel width and weight. According to pedigree analysis, the Zhoumai 22 inherited the TA haplotype from the parent Huixianhong, not form the popular parent Zhou 8425B. This haplotype is inheritable stably but tends to be lost in the process of wheat breeding. The results of this study provide not only a high-throughput molecular technique to detect wheat TA haplotype but also breeding materials in marker-assisted selection of wheat.

Effect of 1BL/1RS Translocation on Gluten Protein Fraction Quantities and Dough Rheological Properties

ZHAO De-Hui,YAN Jun,HUANG Yu-Lian,XIA Xian-Chun,ZHANG Yan,TIAN Yu-Bing,HE Zhong-Hu,ZHANG Yong

Acta Agron Sin. 2015, 41(11):  1648-1656.  doi:10.3724/SP.J.1006.2015.01648

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Understanding the effect of gluten protein fractions on major dough rheological quality traits among 1BL/1RS and non-1BL/1RS lines will facilitate quality improvement in wheat. Fourteen advanced facultative wheat lines derived from leading cultivars Shiluan 02-1 without 1BL/1RS and Zhoumai 16 with 1BL/1RS were grown in Anyang and Jiaozuo in Henan province in the 2012–2013 growing season. The gluten protein fractions were quantified with reversed-phase ultra-performance liquid chromatography (RP-UPLC) and size-exclusion ultra-performance liquid chromatography (SE-UPLC), and their correlations with dough rheological properties were determined. The results showed that Extensograph extensibility and maximum resistance, content of unextractable glutenin polymeric protein, quantity of gluten protein fractions and their ratios received significant influence from the presence of 1BL/1RS translocation and the line within group, whereas Extensograph extension area, content of glutenin and the ratio of gliadin-to-glutenin were predominantly affected by the line within group. Significant correlations were observed between gluten protein fraction quantities and dough rheological parameters in the 1BL/1RS and non-1BL/1RS lines. The 1BL/1RS lines with good dough rheological quality exhibited high content of unextractable glutenin polymeric proteins, which was significantly and positively correlated with Extensograph extension area (r = 0.92, P < 0.001), extensibility (r = 0.92, P < 0.001) and maximum resistance (r = 0.80, P < 0.01). The non-1BL/1RS lines with good dough rheological quality showed low ratio of gliadin-to-glutenin, which was significantly and negatively correlated with Extensograph extension area (r = -0.91, P < 0.001) and maximum resistance (r = -0.88, P < 0.001). These results may guide genotypic selection in early generations to improve the dough rheological properties when 1BL/1RS is used in breeding program.

Sequence and Pathogenicity of Recombined Soybean Mosaic Virus Isolate from Hebei Province, China

LIN Jing,YANG Yong-Qing,HOU Wen-Huan,YANG Chun-Yan,XIE Ling-Qin,ZHI Hai-Jian,ZHANG Meng-Chen

Acta Agron Sin. 2015, 41(11):  1657-1662.  doi:10.3724/SP.J.1006.2015.01657

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Recombined Soybean mosaic virus (SMV-R), which is prevalent in many soybean production regions, is a novel type of SMV. To clarify the characteristics of recombinant SMV structure and pathogenicity of SMV-R, we sequenced the whole genomes of a SMV-R isolate (HB-RS) from Hebei province of China, and compered the difference of SMV infection and accumulation in four soybean cultivars with SMV-R. The results showed that besides the poly-A tail, HB-RS consists of 9993 nucleotides, encoding only one open reading frame and 3202 amino acids. Phylogenetic analysis showed that the HB-RS isolate was clustered with other two recombined SMV isolates. Resistance identification results showed that the average disease index of four cultivars resistant to HB-RS and Sc6 was 59.5 and 60.5, respectively. The same soybean cultivar had different symptoms and resistance levels to different strains (isolates), Jidou 17 showed high resistance to Sc6 and moderate resistance to HB-RS. These results indicated that soybean resistance to SMV exists strain (isolate) specialization. Additionally, the pathogenicity test showed that accumulation of HB-RS in four cultivars was higher than that of Sc6, indicating that HB-RS is more adaptable to the host plants. The host with highest accumulation of HB-RS was Nannong 1138-2, with 522-fold of reference virus accumulation, and the following was Wuxing 1 (471 U), Jihuang 13 (199 U) and, Jidou 17 (only 90 U), suggesting that HB-RS has a more survival adaptability in the soybean host. However different resistance levels to HB-RS were observed in various soybean cultivars and Jidou 17 could be used as a resistant cultivar in production or parents in further breeding.

Cloning and Expression of BnFAD2-C1 Gene Involved in Brassica napus and Analysis of Transcription Regulation Elements

LIU Fang,LIU Rui-Yang,PENG Ye,GUAN Chun-Yun

Acta Agron Sin. 2015, 41(11):  1663-1670.  doi:10.3724/SP.J.1006.2015.01663

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Fatty acid desaturase gene (FAD2) is a key factor in regulating oleic acid content. There are four copies located on chromosomes A1, C1, A5, and C5 in Brassica napus. One copy containing 1155 bp open reading frame was cloned with previous research method and named as BnFAD2-C1 which was location on chromosome C1 based on the genome database information of oleracea and oilseed. Then the untranslated regions (UTR) of 5′and 3′end with 175 bp and 212 bp length respectively were cloned by RACE (rapid-amplification of cDNA ends) technique. The expression pattern of BnFAD2-C1 gene was identified using quantity PCR technique, showing a seed-specific inducible expression in mid developmental seeds and a background-level expression in root, flower and siliqua wall. The promoter and intron region were also cloned and analyzed using PLACE and PlantCARE websites to predict some potential cis-elements in regulating BnFAD2-C1 gene transcription. At the same time, jasmonic acid (JA) was inferred to make certain contributions to regulate BnFAD2-C1 gene expression showing a changeable expression quantity when treated with Jasmonic acid.

Genetic Diversity of Wheat Germplasm Resistant to Sharp Eyespot and Genotyping of Resistance Loci Using SSR Markers

LIU Ying,ZHANG Qiao-Feng,FU Bi-Sheng,CAI Shi-Bin,JIANG Yan-Jie,ZHANG Zhi-Liang,DENG Yuan-Yu,WU Ji-Zhong,DAI Ting-Bo

Acta Agron Sin. 2015, 41(11):  1671-1681.  doi:10.3724/SP.J.1006.2015.01671

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A three-year filed identification with artificial inoculation was carried out to validate 88 wheat germplasm resources resistant to sharp eyespot identified in previous studies. Thirty-two accessions showed resistance or moderate resistance to sharp eyespot. Rich genetic diversity among these resistant resources was revealed by 59 SSR markers across the whole wheat genome. A total of 308 alleles were detected with 2–13 alleles per marker and an average of 5.2. The polymorphism information content (PIC) ranged from 0.12 to 0.89 with an average of 0.61. The clustering and principal component analysis (PCA) based on molecular marker data indicated that the 32 resistant accessions were grouped in improved variety (including alien varieties) and landraces, which was consistent with geographic distribution. The 32 resistant varieties were genotyped with 14 SSR markers closely linked to QTLs for sharp eyespot resistance. Xwmc154 on 2BS and Xbarc126 on 7DS were frequently detected in the resistant resources. As a consequence, they are recommended in marker-assisted selection. Only one known resistance QTL was detected in varieties Wunong 148, Shaan 983, Shaannong 78, Coker 983, H-Line, Mason and Compair, whereas none resistance QTL was found in Tyalt. These varieties might carry novel resistance genes/QTLs against wheat sharp eyespot and are promising in wheat breeding.

Overexpression of Vacuole H⁺-ATPase E Subunit Gene SiVHA-E from Foxtail Millet Enhances Salt Resistance in Transgenic Arabidopsis thaliana

FENG Lu,ZHONG Li,CHEN Dan-Dan,MA You-Zhi,XU Zhao-Shi,LI Lian-Cheng,ZHOU Yong-Bin,CHEN Ming,ZHANG Xiao-Hong

Acta Agron Sin. 2015, 41(11):  1682-1691.  doi:10.3724/SP.J.1006.2015.01682

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The V-H+-ATPase plays an important role in processes of plant growth, development and response to stresses. In this research, SiVHA-E, a V-H+-ATPase E subunit gene, was cloned from millet by the Blast analysis against GenBank database. Phylogenetic tree showed that the gene belongs to E1/E3 subgroup and is close with ZmVHA-EL, a V-H+-ATPase E subunit from maize. The quantitative Real-time PCR (qRT-PCR) analysis revealed that the expression levels of SiVHA-E were up-regulated under treatments of high-salt, exogenous MeJA, SA, and ABA hormones, while down-regulated under stresses of cold and low nitrogen. Protein subcellular localization analysis using protoplast showed that SiVHA-E is located on tonoplast. The results of salt tolerance assay showed that the germination rate of SiVHA-E transgenic lines was significantly higher than that of wild type plant under salt stress. During seedlings period, the root lengths were significantly longer as well as fresh weight and survival rate were significantly higher in transgenic lines than in wild type plant under salt treatment. Compared with wild type plant, transgenic plant reduced the content of Na+ and increased the relative water content inside cells. In addition, the results of germination experiment used ABA showed that SiVHA-E transgenic Arabidopsis was more sensitive to ABA than wild type plant during post-germination. In short, overexpressing SiVHA-E in transgenic Arabidopsis lines enhances salt tolerance, which might be relates to positive regulation of ABA signaling pathway or reduction of Na+ accumulation and water loss in transgenic plants.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Key Components of Eating Quality and their Dynamic Accumulation in Vegetable Soybean Varieties [Glycine max (L.) Merr.]

ZHANG Qiu-Ying,LI Yan-Sheng,LIU Chang-Kai,TIAN Bo-Wen,TU Bing-Jie,MAO Jian-Wei

Acta Agron Sin. 2015, 41(11):  1692-1700.  doi:10.3724/SP.J.1006.2015.01692

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The eating quality and seed chemical compositions of 30 vegetable soybean cultivars (line), as well as their correlations were analyzed. At the same time, main quality compositions and their roles for eating quality were investigated by path analysis, while the dynamic accumulation of each component was also studied with three cultivars differing in soluble sugar content. Results showed that the cumulative contribution of sucrose, fructose + glucose, raffinose, stachyose, protein, free amino acid and oil for eating quality was 67.8%. A significant positive correlation was found between eating quality score and sucrose content (0.864**), while a significant negative correlation between eating quality score and protein content (–0.439*). The average content of raffinose and stachyose at fresh harvest stage was only 7.4% and 12.4% of that at mature stage respectively, which had much less negative impact on eating quality of vegetable soybean than field grain soybean. The optimum harvest time for fresh pods was at 42 days after flowering and could last for one week with highest sucrose content and lowest raffinose and stachyose contents. Besides, the average content of amino acids was higher and fructose + glucose contents were medium, and protein content was 3% less than that at mature stage. Postponing the harvest time deteriorated eating quality due to decreased content in sucrose and monosaccharide, increased content in fat and protein contents, as well as a dramatic increase in raffinose and stachyose contents.

Effect of Ethephon and Nitrogen Fertilizer on Nitrogen Uptake, Nitrogen Use Efficiency and Yield of Summer Maize

YE De-Lian,WANG Yu-Bin,ZHOU Lin，LI Jian-Min,DUAN Liu-Sheng,ZHANG Ming-Cai,LI Zhao-Hu

Acta Agron Sin. 2015, 41(11):  1701-1710. 

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A field experiment using maize hybrid Zhengdan 958 was conducted to study effect of ethephon (0 and 180 g ha^–1) and nitrogen fertilizer (0, 75, 150, and 225 kg N ha^–1) on summer maize yield and yield components, nitrogen uptake, nitrogen use and SPAD value. The results showed that ethephon significantly decreased nitrogen uptake and N uptake efficiency, whereas markedly increased N utilization efficiency. N agronomic efficiency under ethephon treatment was 32.7%–34.6% more than that under control, and ethephon had no negative effect on maize yield and yield components. With increase nitrogen fertilizer of application, maize yield, yield components and nitrogen uptake were increased, but N uptake efficiency, N utilization efficiency, N partial factor productivity and N agronomic efficiency were decreased. Nitrogen uptake under 225 kg N ha^–1 treatment was 68.4%–91.8% more than that under 0 kg N ha^–1. However there was no difference for nitrogen uptake between 225 kg N ha^–1 and 150 kg N ha^–1 treatments. Significant effect of ethephon × nitrogen was observed on nitrogen uptake, N uptake efficiency and N agronomic efficiency. Ethephon as well as higher nitrogen rate increased SPAD value of ear leaf during grain filling stage, while there was no significant interaction between ethephon and nitrogen fertilizer on SPAD value. Correlation analysis indicated that summer maize yield was significantly positively correlated with nitrogen uptake at silking stage and harvest stage and with SPAD value of ear leaf.

Advantages and Their Formation Characteristics of the Highest Population Productivity of Nitrogen Fertilization in Japonica/Indica Hybrid Rice of Yongyou Series

MENG Tian-Yao,XU Jun-Wei,SHAO Zi-Bin,GE Meng-Jie2,ZHANG Hong-Cheng,WEI Hai-Yan,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,GUO Bao-Wei,JING Pei-Pei

Acta Agron Sin. 2015, 41(11):  1711-1725.  doi:10.3724/SP.J.1006.2015.01711

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A field experiment was conducted using the representative varieties of four types (indica/japonica hybrid rice, inbred japonica rice, hybrid japonica rice, and hybrid indica rice) to achieve the highest rice yield for each variety that is defined as the highest population productivity of N fertilization at six nitrogen fertilization levels (0, 187.5, 225.0, 262.5, 300.0, and 337.5 kg ha^-1). On this basis, the differences in yield components, duration of main growth stages, dry matter weight, and leaf area index at main growth stages for four types were studied. The results were as follows: (1) The highest grain yield  rice was achieved under 225.0–262.5 kg ha^-1 nitrogen application for hybrid indica, 300 kg ha^-1for inbred japonica rice, 262.5–300.0 kg ha^-1for hybrid japonica rice and 262.5–300.0 kg ha^-1 for indica/japonica hybrid rice. (2) The population productivity of indica/japonica hybrid rice was the highest, followed by hybrid japonica rice, inbred japonica rice, and hybrid indica rice. Indica/japonica hybrid rice had more spikelets and spikelets per panicle, but great fluctuation was observed in number of spikelets per panicle across two years. Inbred japonica rice had more panicles and higher seed-setting rate while hybrid japonica rice had the highest 1000-grain yield weight. (3) The longest duration from sowing to heading stages was observed for hybrid japonica rice. The duration from heading to maturity of indica/japonica hybrid rice was about 60 d, which was significantly higher than that of other three variety types. Grain yield per day of japonica/indica hybrids was the highest among the four variety types in two years. (4) The dry matter weight and leaf area index at heading, 20 d after heading, and maturity stage of indica/japonica hybrid rice were higher higher than thoes of other three variety types. As for dry matter accumulation, indica/japonica hybrid rice was the highest from heading to maturity stage. Moreover, the leaf area duration from jointing to heading and from heading to maturity in indica/japonica hybrid rice was also higher than that of other three variety types. Great yield of japonica/indica hybrids of Yongyou series over other three variety types is mainly attributed to more spikelets per panicle, longer filling phase, higher grain yield per day and biomass production after heading.

Simulating Wheat Yield and Soil Moisture under Alternative No-tillage and Subsoil Tillage in Response to Fertilization Levels in Weibei Highlands

ZHANG Yu-Jiao,LI Jun,GUO Zheng,YUE Zhi-Fang

Acta Agron Sin. 2015, 41(11):  1726-1739.  doi:10.3724/SP.J.1006.2015.01726

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This study aimed at understanding the responses of grain yield and soil moisture to fertilization level in dryland winter wheat under long-term alternative no-tillage and subsoil tillage. The WinEPIC model was employed on the basis of precision verification with five fertilization levels (T1, N 75 kg ha^-1+P₂O₅ 60 kg ha^-1; T2, N 120 kg ha^-1+P₂O₅ 90 kg ha^-1; T3, N 150 kg ha^-1+P₂O₅ 120 kg ha^-1; T4, N 180 kg ha^-1+P₂O₅ 150 kg ha^-1; and T5, N 255 kg ha^-1+P₂O₅ 90 kg ha^-1) and the simulation period was from 1980 to 2009. During the 30-year period, water consumption in the growing season and water use efficiency of winter wheat tended to decrease in a fluctuating manner at different fertilization levels with the ranking sequence of T5>T4>T3>T2>T1. In the 0–5 m soil depth, the monthly available soil moisture tended to decrease in a seasonally fluctuating manner and reduced with the increase of fertilization amount. The soil desiccation rates from T1 to T5 were 13.5, 17.1, 17.4, 20.1, and 23.9 mm per year, respectively. During the simulation period, the soil humidity in 0–1.5 m soil layer fluctuated with the seasonal rainfall. A stable dry soil layer was found under all fertilization levels which was 1.5–2.0 m under T1, 1.5–3.0 m under T2 and T3, and 1.5–4.0 m under T4 and T5. These results indicate that grain yield and water consumption of winter wheat may increase with more fertilizer input, however, the dried soil layer is thickened. In a comprehensive consideration, we suggest N 150 kg ha^-1+P₂O₅ 120 kg ha^-1 to be the optimal fertilization rates in winter wheat under long-term alternative no-tillage and subsoil tillage in Weibei Highlands.

Effects of Shade and Light Recovery on Soybean Cultivars (Lines) and Its Relationship with Yield in Relay Strip Intercropping System

WU Yu-Shan,GONG Wan-Zhuo,LIAO Dun-Ping,WU Xiao-Ling,YANG Feng,LIU Wei-Guo,YONG Tai-Wen,YANG Wen-Yu

Acta Agron Sin. 2015, 41(11):  1740-1747.  doi:10.3724/SP.J.1006.2015.01740

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A field experiment was conducted to compare agronomic traits during shade and light recovery periods between high yield and low yield soybean cultivars undershade net or in “maize-soybean” relay strip intercropping in 2013 and 2014. Twenty typical soybean varieties with dirrerent yield levels in relay cropping in south of China were used. The results showed that during shade period stem dry weight and leaf dry weight were significantly lower than those of control , the dry weght natio of stem and leaf was 58.4% and 41.6% respectively under shade. Compared with the high yield soybeans, low yield cultivars had significantly higher decline rate of aboveground dry weight, stem length , stem length/ stem diameter, stem length/ aboveground dry weight, stem length/ leaf area. and the yield was positively correlated with aboveground dry weight, and negatively correlated with stem weight ratio during shade period. During light recovery period, aboveground dry weight and leaf area increased rapidly, soybean showed more leaf weight ratio, stem dry weight and leaf dry weight were 47.7% and 52.3% respectively at 30 days after the recovery of light. High yield soybeans had significantly higher aboveground dry weight, leaf area, stem diameter, leaf weightratio and significantly smaller stem length/ stem diameter, stem length/aboveground dry weight, stem length/leaf area. In light recovery duration, yield was positively correlated with aboveground dry weight, stem diameter, leaf area,and leaf weight ratio, and negatively correlated with stem length/ stem diameter, stem length/ aboveground dry weight. Stem length/ aboveground dry weight, stem diameter and leaf weight ratio were the three biggest variables determing yield selected by regression analysis. These results concluded that soybean cultivars with smaller stem length, larger aboveground dry weight and leaf area during shade period and smaller stem length/ aboveground dry weight, larger stem diameter and higher leaf weight ratio could obtain high yield in relay strip intercropping.

Effects of Different Species in Echinochloa on Photosynthetic Characteristics and Grain Yield in Rice under Alternate Wetting and Moderate Drying Condition

ZHANG Zi-Chang,LI Yong-Feng,YANG Xia,LU Fan,QIU Guang,LI Jian-Wei

Acta Agron Sin. 2015, 41(11):  1748-1757.  doi:10.3724/SP.J.1006.2015.01748

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In order to investigate the effects of different barnyardgrass species on photosynthetic characteristic and grain yield of rice, two rice cultivars, Liangyoupeijiu (an indica hybrid cultivar) and Nanjing 9108 (a japonica cultivar), were co-cultured with four barnyardgrass species from transplanting to maturity under alternate wetting and moderate drying condition. The treatments were designed as follow: weed free (control), rice with Echinochloa crusgalli var. mitis (T1), rice with Echinochloa crusgalli (T2), rice with Echinochloa crusgali var. zelayensis (T3), and rice with Echinochloa colonum (T4). The results showed that the degree of interference of barnyardgrass on rice yield depended on different barnyardgrass species and rice cultivars. The interference intensity of barnyardgrass was in the order of T3>T1>T2>T4, and grain yield loss rate in Liangyoupeijiu was less than that in Nanjing 9108. T1, T2, T3 and T4 treatments respectively reduced 11.16%–13.78%, 10.19%–10.60%, 19.00%–23.79% and 0.50%–1.57%, for Liangyoupeijiu of the grain yield and 38.44%–45.51%, 31.29%–36.86%, 54.88%–60.65%, and 8.28%–15.14% for Nanjing9108, T1, T2 and T3 significantly reduced rice grain yield, while the effect of T4 was significant for Nanijng 9108 but not for Liangyoupeijiu when compared with CK. Moreover T1, T2, and T3 had no effects on leaf area index and contents of photosynthetic pigments for Liangyoupeijiu, but Nanjing 9108 significantly reduced leaf area index and increased contents of photosynthetic pigments under the same treatment condition. Furthermore, four treatments significantly reduced rice canopy light transmission, leaf photosynthetic rate, stomata conductance, transpiration rate and dry matter accumulation during grain filling stage. The results indicated that the decrease in canopy light transmission，photosynthetic rate, transpiration rate, stomata conductance and the increase in some degree in contents of photosynthetic pigments during grain filling stage may contribute to grain yield reduction of rice.

RESEARCH ACTIVITIES

Expression Analysis and eQTL Mapping of BnTT3 Gene in Brassica napus L.

LU Kun,QU Cun-Min,LI Sha,ZHAO Hui-Yan,WANG Rui,XU Xin-Fu,LIANG Ying,LI Jia-Na

Acta Agron Sin. 2015, 41(11):  1758-1766.  doi:10.3724/SP.J.1006.2015.01758

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In flavonoid biosynthesis pathway, the key enzyme dihydroflavonol 4-reductase (DFR) involved in the proanthocyanidin and anthocyanin biosynthesis pathway is encoded by TRANSPARENT TESTA 3 (TT3) gene. The objective of this research was to identify the upstream regulatory networks of BnTT3 using the composite interval mapping method (CIM). Hence, we performed an eQTL analysis for the transcript-level variation of BnTT3 gene in seeds at 40 days after flower (DAF) in 94 recombinant inbred lines (RILs) derived from a cross between the yellow-seeded female parent GH06 and black-seeded male parent ZY821. Five eQTLs for expression levels of BnTT3 were detected on four different chromosomes (A03, A08, A09, and C01) in B. napus, accounting for 5.22% to 24.05% of phenotypic variation. Two major eQTLs were found and located among the markers KS10260–KBrB019I24.15 and B055B21-5–KS30880 of chromosome A09, with explained 24.05% and 16.55% of phenotypic variation, respectively. Three minor eQTLs were also detected to be located on chromosomes A03, A08 and C01. The flanking sequences with 200 kb of two major eQTLs on chromosome A09 of B. napus showed well synteny to those of A. thaliana, Brassica rapa, Brassica oleracea and other Brassiceae relatives. Furthermore, the annotation results showed that they belong to the trans-QTL, containing 78 genes in the two trans-QTL regions. Some transcription factors (MYB51, MYB52, and bZIP5) might be upstream regulatory factors associated with transcriptional regulation of BnTT3. Therefore, further study about these genes function will be helpful to elucidate the molecular mechanism of the seed coat colour formation, as well as lay the foundation for selecting candidate genes of seed coat colour in B. napus.

Effect of Mechanical-Transplanting Density on Lodging Resistance and Yield in Different Types of Rice

XU Jun-Wei,MENG Tian-Yao,JING Pei-Pei,ZHANG Hong-Cheng,LI Chao,DAI Qi-Gen,WEI Hai-Yan,GUO Bao-Wei

Acta Agron Sin. 2015, 41(11):  1767-1776.  doi:10.3724/SP.J.1006.2015.01767

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In order to study impacts of planting density of mechanical-transplanting rice on lodging resistance and yield, a field experiment was conducted using Indica-Japonica hybrid rice Yongyou 2640, Yongyou 1640 and Indica hybrid rice Fengliangyouxiang 1, Xinliangyou 6380 with six planting densities (A: 31.7 cm × 30 cm, B: 22.2 cm × 30.0 cm, C: 17.1 cm × 30.0 cm, D: 13.9 cm × 30.0 cm, E: 11.7 cm × 30.0 cm, F: 10.6 cm × 30.0 cm). The experimental results were as follows. With the increasing of transplanting density, the yield increased firstly and decreased then, with the highest yield at 13.9 cm × 30.0 cm, both for Indica-Japonica hybrid rice and Indica hybrid rice. The effects of densities on the two types of varieties were not entirely consistent. Under the densities of C–E, the yield of indica-japonica hybrid rice was higher than 10.5 t ha^-1, and little or no lodging occurred. Therefore, we could obtain high and stable yield. Under the density of D, the yield of indica hybrid rice was higher than 10.0 t ha^-1, and the apparent lodging rate was also higher, so it was difficult to obtain stable yield. With the increasing of transplanting densities, lodging index of two types of rice increased, and stem diameter, wall thickness of culm and dry weight of a unit internode in two types of rice decreased. With increasing filling time, lodging index of indica-japonica hybrid rice increased firstly and decreased then, with the peak value at 30 days after heading, wall thickness of stem, plumpness of internode and single stem weight decreased firstly and increased then, with a minimum value at 30 days after heading. Lodging index of indica hybrid rice was increasing, stem wall thickness was decreasing, plumpness of internode decreased firstly then decreased or increased slightly at 30 days after heading, but not obvious, single stem weight decreased firstly and increased then, with a minimum value at 30 days after heading. The sensitive period of lodging was around 30 days after heading.