Table of Content

12 February 2011, Volume 37 Issue 02

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REVIEW

Molecular Design Breeding in Crops in China

WANG Jian-Kang, LI Hui-Hui, ZHANG Hua-Cai, YIN Chang-Bin, LI Yu, MA Wei-Zhi, LI Xin-Hai, QIU Li-Juan, MO Jian-Min

Acta Agron Sin. 2011, 37(02):  191-201.  doi:10.3724/SP.J.1006.2011.00191

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Molecular design breeding is a highly integrated system built on multiple scientific disciplines and technological areas. It allows the simulation and optimization of the breeding procedure before breeders’ field experiments. Thus the best target genotypes to meet various breeding objectives in various ecological regions, and the most efficient and effective crossing and selection strategies approaching the best target genotypes can be identified. The design breeding greatly increases the predictability in conventional breeding, leading to the evolution from “phenotypic breeding by experience” to “genotypic breeding by prediction” and an increased breeding efficiency and effectiveness. Three major steps are involved in design breeding. The first step is to identify genes affecting breeding traits and to study gene and gene interactions, i.e., to seek for the original materials for producing the crop cultivars, which includes establishment of genetic populations, screening of polymorphism markers, construction of linkage maps, phenotypic evaluation and genetic analysis etc. The second step is to determine the target genotypes for various breeding objectives in various ecological regions, i.e., prototype of the final cultivar product, which includes the genotype-to-phenotype prediction based on identified and known gene information, i.e., locations of genes on chromosomes, biochemical pathways and expression networks from genes to traits, their genetic effects on breeding traits, and the interactions between genes. The third step is to identify the most efficient breeding strategies leading to the target genotypes determined in the second step, i.e., a detailed blue chart to produce the designed crop cultivars. Significant progresses have been made in crop molecular design breeding in China in recent years. This paper first summarized major progresses made in the development of novel genetic materials, genetic study of important breeding traits, development and application of breeding simulation tools, application of design breeding, and the platform research and development in molecular design breeding in crops in China. A perspective view of molecular design breeding was given for the near future after reviewing the current research both in China and worldwide. Finally, major research areas relevant to molecular design breeding in China were proposed, among which are prediction methods and tools of genetics and breeding, genetic mating designs and analysis, gene and environment interactions, functional genomics of crops, methods and tools of bioinformatics, technical systems and decision-supported tools. Professional development and education, and team building are essential as well to China’s leading role in crop molecular design breeding in the world.

Progress of Wheat Breeding in China and the Future Perspective

HE Zhong-Hu, JIA Xian-Chun, CHEN Xin-Min, ZHUANG Qiao-Sheng

Acta Agron Sin. 2011, 37(02):  202-215.  doi:10.3724/SP.J.1006.2011.00202

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During the last ten years, Chinese wheat breeding has mainly made progresses in three aspects, i.e., (1) two sets of cultivars with high yielding potential, improved quality, and multi-resistance to various diseases were developed and extended, (2) three elite parents, viz. Zhou 8425B, Lumai 14, and 6VS/6AL translocation line played a leading role in cultivar development; and (3) a significant progress has been achieved in breeding methodology and applied research. Main constrains on wheat breeding were also summarized. The development and utilization of molecular markers such as SSR marker and functional maker, was reviewed from breeding point of view, and the priority areas for the next five to ten years were proposed. It summarized the progress of wheat quality study which is closely associated with cultivar development, including laboratory evaluation methods and selection criteria for pan bread, cookie, Chinese noodles and steamed bread. China’s strategies for wheat breeding were analyzed in four areas: (1) a draft points on improving Chinese wheat yield potential; (2) utilization of durable resistance for cultivar development; (3) more efforts on water use efficiency, tolerance to high temperature and traits associated with broad adaptation due to the serious impact of climate change; and (4) increased investment in breeding and seed marketing from private sector.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Cloning and Characterization of GmAOS Gene and Its Promoter in Soybean (Glycine max)

WU Juan-Juan, WU Qian, YU De-Yue

Acta Agron Sin. 2011, 37(02):  216-223.  doi:10.3724/SP.J.1006.2011.00216

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Allene oxide synthase (AOS) is a major intermediate enzyme in octadecanoid pathway to JA biosynthesis affecting the synthesis and levels of all JA-related compounds in plants, and therefore plays a signi?cant role in plant defense.In this study, a full length cDNA of GmAOS and its promoter were cloned from the soybean (Glycine max) by RT-PCR, RACE, and LA PCR methods. GmAOS cDNA coding 519 amino acids (58.3 kD) with an isoelectric point of 8.97 and two genes copies in the soybean genome coding for GmAOS. Bioinformatics analysis indicated that the N-terminal region of GmAOS displayed features of a typical chloroplast targeting peptide including an enrichment of serine, threonine and tyrosine phosphorylation sites. The length of the promoter was 472 bp, containing several stress-induced elements: GA inducing elements (TAACAA), W-box element which was in response to elicitor-responsive transcription of defense genes, element responsive to salt and pathogen (GAAAAA) and G-box (CACGTG) induced by JA. Jasmonic acid showed a strong inducement of the GmAOS transcript level, expression patterns of GmAOS were explored in two soybean accessions with distinct resistance to cotton worm: XTDD was highly susceptible and HPXQD highly resistant, showing that GmAOS had higher transcript level in HPXQD(HR) than in XTDD(HS). GmAOS transcript level were correlated with soybean material resistance grades. These results suggest GmAOS is likely to be a useful tool for improving self-resistance abality of high plants.

Assessment of Genetic Diversity in Chinese Sorghum Landraces Using SSR Markers as Compared with Foreign Accessions

ZHANG Han, WANG Jian-Cheng, WANG Dong-Jian, TAO Feng-Xia, HU Jin-Fang, SONG Guo-An, GUAN Yan-An, LI Ru-Yu

Acta Agron Sin. 2011, 37(02):  224-234.  doi:10.3724/SP.J.1006.2011.00224

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The genetic variation of 184 Chinese sorghum landraces (Sorghum bicolor L.) from a broad geographic area and representing different phenotypes, and 69 representative foreign cultivated sorghum accessions (world sorghum), was assessed using 32 nuclear SSR primer pairs. Overall, lower level of genetic diversity was detected in Chinese sorghum than in world sorghum. The allelic richness (Rs) and Nei’s allele diversity (He) for Chinese sorghum and world sorghum were 9.81 and 0.629, and 11.52 and 0.745, respectively. Fewer unique alleles were detected in Chinese sorghum than in world sorghum. Chinese sorghum had a genetic diversity level lower than accessions from East Africa (He=0.732), North America (He=0.707) and South Asia (He=0.712); and was only comparable to those from South African accessions (He=0.609). Marked differences in level of genetic variation were revealed between Chinese sorghum landraces from 12 provinces, with Rs ranging from 3.64 to 4.88 and He from 0.517 to 0.714. Accessions from Jilin Province exhibited the highest level of genetic diversity among all regions in China, which was comparable to the sorghum in East Africa . The results indicated a strong divergence of Chinese sorghum from world sorghum, but a weak differentiation among Chinese sorghum both on regional and type bases. Principal component analysis (PCA) clearly separated Chinese sorghum from world accessions but could not separate Chinese sorghum into discrete geographical or phenotypic groups. Analysis of molecular variance (AMOVA) indicated that 20.43% of the total genetic variation was attributable to the difference between world and Chinese sorghum and 79.57% occurred among Chinese and world sorghum accessions. For Chinese sorghum, partitioning the total variation revealed that genetic diversity mainly existed among accessions within regions (91.94%) or eco-regions (94.97%) rather than among regions (8.06%) or eco-regions (5.03%). Similarly, a large portion (97.93%) of the total variation was found within types compared to among types (2.07%). Our study supports the view that Chinese sorghum is of African origin. Chinese sorghum may have experienced a long history of natural and human selection when largely isolated from outside world since prehistoric time. Suggestions for sorghum breeding programs were presented in the light of these data.

QTL Mapping of Ear Traits of Maize under Different Water Regimes

TAN Wei-Wei, LI Yong-Xiang, WANG Yang, LIU Cheng, LIU Zhi-Zhai, BANG Bo, WANG Di, ZHANG Yan, SUN Bao-Cheng, DAN Yun-Su, SONG Yan-Chun, YANG De-Guang, WANG Tian-Yu, LI Yu

Acta Agron Sin. 2011, 37(02):  235-248.  doi:10.3724/SP.J.1006.2011.00235

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Ear traits are closely associated with maize yield. Therefore, genetic dissection of ear traits can provide clues to maize high-yield breeding and is especially important in breeding for drought tolerance. In this study, seven ear related traits including ear length (EL), ear diameter (ED), row number (KRN), kernel number per row (KRE), grain yield per ear (GW), cob diameter (AD) and weight per ear (EW), were investigated using two sets of F_2:3 populations, which were derived from crosses of Ye478×Huangzaosi (Y/H) and Qi319×Huangzaosi (Q/H), respectively. The two populations were evaluated under different water conditions in Xinjiang in 2007 and 2008. The results showed that those ear traits under drought were phenotypically lower than those under normal water regime and ear length, ear diameter, weight per ear had positive correlation with GW. A total of 75 QTL were identified under different water regimes using mixed linear model with two methods of single-experiment analysis and water regime joint analysis, including 20 QTL detected under normal water regime and 55 QTL detected under drought stress. The QTL detected in Y/H were located on chromosome 1, 2, 5, 6, 7, and 10, and the QTL detected in Q/H were distributed on chromosome 2, 3, 4, 5, 6, 7, 9, and 10. However, only four and nineteen QTL was identified in the two populations under drought stress respectively, significantly lower than that detected under normal water regime. Meanwhile, in the joint analysis, only three QTL had significant interaction with environments and six QTL had epistatic interaction, showing that the genetic feature of ear traits was complex. In Y/H, two congruent QTL, qKRE1-5-1 and qKRE1-7-1, were detected under different water levels, with the phenotypic contribution from 6.15% to 19.48%, while in Q/H, three congruent QTL, qKRE2-5-1, qGW2-10-1, and qKRE2-3-1, were detected under different water levels, with the phenotypic contribution from 7.14% to 16.65%. These results implied that these QTL were little influenced by environment and could stably expressed, which can be used in marker-assisted selection.

QTL Analysis of Oil Content Difference in Two Environments in Brassica napus L.

LI Chao, LI Bei, QU Cun-Min, YAN Xing-Ying, FU Fu-You, LIU Li-Zhao, CHEN Li, LI Jia-Na

Acta Agron Sin. 2011, 37(02):  249-254.  doi:10.3724/SP.J.1006.2011.00249

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According to the genetic linkage map established by our laboratory and composite interval mapping (CIM), the QTLs oil content difference between two environments were detected using the recombinant inbred lines (RIL) SWU-1 and SWU-2in Brassica napus L.two QTLs of the oil content difference were located in the two linkage groups, each of the QTLs explained 10.31%–12.45% of phenotypic variation in SWU-1; three QTLs of the oil content difference were located in the two linkage groups, each of them explained 6.60%–10.58% of phenotypic variation in SWU-2. The results showed that the oil content difference of the different genotypes was quite different, ranging from 0 to 18.66% and the coefficient of variation was up to 58.24%, which means there are different environment insensitive genes for oil content in the different genotypes. There wereno visiblelinkage relationship between the QTLs of oil content difference and the QTLs of oil content in two environments, which indicated that sensitive and insensitive genes do not have the same genetic expression system as the oil synthesis genes.

Identification of a High-Yield Introgression Locus from Synthetic Hexaploid Wheat in Chuanmai 42

LI Jun, WEI Hui-Ting, HU Xiao-Rong, LI Chao-Su, TANG Yong-Lu, LIU De-Cai, YANG Wu-Yun

Acta Agron Sin. 2011, 37(02):  255-262.  doi:10.3724/SP.J.1006.2011.00263

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Synthetic hexaploid wheat, a carrier of many elite genes, is an important genetic resource in the improvement of common wheat (Triticum aestivum L.). Chuanmai 42 is a wheat cultivar with high-yield potential and resistance to strip rust(Puccinia striiformis f. sp. tritici), which was developed by crossing and backcrossing Syn769 (an elite synthetic hexaploid wheat) with Sichuan commercial wheat cultivars. For understanding the genetic effects of the introgression loci of synthetic hexaploid wheat in Chuanmai 42, a total of 78 introgression loci of synthetic hexaploid wheat were identified in Chuanmai 42 by scanning using 1029 SSR markers. Using 127 recombinant inbred lines (RILs, F₈) with Chuanmai 42 (introgression loci) and Chuannong 16 (Chuannong 16 loci) backgrounds, the genetic effects of the introgression loci were evaluated across six environments in Sichuan Province, China from 2006 to 2009. One high-yield potential locus Barc1183 derived from the synthetic hexaploid wheat was detected in Chuanmai 42. It was further located on the long arm of 4D chromosome using the 4DS and 4DL telosomic lines of Chinese Spring and the 4D(4A) and 4D(4B) substitution lines of Longdon. This locus had positive effects on increasing tiller number per plant, number of effective spikes, grain number per square meter, harvest index, and grain production rate, and the average yield was increased by 8.92% compared with Chuannong 16 in the six growing environments. Therefore, the introgression locus Barc1183 of synthetic hexaploid wheat can be useful for breeding high-yield potential wheat.

Evaluation of Resistance to Sheath Blight (Rhizoctonia solani) in Some Indica Hybrid Rice from Southern China

WANG Ling, HUANG Wen-Wen, LIU Lian-Meng, FU Qiang, HUANG Shi-Wen

Acta Agron Sin. 2011, 37(02):  263-270.  doi:10.3724/SP.J.1006.2011.00263

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Rice sheath blight caused by Rhizoctonia solani is one of the most devastative diseases worldwide, which causes serious yield loss under favorable environmental conditions. R. solani has a very wide host range and the rice germplasm with complete resistance to this disease is zezo. Sheath blight resistance is generally controlled by polygene, with a wide variation among rice cultivers. It is necessary to evaluate probably partial resistance to sheath blight from germplasms for rice breeding program. A total of 166 indica hybrid rice combinations collected from 11 provinces in southern China were inoculated by using five isolates with different pathogenicities at seedling stage in the greenhouse. No combination was found to be completely immune or highly resistant, and the resistance to sheath blight varied significantly among different combinations. Average disease index of these combinations were in accordance with normal distribution N (5.27, 0.68²) and ranged from 2.84 to 7.64. The results showed that this inoculation method at seedling stage was simple, rapid, uniform, and allowed to distinguish minor differences in susceptibility, so it can be used for a large-scale screening or primary resistance identification. According to the disease index of each isolate, 166 combinations were classified into five types based on dynamic clustering analysis (DCA), namely resistant (R), moderately resistant (MR), moderately susceptible (MS), susceptible (S) and highly susceptible (HS), accounting for 1.20%, 13.86%, 36.14%, 43.37%, and 5.42%, respectively. The discriminant functions for each type were calculated based on Bayes method, and the accuracy rate for discrimination reached 96.39%. The results indicated that most of the combinations were susceptible. Only two combinations, K you 88 and Zhongyou 9801, were resistant, but should be verified at the adult stage in paddy field. Synthetic disease index (SDI) of all combinations was also calculated by average disease index of the five isolates, the combinations were graded as R, MR, MS, S, and HS based on SDI, accounting for 1.20%, 13.25%, 63.25%, 21.69%, and 0.60%, respectively. There was significant correlation between the results of DCA and SDI (r = 0.81, P < 0.01), showing that both methods can be used for evaluating the disease resistance. But the former method is suitable for seedling screening under the uniform growth conditions; while the latter is independent of time, place and batch of the identification, and more versatile than the former. Only 26 combinations with resistance or moderate resistance to sheath blight were gained by DCA and SDI, the genetic distances ranged from 0.04 to 0.71. Twenty six combinations were divided into two groups by UPGMA cluster analysis, and 22 out of them were grouped into a group with the narrow genetic background at genetic distance of 0.36. There was a close relationship among the parents of the 26 combinations according to the pedigree tracing. Therefore, the practical strategy for rice resistance breeding to sheath blight is further to broaden genetic bases of germplasm, pyramid quantitative resistance genes, construct hybrid combinations with parents having desirable traits and resistance to sheath blight.

Detection of Quantitative Trait Loci for Plant Height in Different Photoperiod Environments Using an Immortalized F₂ Population in Maize

WANG Cui-Ling, SUN Chao-Hui, KU Li-Xia, WANG Tie-Gu, CHEN Yan-Hui

Acta Agron Sin. 2011, 37(02):  271-279.  doi:10.3724/SP.J.1006.2011.00271

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For studying the genetic basis of plant height in maize, an immortalized F₂ population of 278 F₁ cross was constructed by intercrossing recombinant inbred lines derived from a cross between temperate and tropical inbred lines (Huangzaosi × CML288). The “immortalized F₂” was evaluated for plant height in five locations with three photoperiod environments, i.e. a short day environment of Sanya in Hainan province, long-day environments of Zhengzhou and Luoyang in Henan province, and long-day environments of Shunyi and Changping in Beijing. Twelve QTLs for plant height were detected in different photoperiod environments using composite interval mapping. The QTLs qPH1-2 and qPH4 associated with plant height were detected in all the three photoperiod environments, showing that these two QTLs might control plant height steadily in different environments. The QTL qPH3 was detected for plant height and explained 32.13% of the phenotypic variation in short day environment while could not be detected in long day environment, which indicated that the QTL qPH3 might control plant height only in short day environment. The QTL qPH10-1 in the bin 10.04 region of chromosome 10 associated with plant height was detected in long day environments of Henan and Beijing and explained 25.39% and 39.58% of the phenotypic variation, respectively. This result indicated that the QTL qPH10-1 might be a major plant height QTL in long day environment.

Characterization and Gene Mapping of a Spikelet Mutant multi-floret 1(mf1) in Rice

LI Yun-Feng, YANG Zheng-Lin, LING Yang-Hua, WANG Nan, REN De-Yong, WANG Zeng, HE Guang-Hua

Acta Agron Sin. 2011, 37(02):  280-285.  doi:10.3724/SP.J.1006.2011.00280

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 Rice has a determinate spikelet producing a fertile floret above two sterile lemmas. In this study, we reported a multi-floret 1 (mf1) mutant, in which spikelet lost the determinacy and produced two or more florets in an alternate phyllotaxy above sterile lemmas. In addition, all the florets showed the defects of floral organs development, such as the elongated leafy lemma, and decreased lodicule/stamen. Genetic analysis indicated that the mf1 trait is controlled by a single recessive gene. By bulked segregation analysis (BSA) and rice SSR molecular maker, the mf1 locus was located between PSSR3 and RM7576 on chromosome 3 with a 34 kb physical distance containing four annotated genes. This result provided a foundation of map-based cloning and function analysis of MF1 gene.

Cloning of Cotton CBF Gene and Its Cold Tolerance Expression in Transgenic Tobacco

GUO Hui-Meng, LI Shao-Chun, ZHANG Han, XIN Yue-Zhi, CHENG Hong-Mei

Acta Agron Sin. 2011, 37(02):  286-293.  doi:10.3724/SP.J.1006.2011.00286

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Low temperature is an adverse environment condition affecting the growth and productivity of crops, it is also one of limiting factors for cotton yeild and quality in China.CBF is a kind of transcription factor that can regulate expression of a number of genes related with abiotic stresses. Therefore, it is important to study the characteristics of cotton CBFs and their response to abiotic stresses. In this study, CBF gene was isolated from the genomic DNA of cotton cultivars Gh12, Gh36 and Gb7124. Cotton CBF gene encodes 184 amino acids, containing CBF-family signature “PKRRAGRKKFQETRHP” and “FADSAW”. Southern blotting result showed that CBF genes were presented as the form of gene family in the genome of cotton. Northern blotting result indicated that GbCBF1 gene was induced by low temperature, drought, salt and ABA. GbCBF1 was constructed into plant expression vector pCambia2301, in which the gene was driven by 35S and NOS promoters separately. Plant expression vectors were then transferred into tobacco NC89 using Agrobacterium-mediated transformation method. Twenty six trangentic tobacco lines were obtained after kanamycin screening and PCR detection. PCR and Reverse tanscription PCR methods were used to analyze part of T₁ transgenic tobacco, the results showed that GbCBF1gene could be transcripted and inherit in offspring normally. The analytical result demonstrateted that the electrolytic leakage rate of transgenic tobacco was lower than that of wild type tobacco generally, however, free proline content and soluble sugar content of transgenic tobacco were higher than those of wild type tobacco under low temperature stress. In conclusion, GbCBF1 enhances cold tolerance in transgenic tobacco.

QTL Mapping for Coleoptile Length and Radicle Length in Wheat under Different Simulated Moisture Stresses

YUAN Qian-Qian, LI Zhuo-Kun, TIAN Ji-Chun, HAN Chu-Xiao

Acta Agron Sin. 2011, 37(02):  294-301.  doi:10.3724/SP.J.1006.2011.00294

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Coleoptile length and Radicle length are the important indexes to evaluate resistance of wheat (Triticum aestivum L.) seedlings to stresses. For mapping quantitative trait loci (QTLs) for lengths of coleoptile and Radicle in wheat, a set of immortalized F₂ (IF₂) population (168 lines) from Huapei 3 ´ Yumai 57 double haploid (DH) lines was treated with distilled water (normal condition) and 10%, 20%, and 30% of polyethylene glycol (PEG-6000). The coleoptile length (CL) and radicle length (RL) of the parents and the 168 IF₂ lines were measured after 7 d of treatment. QTLs for CL and RL were detected using 323 SSR markers, which were distributed in the whole genome of wheat. Based on inclusive composite interval mapping (ICIM) method, we identified 11 additive QTLs for CL and 12 additive QTLs for RL under normal and the three stress conditions. Each locus explained 4.93%–35.37% of phenotypic variance. In the interval between Xcfd39.2and Xcfd22.2on chromosome 4B, QTL QCl4B had the phenotypic contribution of 35.37%. Another QTL QCl3D-a located between Xcfd223 and Xbarc323 on chromosome 3D was detected in both normal and 20% PEG-6000 treatments, and explained phenotypic variances of 7.83% and 11.74%, respectively. QTL QCl3D-b was located on the same chromosome and close to QCl3D-a. In the linkage groups 1A and 5A1, three and two QTLs associated with RL were detected respectively. On chromosome 6D, two QTLs for CL and RL were found in the interval between Xswes679.1 and Xcfa2129 and the interval between Xwmc412.1and Xcfd49, respectively. The major QTLs identified can be applicable in marker-assisted selection in wheat breeding for coleoptile and root.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Asymmetric Warming on Contents and Components of Starch and Protein in Grains of Winter Wheat under FATI Facility

TIAN Yun-Lu, CHEN Jin, DENG Ai-Xin, ZHENG Jian-Chu, ZHANG Wei-Jian

Acta Agron Sin. 2011, 37(02):  302-308.  doi:10.3724/SP.J.1006.2011.00302

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Climate warming presents significantly asymmetric trends with greatly seasonal and diurnal differences, greater temperature elevations existing in the winter-spring season than in the summer-autumn season and at the nighttime than at the daytime. To date, this is till lack of evidence about the effects of asymmetric warming on the quality of winter-wheat grain based on field experiments. Here, we performed field warming experiment under free air temperature increased (FATI) facility to investigate the impacts of asymmetric warming on the contents and components of starch and protein in winter-wheat grain during 2007-2009 in Nanjing, Jiangsu province, China. The results showed that the all-day warming (AW), daytime warming (DW), and nighttime warming (NW) treatments significantly advanced the grain-filling stage and changed the appearance time and days of high temperature above 32°C in grain-filling stage, consequently resulting in obvious changes of starch component, protein content and protein components. Treatments AW, DW, and NW had no significant impact on the starch content of winter-wheat grain but tended to increase the ratio of amylose content to amylopectin content. The highest values of the ratio of amylose content to amylopectin content existed in the DW plots which were 6.9% and 46.2% higher than those in the control plots in the two years, respectively. The content of grain protein was significantly decreased by warming with the content order of CK > DW > NW > AW. Warming decreased the grain protein contents by 9.1%, 5.4%, and 6.9%, respectively in the AW, DW, and NW treatments on average of the two years. The effects of warming on grain protein components were complicated. However, DW showed a regular impact on protein components. The two-year result showed that the lowest content of albumin and the greatest content of globulin occurred in the DW plot with a lowest ratio of glutelin content to gliadin content. All these results demonstrate that the effects of asymmetric climate warming on the quality of winter-wheat grain are complicated with significant differences among warming patterns and experimental years.

Tillering Characteristics and Its Relationships with Population Productivity of Super Rice under Different Cultivation Methods in Rice-wheat Cropping Areas

LI Jie, ZHANG Hong-Cheng, GONG Jin-Long, CHANG Yong, WU Gui-Cheng, GUO Zhen-Hua, DAI Qi-Gen, HE Zhong-Yiang, XU Ke, WEI Hai-Yan

Acta Agron Sin. 2011, 37(02):  309-320.  doi:10.3724/SP.J.1006.2011.00309

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To explore tillering characteristics and its relationships with population productivity of rice under different cultivation methods in the rice-wheat cropping system in the lower Yangtze River, we compared the characteristics of rice tillering and panicle formation and its productivity and contribution to yield with two super rice cultivars Huaidao 9 and Xudao 3 by using three cultivation methods, precisionartificial transplanting with dry nursery middle and strong seedlings, mechanical transplanting with small seedlings and direct seeding. Results showed that rice yields by using different cultivation methods were significantly different, artificial transplanting rice was highest, while direct seeding rice was lowest. The great contribution to yields of mechanical transplanting rice and direct seeding rice were mainly from main stem and primary tillers group, in particular for the direct seeding rice, the proportion of stem yield was up to 27.5%, that of secondary tillers group only about 5%. However, for artificial transplanting rice the stem yield proportion was small (16.7%), yield of secondary tillers group accounted for nearly 20%. The proportion of primary tillers group yield was relatively stable among the different cultivation methods and it ranged from 65.84% to 67.09%. The number of tiller leaf position of artificial transplanting rice was more, earbearing tiller percentage was higher and panicle number per plant was more. The primary tillers group emerged from leaf 1 to leaf 10 on main stem, among them the tillers from leaf 5 to leaf 8 leaf had higher emerging rate and more panicles, secondary tillers groupemerged and earbeared mainly in 1/5,1/6,1/7. Tillers of mechanical transplanting rice had a more concentrated emergence, the primary tillers group emerged from leaf 3 to leaf 7 on main stem, among them leaves 4 to 7 were the superior positions for tiller emerging and panicle formation, secondary tillers groupemerged mainly in 1/4, 2/4, 1/5, but earbeared mainly in 1/4. The primary tillers group of direct seeding rice emerged from leaf 1 to leaf 5 on main stem, among them the leaf positions of 1 to 4 had higher rate of tiller emerging and panicle formation, secondary tillers emerged more, but earbeared only in 1/1, 2/1, 1/2, with a very low earbearing percentage. These three cultivation methods did not give tillering three times and more than three times. The tillers group of main stem and superior leaf positions in each cultivation method had higher population productivity and better panicle traits, made great contributions to the yield, and more than 85% of the yield came from these stems and tillers. The results suggested that the tillering and panicle formation law by different cultivation methods is different. It is indicated that increasing percentage of earbearing tiller and panicle number per plant and playing regulation fully of tillers group will improve the yield. In rice production,we should enhance the superior leaf position tillers’ emergence and flowering frequency, inhibit invalid tillers, improve the population quality, explore the way to increase yield potential of the superior leaf position by using the consequentially supporting management measures and through the precise regulation of fertilizer application and irrigation based on the actual various cultivation methods, consequently, achieve the target of high yield and efficient production under different cultivation methods.

Dynamic Characteristics of Leaf Area Index in Maize and Its Model Establishment Based on Accumulated Temperature

LI Xiang-Ling, ZHAO Ming, LI Cong-Feng, GE Jun-Zhu, HOU Hai-Peng

Acta Agron Sin. 2011, 37(02):  321-330.  doi:10.3724/SP.J.1006.2011.00321

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In order to clarify the demand of accumulated temperature in the growth process of maize cultivars of different maturities and the relationship between leaf area index and accumulated temperature. Three cultivars used (Yinong 103, Xianyu 335, and Denghai 661) were carried, with three sowing dates (May 3rd, May 28th, and June 22nd) and four density treatments (45 000 plants ha^-1, 60 000 plants ha^-1, 75 000 plants ha^-1, and 90 000 plants ha^-1). The dynamic characteristics of leaf area index were measured and the model based on accumulated temperature were established. The largest LAI and accumulated temperature from emergence to maturity were normalized, and the six main models were compared. Results show that, the Ration equation y=(a+bx)/(1+cx+dx²) had a good simulation results and would be used significantly in biological applications, the equation was y=(-0.05247+1.2766x)/ (1-2.6346x+3.6359x²), r = 0.9479^**, where is relative seedling groups LAI, (a+ b)/(1+c+d) is the relative maturity groups LAI.The values of a and c had a slightly difference, however, the values of b and d changed dramatically among sowing dates and among varieties, and a small difference among densities, showing that sowing dates changed the LAI mainly through the values of b and d in maize. The accuracy and precision of the normalized model were tested with the data of 2008 and the data of 2007 in Huadian, Jilin, the simulation accuracy (k) was all above 0.9392^**, and the precision (R²) was all above 0.9996^**.  Sowing dates regulated the growth days, average temperature, accumulated temperature, average LAI, change rate of LAI and grain yield in different maturity cultivars of maize, when the sowing date delayed, the growth days, accumulated temperature, the average LAI and grain yield were all decreased, the average temperature was increased.The growing days and accumulated temperature showed as Denghai 661> Xianyu335> Yinong 103, grain yield and average LAI showed as Xianyu335 > Denghai 661 > Yinong 103.

Starch Physicochemical Characteristics and Granule Size Distribution at Apical, Middle and Basal Ear Positions in Normal, Sweet, and Waxy Maize

LIU Da-Lei, GUO Huan-Fen, DONG Ce, LIU Wei-Beng

Acta Agronomica Sinica. 2011, 37(02):  331-338.  doi:10.3724/SP.J.1006.2011.00331

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The starch physicochemical characteristics and granule size distribution at different ear positions (apical, middle, and basal) were studied using normal, sweet, and waxy maize. The results indicated that values of viscosity characteristics for sweet maize starch were higher at apical position. Normal maize starch peak viscosity (PV) and breakdown (BD) were higher at apical position; while setback (SB) was similar for three positions. Waxy maize starch presented the highest BD at apical position; while PV and SB were similar for three positions. The transition temperature (onset-, peak-, and conclusion temperatures) was higher at basal position for sweet maize, similar among three positions for normal maize, and higher at middle position for waxy maize. The change tendency for the enthalpy of gelatinization among three ear positions was different for three types of maize. Starch granule volume distribution frequency showed a typical two-peak curve. The percentage for starch granule diameter higher than 17 μm was the lowest at apical position and the highest at middle position. Iodine binding capacity was similar among three positions for waxy maize, whereas it was the lowest at apical position for sweet and normal maize. Correlations of starch granule volume distribution and iodine binding capacity with pasting and thermal characteristics indicated that the differences for pasting and thermal characteristics among different ear positions were resulted from the differences for starch granule size distribution and chain-length.

Effect of Postponing N Application on Yield, Nitrogen Absorption and Utilization in Super-High-Yield Summer Maize

WANG Yi-Lun, LI Chao-Hai, TAN Jin-Fang, ZHANG Hu, LIU Tian-Hua

Acta Agron Sin. 2011, 37(02):  339-347.  doi:10.3724/SP.J.1006.2011.00339

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Maize (Zea mays L.) is the largest grain crop in China. Realizing super-high-yield (≥12 000 kg ha^-1) of summer maize plays an important role in ensuring the country food security. However, there exist some problems in summer maize production such as excessive dosage and unreasonable period of nitrogen application, which hinders the realization of super-high-yield. In order to increase the use efficiency of fertilizer and grain yield of summer maize, field experiments were conducted and the effects of postponing N application on nitrogen absorption, use efficiency of nitrogen fertilizer and grain yield in summer maize were studied. The results showed that yield was increased by 9.62%–15.95% by applying nitrogen fertilizer. Compared with conventional fertilizer application, postponing N application increased grain yield by 2.27%–5.33%. The N absorption proportion after silking stage was 40.30%–47.78% of the total, so it is important to provide maize plants with sufficient N in later growth stage for realizing super-high-yield. It was indicated that postponing N application could promote N absorption and accumulation of super-high-yield summer maize at later stage, decrease N transfer efficiency in stem and leaf, increase activity of nitrate reductase and content of free amino acids in ear leaf at filling stage, and raise protein yield of summer maize. In comparison with conventional fertilizer application, the N fertilizer utilization rate and N fertilizer agronomy efficiency were increased by 1.88%–9.70% and 0.96–2.21 kg kg^-1 respectively by postponing N application. The highest yield and nitrogenous fertilizer use efficiency were obtained by applying 30% of nitrogen fertilizer at seedling stage and trumpeting stage respectively and 40% of nitrogen fertilizer at silking stage.

Comparison and Screening Indicators for Ramie (Boehmeria nivea) Genotypes Tolerant to Cadmium

SHE Wei, HE Yu-Cheng, GENG Hu-Cheng, LU Yan-Wei, HUANG Meng, KANG Mo-Li, WANG Dong

Acta Agron Sin. 2011, 37(02):  348-354.  doi:10.3724/SP.J.1006.2011.00348

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The rapid industrialization causes the large areas of heavy metal contaminated soils, which has become a threat to the local ecosystems. Cadmium (Cd) is a heavy metal which has aroused great concerns in the environmental science community, because of its toxicity to animals and humans. Screening and breeding high cadmium tolerant ramie genotype is one of the effective alternatives to utilize the cadmium contaminated soil, since ramie could minimize the potential hazard of bringing toxic metals into food chains.In this study, a hydroponic culture experiment and a field micro-plot trial were carried out tocompare nine ramie genotypes and their respective screening indices for Cd tolerance. In the hydroponic culture experiment, substantial differences and significant genotypic variations in plant height, leaf number per plant, shoot dry weight and root dry weight were found in different Cd treatments. The shoot dry weight well correlated with plant height, SPAD of leaf and root dry weight. In the field trial, the shoot dry weight well correlated with plant weight, diameter of stem and thickness of bark. This suggests that these characteristics could be used as Cd tolerance indicators. Cluster analysis using comprehensive Cd tolerance characteristics as evaluation parameters indicated that nine genotypes were divided into three categories. These results suggested that it would probably be an effective method to use the plant height, SPAD of leaf, shoot dry weight and root dry weight in ramie hydroponic culture experiment with different Cd treatments as selection indicators.

Dry Matter Production and Photosynthesis Characteristics of Three Hybrids of Maize (Zea mays L.) with Super-High-Yielding Potential

YANG Jin-Shing, WANG Yong-Jun, ZHANG Ji-Wang, LIU Peng, LI Cong-Feng, ZHU Yuan-Gang, HAO Meng-Bei, LIU Jing-Guo, LI Deng-Hai, DONG Shu-Ting

Acta Agron Sin. 2011, 37(02):  355-361.  doi:10.3724/SP.J.1006.2011.00355

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The plant height and ear height are the important factors affecting the grain yield in maize (Zea mays L.) which determined the planting density. Obviously, it is essential for high yield to explore the dry matter production and photosynthesis characteristics of super-high-yielding potential hybrid maize with different plant heights and ear heights. Therefore, a field experiment with 82 500 plant ha^-1 was conducted to evaluate the three hybrids (Denghai 661, DH661, the low-plant height and low-ear height; Denghai 701, DH701, the medium-plant height and medium-ear height; Xianyu 335, XY335, the high-plant height and high-ear height). The biomass, leaf area index (LAI), potential photosynthetic capacity (LAD), gas exchange parameters (light-saturated photosynthetic rate-P_sat, stomatal conductance-g_s and intercellular CO₂ concentration-C_i) and chlorophyll fluorescence parameters (maximal efficiency of PS2 photochemistry-F_v/F_m, PS2 efficiency-Φ_PSII and photochemical quenching co-efficient-q_P) were determined. Yields of the three-type hybrids were over-15 000 kg ha^-1, but there were no significant differences among the three hybrids under conventional planting conditions. The results analyzed by Richards model showed that DH661 had the highest yield potential among the three hybrids because its active growth period was about three weeks longer than that of XY335. The yield potential of DH661 was remarkably high from 28 d after anthesis to harvest stage since it remained the higher photosynthesis capability and radiation utilization efficiency, but that of XY335 decreased rapidly.

RESEARCH ACTIVITIES

Isolation and Expression Analysis of Two GhBlind Homologs in Upland Cotton (Gossypium hirsutum L.)

XIONG Guan-Jun, XU Qin, HUA Jin-Ping

Acta Agron Sin. 2011, 37(02):  362-368.  doi:10.3724/SP.J.1006.2011.00362

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In higher plants, Blind homologs play an important role in plant architectures. Two Blind orthologs, GhBlind1 and GhBlind2, were isolated from cDNA of the shoot apex of upland cotton (Gossypium hirsutum L.) by homologous cloning strategy. GenBank accession number is HQ115643 for GhBlind1, and HQ115644 for GhBlind2. Similar to other Blind homologs, GhBlind1 and GhBlind2 were consisted of three exons and two introns, and encoded 359 and 262 amino acids, respectively. Based on the RT-PCR analysis, it was found that GhBlind1 expressed in root, leaf, and tender fiber, and predominantly in shoot apical meristem (SAM) and shoot apex, but not in stem; while GhBlind2 expressed in root, stem, leaf, SAM and shoot apex, but not in tender fiber. Using recombinant PCR technology, expression vectors Psuper-gus-b1 and Psuper-gus-b2 were constructed and used for Agrobacterium-mediated transient expression by transformation of embryogenic callus of upland cotton cv. Coker 201. Histochemical assays of GUS activity showed that after co-cultivation of embryogenic callus for four days, positive events were more obvious in Psuper-gus-b2 than in Psuper-gus-b1. The alignments between GhBlind1, GhBlind2 and the domain of Blind homologs showed the identities of 94% and 91%, respectively. The results of phylogenetic tree showed that GhBlind1 and GhBlind2 were genetically divergent from most of the other R2R3-MYB members in Gossypium hirsutum L. We speculated that GhBlind1 and GhBlind2 are probably related with the development of lateral branch in upland cotton.

RESEARCH NOTES

Optimization of Extraction Method and Two-Dimensional Electrophoresis Conditions for Proteome Analysis of Jute Functional Leaf

CHEN Fu-Cheng, QI Jian-Min, XU Jian-Tang, CHEN Tao, TAO Ai-Fen, LIN Pei-Qing, CHEN Mei-Xia, GUO Ying, LI Hua-Li

Acta Agron Sin. 2011, 37(02):  369-373.  doi:10.3724/SP.J.1006.2011.00369

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The protein extraction methods and electrophoresis conditions are the key facts of two-dimensional electrophoresis in proteomics. In this study, in order to set up a suitable method for jute leaf total protein extraction and the optimized condition for two-dimensional electrophoresis, we compared the protein extraction methods using TCA acetone, Tris-base acetone and Tris-HCl. We also optimized the sample loading amount and sample preparation approach. The results showed that protein productivity reached 79.0 mg g^–1 at most by TCA acetone method, and 44.2% and 114.1% higher than by other two methods, respectively. Besides, the 2-DE image background was the clearest and the protein spots were the most reaching about 602 by TCA acetone method, which is much more suitable as extraction method for jute leaf protein two-dimensional electrophoresis. The most suitable sample loading quantity was 350 mg, which lays a foundation for further study of jute proteomics. The construction of two-dimensional electrophoresis system can be use to study the differences of protein expression on normal material and mutant of jute, and promote the application of proteomics in jute mutant.

Cloning of Medicago sativa Phychrome B cDNA and Establishment of Its RNA Interference Expression Vector

SHU Jian-Meng, YAN Hua-Bing, SHI Ying-Hua, WANG Cheng-Zhang

Acta Agron Sin. 2011, 37(02):  374-379.  doi:10.3724/SP.J.1006.2011.00374

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The short day is one of the main factors affecting alfalfa fall dormancy, which is called as the photoperiodic effect. Study on the relationship between the main photoreceptors-PhyB gene and alfalfa fall dormancy may reveal the regulation mechanism of alfalfa fall dormancy radically, and provide a scientific reference for the application of alfalfa varieties differing in fall dormancy in forage production. The objective of this study was to establish an RNAi expression vector harboring PhyB gene of Medicago sativa. Two pairs of specific primers containing different enzyme sites were designed on the basis of PhyB gene sequence of alfalfa variety “Vernal” (GenBank accession number: GQ379903.1). With the template of total RNA, positive sense strand and antisense strand were amplified by RT-PCR and cloned into pGEM-T Easy vector to obtain recombinant vectors pGEMB-1 and pGEMB-2, then based on the intermediate vector pHANNIBAL and the plant binary expression vector pART27, we constructed the RNAi expression vector pART27-RNAi containing a hairpin structure by many times of enzyme digestion and connection. The results provide a foundation for further studying the relationship between alfalfa dormancy and PhyB.