Table of Content

12 March 2008, Volume 34 Issue 03

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Transformation of Wheat Thaumatin-Like Protein Gene and Diseases Resistance Analysis of the Transgenic Plants

XING Li-Ping;WANG Hua-Zhong;JIANG Zheng-Ning;NI Jin-Long;CAO Ai-Zhong;YU Ling;CHEN Pei-Du

Acta Agron Sin. 2008, 34(03):  349-354.  doi:10.3724/SP.J.1006.2008.00349

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The thaumatin-like protein in plants, an important member of pathogenesis-related proteins (PRs), involves in plant resistant reaction to many fungi. A series of thaumatin-like protein genes have been isolated and transformed to potato(Solanum tuberosum L.), rice (Oryza sativa L.), and wheat (Triticum aestivum L.) resulting in resistance improvement to plant diseases. We have cloned a thaumantin-like protein gene, Ta-Tlp, from wheat in our earlier studies. The Ta-Tlp gene expresses in high level in wheat 6VS/6AL translocation line with high resistance to powdery mildew (Erysiphe graminis f.sp. tritici Em. Marchal.), implying its close relation to the resistance of the disease. To further understand the gene’s function, we constructed Ta-Tlp into a expression vector driven by the strong ubi promoter in the present study. The constructed vector pAHC-TlP was transformed into immature embryo-derived calli of a common wheat cultivar Yangmai 158 through particle bombardment. After two rounds of herbicide bialaphos selection and regeneration, herbicide-resistance plants were obtained. The Ta-Tlp was confirmed having been integrated into the wheat genome and expressed in T1 and T2 generations by PCR, Southern blot, and RT-PCR. The transgenic plants of T0, T1, and T2 generations were inoculated by E. graminis f.sp. tritici and F. graminearum for resistance identification. All plants of T0, T1, (183 individuals derived from 6 positive T0 lines), and T2 (241 individuals derived from 6 positive T0 lines) generations appeared some resistance to wheat powdery mildew by delaying disease development, but no distinct resistance to scab (F. graminearum).

Molecular Characterization of

FANG Ti-Lin;CHENG Ying;LI Gen-Qiao;XU Shi-Chang;XIE Chao-Jie;YOU Ming-Shan;YANG Zuo-Min;SUN Qi-Xin;LIU Zhi-Yong

Acta Agron Sin. 2008, 34(03):  355-360.  doi:10.3724/SP.J.1006.2008.00355

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Yellow rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most devastating diseases in common wheat (Triticum aestivum L.) worldwide. Molecular markers are powerful tools in marker-assisted selection, gene pyramiding and gene cloning of important crop traits, especially for disease resistance. The objectives of this study were to develop tightly linked molecular marker of a yellow rust resistance gene against the prevalent Chinese races of Puccinia striiformis f. sp. tritici in an improved wheat line S2199 and to characterize its allelism with Yr5. Genetic analysis indicated that a single dominant gene was responsible for the yellow rust resistance in S2199, temporarily designated YrS2199. By screening 1 856 pairs of SSR primers, two markers—Xdp269 and Xgwm120 were found to be linked to the yellow rust resistance gene, with genetic distance of 0.7 and 11.0 cM, respectively. SSR marker Xgwm120 has been genetically and physically mapped on 2BL chromosome arm in wheat. By using Chinese Spring nullisomic-tetrasomics, ditelosomics and deletion lines of homoeologous group 2, Xdp269 was physically mapped on the terminal bin (0.89–1.00) of chromosome arm 2BL. Both allelism test of 700 F2 plants from the cross YrS2199/Yr5 and seedling tests of YrS2199 and Yr5 on 14 PST isolates indicated that YrS2199 and Yr5 are likely to be the same gene or allelic genes. The YrS2199 tightly linked SSR marker Xdp269 could be used as potential tool in cloning the yellow rust resistance gene or marker assisted breeding program.

Mapping QTLs of Resistance to Megacota cribraria (Fabricius) in Soybean

XING Guang-Nan, ZHOU Bin, ZHAO Tuan-Jie, YU De-Yue, XING Han, HEN Shou-Yi, GAI Jun-Yi

Acta Agronomica Sinica. 2008, 34(03):  361-368.  doi:10.3724/SP.J.1006.2008.00361

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Globular stink bug [Megacota cribraria (Fabricius)] is one of the important pests for soybean [Glycine max (L.) Merr.] in the central and southern China. However, very few reports on soybean resistant to M. cribraria were found in the literature. The objectives of the present study were to find QTLs associated with resistance to M. cribraria in soybean and to analyze the stability of mapped QTLs among years by using two RIL populations, NJRIKY (or KY) and NJRIWT (or WT) derived from the crosses of Kefeng 1 × Nannong 1138-2 and Wan 82-178 × Tongshanbopihuangdoujia, respectively. The 184 lines of KY and 142 lines of WT were tested and the percentage of black mildew on stem and purple spots on leaves was used as indicator to evaluate their resistance to M. cribraria under natural infestation during 2004–2006. There existed significant differences among lines in the two RIL populations during the three years, with heritability of 66.5%–88.8% in KY and 61.3%–84.8% in WT. The composite interval mapping (CIM) of the software Windows QTL Cartographer Version 2.5 was used to map QTLs. The linkage group D1a and C2 in KY and the linkage group H and D1b in WT were found to be related with resistance to L. indicata. The QTL qRMC-d1a-1 on Linkage group D1a was detected consistently associated with reaction to M. cribraria in KY during the three years, which accounted for 7.6%–31.4% of phenotypic variation; the QTL qRMC-c2-1 on linkage group C2 was detected in 2005–2006, which accounted for less phenotypic variation than the former one; the resistance alleles were from Nannong 1138-2. There appeared significant interactions between qRMC-d1a-1 and qRMC-h-1 in KY in 2005 and 2006. The QTL qRMC-h-1 on linkage group H was detected also consistently associated with reaction to M. cribraria in WT during the three years, which accounted for 16.3%–36.2% of phenotypic variation; the QTL qRMC-d1b-2 on linkage group D1b was detected in 2004-2005, which accounted for less phenotypic variation than the former one; the resistant alleles were from Tongshanbopihuangdoujia. Therefore, different QTLs conferred resistance to M. cribraria in KY and WT basically although the two QTLs in the latter population were also identified in one year in the former population. The fact that the QTLs were repeatedly detected in different environments indicated the resistance was controlled stably by the main QTLs. Based on the results, it is inferred that the markers linked to the detected QTLs should be useful for marker-assisted selection for resistance to M. cribraria in soybean.

Mapping and Analysis of QTLs on Maternal and Endosperm Genomes for Histidine and Arginine in Rice (Oryza sativa L.) across Environments

ZHENG Xi;WU Jian-Guo;LOU Xiang-Yang;XU Hai-Ming;SHI Chun-Hai

Acta Agron Sin. 2008, 34(03):  369-375.  doi:10.3724/SP.J.1006.2008.00369

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As a staple cereal crop in the world, rice feeds more than 50% of the world population. The improvement for rice quality including protein content and kinds of amino acid contents is an important work to meet the demands of a growing population. The genetic analysis on rice indicate that the inheritance of nutrient quality traits is complex, which involve the genetic effects from the triploid endosperm nuclear genes and the diploid maternal plant nuclear genes, being further partitioned into additive and dominance effects, and their genotype × environment (GE) interaction effects. So far, the magnitude and prevalence of interactions between quantitative trait loci (QTL) of the triploid endosperm genome or diploid maternal genome for rice traits are still largely unknown. Therefore, it is necessary to study the genetic main effects and GE interaction effects of the QTL from different genomes across environments. Investigations to identify QTL governing histidine (His) and arginine (Arg) contents of rice were conducted using the newly developed QTL mapping method including endosperm and maternal main effects and their GE interaction effects on quantitative traits of seed in cereal crops. Two backcross populations, which were a set of 241 RILs derived from an elite hybrid cross of ‘Shanyou 63’ crossed with ‘Zhenshan 97’ (BC1F1) or ‘Minghui 63’ (BC2F1), were used in two environments. The results showed that significant differences were found between the two parents for both quantitative quality traits. His and Arg of rice for Zhenshan 97 were higher than those for Minghui 63. The distributions of phenotypic values for His and Arg in BC1F1 (RILs × P1) and BC2F1 (RILs × P2) populations revealed normal distributions approximately. Both backcross populations also showed varying distributions in 1999 and 2000, implying that both amino acid traits were subjected to the modification by environments. A total of ten QTL associated with His content were mapped on chromosomes 1, 2, 3, 6, 7, 10, 11, and 12. Significant additive effects (ae and de) of QTL from diploid maternal plant and triploid endosperm were detected for all of these QTL. Two of them were also found to have visible endosperm dominance main effects and five QTL had significant environmental interaction effects. A total of eight QTL associated with Arg content of rice were mapped on chromosomes 2, 3, 5, 6, 7, 10, 11, and 12. Significant additive main effects of QTL from both genomes were all detected for all of these QTL. Two of them were also found to have visible endosperm dominance main effects and two QTL had significant environmental interaction effects. The proportions of phenotypic variation attributable to the total genetic main effects and GE interaction of QTL were 0.147 and 0.055 for His and 0.160 and 0.018 for Arg, respectively. These results showed that the control for His and Arg contents of rice was distributed over several chromosomes and the environmental interaction effects were also important for the performance of these quality traits.

Genetic Analysis of Lodging Resistance with Mixed Model of Major Gene Plus Polygene in Brassica napus L.

GU Hui;QI Cun-Kou;

Acta Agron Sin. 2008, 34(03):  376-381.  doi:10.3724/SP.J.1006.2008.00376

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Rapeseed is one of the most important oil crops in the world. Lodging damage results in not only lower seed yield and oil quality, but also easier infection to the infection of Sclerotinia and more difficulties for mechanized harvest. So it is of a great significance to study lodging resistance in B. napus L. However, lodging is a complex trait associated with several factors. It is difficult to evaluate in field. In this paper, inheritance of lodging resistance was analyzed applying the joint segregation analysis of a mixed genetic model of major gene plus polygene in six generations (P1, P2, F1, B1, B2, and F2 ) derived from two crosses of Zheping 1 (lodging resistance) × 04Pb11 (lodging) (Cross I) and Ning 1243 (lodging resistance) × 04Pb11 (Cross II) in B. napus L. Resistant pressure per plant (RPPP) was measured at flowering time by Digital Force Gauge, which was used to assess the ability of lodging resistance, and the correlation between RPPP and lodging scale was scored at mature time (r = -0.38, P≤0.01). The results showed that lodging resistance was dominated by two major genes with additive-dominance-epistatic effects plus polygenes with additive-dominance-epistatic effects (E-0 model) in Cross I, and two major genes with additive-dominance-epistatic effects plus polygenes with additive-dominance effects (E-1 model) in Cross II. The additive effects of two major genes in two crosses were more powerful than the dominant one (︱h/d︱＜1). On average, Hereditability of major genes (hmg2) was 54.71% in F2 population, and that of polygenes (hpg2) only detected in B1 population was 10.56%. It indicated that the lodging resistance in B. napus L. was dominated by major genes. In addition, the environmental variance and the genetic variance accounted for 46.57% and 53.43% of the phenotypic variance in each population respectively, indicating that the environmental factors have a great effect on lodging in B. napus L.. However, higher hereditability of major genes can be favorable to an efficient selection in early generation of lodging resistance breeding.

Deducing Maturity Genotype of the Chinese Soybean

NING Hui-Xia;LI Ying-Hui;LIU Zhang-Xiong;CHANG Ru-Zhen;GUAN Rong-Xia;LUO Shu-Ping;QIU Li-Juan

Acta Agron Sin. 2008, 34(03):  382-387.  doi:10.3724/SP.J.1006.2008.00382

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In order to find the tightly linked diagnostic SSR (simple sequence repeat) marker on soybean LG related to the maturity genotype and further deduce the maturity genotype of Chinese varieties, 215 pairs of SSR marker were selected to analyze 23 soybean germplasms in China and 35 introduced maturity Near-Isogenic Lines from U.S.A. Among them, 125 SSR markers were polymorphic and 8 SSR markers were relative to the maturity genotype. In detail, on the Clark background, Satt229 tightly linked to E3/e3 maturity locus, five markers including Sct_010, Satt294, Satt247, Satt452, and Satt156 tightly linked to E4/e4 maturity locus; both on the Clark and Harosoy background, Satt071and Satt178 tightly linked to E7/e7 maturity locus. Anyway, considered the NILs in the Harosoy background, only two markers (Satt071and Satt178) could be used to deduce the genotype of soybean germplasms in China. Then the maturity genotype of 25 varieties from China was deduced. UPGMA clustering tree was constructed based on the molecular data of 8 SSR markers correlated to maturity gene, and there were four groups were clustered. The result showed that the materials with the same genetic background were clustered together. The materials with the Clark background were clearly different from those with the Harosoy background.

Mapping QTL for 3 Panicle Exsertion-related Traits in Rice (Oryza sativa L.) under Different Growing Environments

QIAO Bao-Jian;ZHU Xiao-Biao;WANG Ying-Ying;HONG De-Lin

Acta Agron Sin. 2008, 34(03):  389-396.  doi:10.3724/SP.J.1006.2008.00389

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Panicle exclosure in CMS line is highly correlated with outcrossing rate of CMS in hybrid rice seed production. Panicle enclosure is occurred when flag leaf sheath length exceeds the uppermost internode length. In order to improve panicle exertion, it is necessary to understand the genetic mechanism of flag leaf sheath length, the uppermost internode length, and panicle enclosure. Under 3 different growing environments, the experiment was conducted using 98 backcross inbred lines (BILs) derived from a backcross of Nipponbare (japonica) / Kasalath (indica) // Nipponbare by the single seed descent methods. At 5% of genome-wide type I error, we detected QTLs of the 3 traits by composite interval mapping method. The results showed that 3 QTLs for flag leaf sheath length were detected totally, which were located on chromosome 1, 3, 4, and explained 12.83%–18.5% of observed phenotypic variance. The qFLL-1 was detected in 3 environments, its positive allele was from Nipponbare, qFLL-3, qFLL-4 were detected in single environment, their positive alleles were from Kasalath. For the uppermost internode length, 3 QTLs were detected on chromosome 1, 3, 6, and explained 5.64%–14.18% of observed phenotypic variance. The qUIL-6 was detected in all 3 environments, its positive allele from Nipponbare. The other 2 QTLs were detected in 2 of the environments, and Kasalath carried positive allele. Four QTLs for panicle enclosure length were detected on chromosome 1, 3, 5, 10, explained 6.8%–17.76% of observed phenotypic variance. The qPEL-10 was detected in all 3 environments. qPEL-5 was detected in 2 of the environments. Positive alleles of qPEL-10 and qPEL-5 were from Nipponbare. The other 2 QTLs were detected only in single environment, and their positive allele came from Kasalath.

Cold Tolerance of Transgenic Tobacco Carrying Gene Encoding Insect Antifreeze Protein

WANG Yan;QIU Li-Ming;XIE Wen-Juan;HUANG Wei;YE Feng;ZHANG Fu-Chun;MA Ji

Acta Agron Sin. 2008, 34(03):  397-402.  doi:10.3724/SP.J.1006.2008.00397

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Most of crops are susceptible to cold and frost. When temperature decreases to -1℃, ice makes plant cells desiccated and cellular membrane shrinked. Expression of insect antifreeze protein genes with very high thermal hysterisis activity in plants is a possible way for increasing the cold tolerance of cold-sensitive plants. The MPAFP149 gene from Xinjiang desert insect Microdera punctipennis dzhunarica was constructed to the plant expression vector pCAMBIA1302 by sub-cloning, and then the recombined vector pCAMBIA1302-MPAFP149 was transformed into Agrobacterium tumefacines EHA105. Transgenic tobacco was obtained via leaf-disc method by Agrobacterium-mediated transformation. PCR and PCR-Southern analysis showed that the MPAFP149 gene was successfully integrated into the tobacco genome. The result of RT-PCR also verified that MPAFP149 gene was transcripted at mRNA level. The relative conductivity of T0 generation of transgenic tobacco at －1℃ for 48 h was 28.83%, significantly lower than that of wild tobacco which was 82.91%. Meanwhile, the phenotype of transgenic tobacco was superior to that of wild tobacco, suggesting that transgenic tobacco had better cold tolerance than wild tobacco. Recovering experiment at the room temperature indicated that transgenic tobacco was able to recover from cold stress and regenerate. The results proved that transgenic tobacco carrying MPAFP149 gene was more cold tolerant than wild tobacco, which provided a theoretical and applied foundation for relieving cold damage to cold-sensitive crops in spring.

Genetic Diversity and Populati

MA Dian-Rong;LI Mao-Bai;WANG Nan;XU Zheng-Jin;CHEN Wen-Fu

Acta Agron Sin. 2008, 34(03):  403-411.  doi:10.3724/SP.J.1006.2008.00403

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Weedy rice refers to rice plants growing in paddy field and its surrounding area as a weedy type, which is distributed in rice-transplanting areas in Liaoning Province of north China. Field surveys were conducted to define the distribution region of Chinese weedy rice, weedy rice resources were collected from the main rice-growing regions of Liaoning Province in the autumns 2003–2005, and the phenotypic diversity of weedy rice was tested at the Rice Research Institute of Shenyang Agricultural University in 2006. Weedy rice seeds were sown on 12 April and seedlings were transplanted to the field on 20 May 2006. Data were collected on various morphological variables of weedy rice. Samples of weedy rice were analysed with 30 SSR makers and compared with the collections of cultivated rice and wild rice O. rufipongon. The percentage of polymorphic loci was 86.67% and Shannon's information index was 0.762, showing that the genetic diversity of Liaoning weedy rice is very high. The GST of 0.843 suggested that the main genetic variation of weedy rice resided among populations. Weedy rice populations in Liaoning were closely related to cultivated japonica rice but distantly related to O. rufipongon and cultivated indica rice. Weedy rice in Liaoning most probably originated from the local cultivated japonica rice through natural hybridization and natural mutation. The weakness of breeding and cultivation methods promoted the producing of Liaoning weedy rice.

Efficiency of Spatial Statistical Analysis in Superior Genotype Selection of Plant Breeding

HU Xi-Yuan;LI Jian-Ping;SONG Xi-Fang

Acta Agron Sin. 2008, 34(03):  412-417.  doi:10.3724/SP.J.1006.2008.00412

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The objective of this study was to evaluate the efficiency of spatial statistical analysis in the superior genotype selection of plant breeding using the data from a yield trial of wheat with 56 test lines in a block design. The spatial analysis used linear mixed model with spatial covariance for residuals which was estimated using semivariogram defined in geostatistics. Results showed a typical spatial correlation of residuals, which allowed a reduction in standard errors of line effect estimate and a greater efficiency of F- and t-test in discrimination of lines when spatial analysis was applied. Furthermore, in estimation of line effect the spatial analysis was less influenced by assay condition variation, and led to a different ranking and selection of genetic materials, in comparison with traditional analysis of variance.

Expressions of Three Members of ACS Gene Family Induced by Ethephon Relationship of Ethylene Production and Sugar Accumulation in Sugarcane Stems

WANG Ai-Qin;;FAN Ye-Geng;ZHAO Xiao-Yan;HE Long-Fei;YANG Li-Tao;LI Yang-Rui;

Acta Agron Sin. 2008, 34(03):  418-422.  doi:10.3724/SP.J.1006.2008.00418

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1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is one of the key rate-limiting enzymes for ethylene biosynthesis in higher plant. In order to study expressions of ACS genes in stalks regulated with ethephon and its correlation with ethylene production and sucrose accumulation in sugarcane, the spatial and temporal expressions of the three genes were tested in the stalks of sugarcane with Sc-ACS1, Sc-ACS2, and Sc-ACS3 as the probes, respectively, based on the cloning of Sc-ACS1, Sc-ACS2 and Sc-ACS3 of ACS gene family. Northern blotting analysis showed that three members of ACS gene family kept expressions during late growth stage in the varieties and internodes with a lower level except of Sc-ACS3. Ethephon treatment increased expressions of the three genes in the immature and maturing internodes. Sc-ACS1 and Sc-ACS2 maintained the highest expression level for 30 d and returned to normal level later, however, Sc-ACS3 kept the highest level for 45 d in the immature stalks. The ethephon-induced gene expressions were in accordance with the significant effects on ethylene production and sucrose accumulation in the immature and maturing internodes. The ethylene production was correlated negatively with the sucrose accumulation in internodes of variety GT17 significantly at P≤0.01 and P≤0.05 at 14 d and 28 d after treatment with ethephon, respectively, but not significantly in the variety B1.

Transformation, Inducing and High-Frequency Regeneration of Embryogenic Callus Initiated from Mature Embryos of Maize (Zea mays L.)

WANG Shi-Yu;ZHENG Yong-Lian;LIU Ya;ZHAO Jiu-Ran;ZHANG Fang-Dong

Acta Agron Sin. 2008, 34(03):  423-428.  doi:10.3724/SP.J.1006.2008.00423

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Immature embryo-derived callus is more efficient for transgenic and plant regeneration than calli from other explant tissues. It’s reported that embryogenic callus can be initiated from mature embryos. The use of mature embryos from dry seed are easy to handle, available year round and in bulk quantities. In this study we established an efficient transgenic acceptor system and developed some new methods on maize (Zea mays L.) tissue culture, plant regeneration and genetic transformation with embryogenic callus initiated from mature embryos of three elite inbred lines CML295, CML304, and 18-599R. The calli were cultured in subculture medium of immature embryos. Tissue slice showed that the structure of callus formed from mature embryos was the same as those from immature embryos, being the typeⅡ embryogenic callus. The calli were transferred into regeneration medium of immature embryos supplemented with 2 mg L-1 6-BA. The regeneration frequencies of the calli from mature embryos of CML295, CML304, and 18-599R were 68.6%, 75.4%, and 84.8%, respectively. Vector pCAMBIA1301 was transformed into callus from mature embryos of CML295, CML304, and 18-599R by particle gun using GUS as a report gene; vector pCAMBIA1303 was transformed by particle gun using GFP as a report gene, with GUS staining frequency of 57.9%, 62.5%, and 73.1%; and GFP transient expression frequency of 23.3%, 40%, and 45.5%, respectively. The transgenic rates of embryogenic callus from mature embryos of the three inbred lines were similar to those from immature embryos. In conclusion, using embryogenic callus from mature embryos as transgenic acceptors is efficient and available.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Root Morphological and Physiological Characteristics in Rice Genotypes with Different N Use Efficiencies

WEI Hai-Yan;ZHANG Hong-Cheng;;ZHANG Sheng-Fei;HANG Jie;DAI Qi-Gen;HUO Zhong-Yang;XU Ke;MA Qun;ZHANG Qing;LIU Yan-Yang


Acta Agron Sin. 2008, 34(03):  429-436.  doi:10.3724/SP.J.1006.2008.00429

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Nitrogen is the most important input required in rice production although over use of N causes so many environment problems. It is well known that N use efficiency is varied in different rice genotypes. Therefore, it is important to explore and exploit the potential contributing to the N use efficiency. As an integral part of plant organs, rice root plays an important role in absorption and utilization of N from soil and fertilizer. In this research, a field experiment with 225 kg ha-1 N fertilizer application was carried out in 2006 on the farm of Yangzhou University, Jiangsu province, China. A total of 12 rice genotypes ( 6 N-efficient and 6 N-inefficient ) selected from 120 rice cultivars grown in Yangzhou during 2004 and 2005 were adopted to investigate the charac-teristics of root morphology and physiology in rice types with different N use efficiencies. Relationship between N use efficiency and indexes of root morphology and physiology was also analyzed. The results showed that at different growth stages, the indexes of root morphology and physiology including the root dry weight, root volume, total absorbing surface area of root, active absorbing surface area of root, ratio of active absorbing surface area to total absorbing surface area in N efficient rice type were obviously higher than those in N inefficient rice type. At the critical stage of productive tillering and the stage of elongating, the ratio of root to shoot in N efficient rice type was significantly higher than that in N inefficient rice type while the trend was con-trary at the stages of heading and maturing. Before the stage of maturing, the root oxidation ability of α-NA in N efficient rice type was superior to that in N inefficiency rice type while at the stage of maturing the root oxidation ability of α-NA in N efficient hybrid rice was appreciably lower than that in some N efficient rice cultivars. N use efficiency positively correlated to all the above morphological and physiological indices at all growth stages, with the exception of negatively correlation to the ratio of root to shoot at the stage of heading and maturing. It could be concluded that the root morphology is good and the root is vigorous in N efficient rice type, its morphological and physiological characteristics ensures the efficient absorption and utilization of N in all its life, and proper ratio of root to shoot and the harmonious growth of root and shoot can also improve the efficiency of N absorption and utilization.

Activity Changes for Enzymes Associated with Fiber Development and Relation with Fiber Specific Strength in Two Cotton Cultivars

SHU Hong-Mei;WANG You-Hua;ZHANG Wen-Jing;ZHOU Zhi-Guo

Acta Agron Sin. 2008, 34(03):  437-446.  doi:10.3724/SP.J.1006.2008.00437

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Fiber strength is one of the important criterions of cotton quality, and many complex physiological and biochemical processes are involved in fiber formation. To detect the relationship enzyme activities in cotton fiber development with fiber specific strength, two cotton cultivars (Kemian 1 which is a cultivar with high strength fiber, average fiber specific strength is 35 cN·tex-1; Dexiamian 1 which is a cultivar with low strength fiber, average fiber specific strength is 26 cN·tex-1.) were used to investigate the characteristics of sucrose synthase (SuSy) and β-1,3-glucanase which play very important roles in developing cotton fiber, and dynamic changes of the related gene (sucrose synthase, β-1,3-glucanase, β-1,4-glucanase, Expansin) expression. The results showed that there were differences between the two cultivars in variations of the cellulose deposition and fiber specific strength which was related with the changes of key enzyme activities and the gene expression levels. The activity and gene expression of sucrose synthase and β-1,3-glucanase were higher in Kemian 1 than in Dexiamian 1. High concentration and high gene expression of SuSy and β-1,3-glucanase in cotton fiber resulted in a long period and tempered cellulose accumulation and high strength fiber formation. Dexiamian 1 had low activities of the key enzymes and low expression levels which led to a short and rapid cellulose accumulation duration and low strength fiber. From results above, we suggest that the different characteristics of key enzymes activity (sucrose synthase and β-1,3-glucanase ) in fiber of different cotton cultivars may cause the differences in the cellulose accumulation and fiber strength.

Canopy Structure and Photosynthesis Traits of Summer Maize under Different Planting Densities

LÜ Li-Hua;TAO Hong-Bin;XIA Lai-Kun; HANG Ya-Jie;ZHAO Ming;ZHAO Jiu-Ran;WANG Pu;

Acta Agron Sin. 2008, 34(03):  447-455.  doi:10.3724/SP.J.1006.2008.00447

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Canopy structure has strong effects on photosynthesis and grain yield in maize (Zea mays L.). Planting density is one of the most important factors that can regulate canopy structure. Many researches have shown that leaf area index (LAI) and leaf area duration (LAD) increase accordantly with the proper increase of planting density, but the percent transmission decreases sharply under excessive high density, resulting in uneven light distribution within canopy and photosynthesis reduction. We need to know which proper planting densities for cultivars lead to little influence on photosynthesis and higher grain yield in summer maize. However, so far few reports on this topic have been found and no quantitative criteria can be used in evaluating canopy structure of different maize cultivars. Therefore, we conducted an experiment with three cultivars and three planting densities in the field having medium soil fertility and application of 180 kg N ha^-1 in Wuqiao Experimental Station (37°41′02″N，116°37′23″E) of China Agricultural University in 2006 to establish such quantitative criteria for high yielding cultivars in North China Plain. The split plot design was employed with main plot of plant density (low, medium, and high respectively), sub-plot of cultivar (CF008, Zhengdan 958, and Jinhai 5 respectively), and three replicates in each sup-plot. According to plant type, the densities of three cultivars were 9.75×104 (low), 11.25×104 (medium), and 12.45×104 (high) plants ha-1 for CF008; 8.25×104 (low), 9.75×104 (medium), and 11.25×104 (high) plants ha-1 for Zhengdan 958; and 6.75×104 (low), 8.25×104 (medium), and 9.75×104 (high) plants ha-1 for Jinhai 5. The high-yielding canopy structure and photosynthesis were obtained under both low and medium densities of the three cultivars. Percent transmission, leaf angle, and stem diameter decreased with the increase of plant density. The chlorophyll relative content (SPAD) and the rate of net photosynthesis rate (Pn) were the smallest under high density because of the uneven light distribution within canopy. For CF008, SPAD value of ear leaf and the third leaf under ear decreased sharply in later growth stages. LAD and LAI values before mid-filling stage were greater under medium or high densities, while different tendency occurred in the maturity stages. Moreover, the proportion of after-silking LAD was greater under low or medium densities, showing that canopy structure was unsuitable under high density due to early senescence. For Zhengdan 958 and Jinhai 5, LAD after silking was greater than that before silking, which was benefit for high grain yield. Our results confirmed that proper planting density can establish high-yielding canopy structure and improve population photosynthesis and yield in maize. We also obtained a series quantitative criteria for high-yielding canopy structure based on the data from Wuqiao area: percent transmission of 13.4%–19.45% in silking stage and 16.19%–21.48% in mid-filling stage under low or medium densities; LAI of 5.59–6.75 in silking stage and 2.24–3.68 in maturity stage, especially highen in middle and upper leaf layers in maturity stage under low or medium densities; Pn of 33.6–43.8 μmol CO2 m-2 s-1 in middle and upper layer leaves in silking stage under low or medium densities; higher LAD after silking under low or medium densities, with 172.01–235.91 m2 d m-2 under medium density.

Effects of Irrigation Regimes during Grain Filling on Grain Quality and the Concentration and Distribution of Cadmium in Different Organs of Rice

HUANG Dong-Fen;XI Ling-Lin;WANG Zhi-Qin;LIU Li-Jun;YANG Jian-Chang

Acta Agron Sin. 2008, 34(03):  456-464.  doi:10.3724/SP.J.1006.2008.00456

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The objective of this study was to investigate whether the grain quality could be improved and the proportion of cadmium (Cd) be reduced in grains through a proper irrigation regime when rice was planted in Cd-contaminated soil. Two rice cultivars of Yangjing 9538 (japonica) and Yangdao 6 (indica) were pot-grown. 150 mg kg-1 Cd was added into pots before seedling transplanting (Cd treatment), and no Cd addition was taken as control (CK). Three irrigation regimes, well-watered (WW), moderate dry-wet alternate irrigation (MD, soil was re-watered when soil water potential reached at –20 kPa), and severe dry-wet alternate irrigation (SD, soil was re-watered when soil water potential reached at –40 kPa), were imposed from 7 d after heading to maturity. The results showed that under the same Cd concentration in soil and when compared to WW, MD significantly increased, whereas SD significantly reduced, seed-setting rate, 1 000-grain weight, grain yield, brown rice rate, milled rice rate, and head rice rate. MD markedly reduced, while SD increased, chalkiness. There were no significant differences in the seed-setting rate, 1000-grain weight, and each index of rice quality between the Cd treatment and the control. Under the Cd treatment and compared to WW, MD and SD significantly increased the concentration and proportion of Cd in roots, while significantly reduced Cd concentration in stems and leaves and reduced Cd proportion in grains. Cd concentrations in grains and milled rice were significantly higher under SD than under WW, and exhibited no significant difference between MD and WW. SD showed lower proportion of Cd in milled rice, when compared to MD or WW. The two cultivars behaved the same. The results indicate that a moderate dry-wet alternate irrigation during grain filling could increase grain yield, improve milling and appearance quality and not increase Cd concentration or even reduce Cd proportion in grains. Reasons for variations in grain yield, quality, and the concentration and proportion of Cd under different irrigation regimes were analyzed from the aspects of root activity, photosynthetic characters, and Cd translocation.

Starch Granule Size Distribution in Grains of Strong and Weak Gluten Wheat Cultivars

DAI Zhong-Min;WANG Zhen-Lin;ZHANG Min;LI Wen-Yang;YAN Su-Hui;CAI Rui-Guo;YIN Yan-Ping;

Acta Agron Sin. 2008, 34(03):  465-470.  doi:10.3724/SP.J.1006.2008.00465

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Granule size and structure of starch affects starch quality fatally in wheat (Triticum aestivum L.). The quantity and volume of starch granule and starch components in grain vary in different types of wheat. Many researches have unveiled the distribution of starch granule size in wheat grain, but rarely mentioned the relationship between grain quality and starch granule characteristics. In the present experiment, the purpose was focused on starch granule size distribution and the relationship between starch granule size and grain quality properties. Four winter wheat cultivars (Defeng 3 and De 99-3 as strong gluten type, Binyu 535 and Lumai 21 as weak gluten type) were planted at Tai’an and Dezhou experimental sites in Shandong Province, respectively, with randomized block design in 2004–2005 growing season. The starch granule in matured grain was 0.37–52.60 μm in diameter, containing smaller B-type (diameter <9.8 μm) and larger A-type (diameter >9.8 μm) granules. The distribution frequency showed typical two-peak curve in starch granule volume and surface area, and single peak curve in number of starch granule. The number of B-type granule accounted for over 99% of the total starch granule. The percentages of volume and surface area of B-type starch granules were higher than those of A-type granule in the strong gluten wheat cultivars, but on the contrary in the weak gluten cultivars. The contents of amylose and starch were negatively correlated with the volume of 2.0–9.8 μm (r = －0.483*, －0.679**) and <9.8 μm (r = －0.465*, －0.667**) starch granules, respectively, but positively correlated to 9.8–18.8 μm starch granule (r = 0.648**, 0.673**). The content of protein was positively correlated with the volume of 2.0–9.8 μm (r = 0.528**) and <9.8 μm (r = 0.514*) starch granules, respectively, but negatively correlated with that of 9.8–18.8 μm (r = －0.548**) starch granule. The contents of starch and protein had no correlation with volume percentage of starch granule with other size ranges.

Factors Associated with Root Border Cell Development in Peanut

ZHANG Yu-Chen;MA Bo-Jun;GU Zhi-Min;SHI Mei-Feng

Acta Agron Sin. 2008, 34(03):  471-476.  doi:10.3724/SP.J.1006.2008.00471

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Border cells (BCs), originated from root-cap meristem, are a kind of active cells deposited in the periphery of roots to protect the root tips from extracellular biotic and abiotic stresses. Some investigators believe it is a constitutive expression in BC’s production, while others suggest that it is an induced process regulated by intro- and extro-signals. BCs in different plant species show completely different responses to temperature stress. In this paper, we investigated the factors associated with the production and development of BCs in peanut (Arachis hypogaea L.), which had never been reported before. Two peanut cultivars, Xinchang Xiaojingsheng and Jiangxi Yibazhua were employed and their seeds were aerobic cultured after imbibition. The BC number and activity (percentage of BC survival/total) as well as their responses to pectin methylesterase (PME) activity, BC liquor, temperature, and osmotic potential were measured. Under normal cultural condition, the number of BCs increased with the development and elongation of the root. The first BC formation almost synchronously occurred with root tip emergence. When the root length was 13–17 mm at 25℃, the number of BCs reached the maximum (about 10 000 BCs). When the BCs were removed from root tip, a new generation of BCs was induced within 72 h. During this period, the PME activity increased quickly to the maximum within 4 h and then decreased to pre-induction background levels subsequently, suggesting that the PME may play an important role in production and development of BC. The number and survival percentage of detached BCs were significantly different when the roots cultured in the media with three different BC liquor concentrations containing extracellular inhibitor of BC. The extracellular inhibitor of BC released could inhibit not only the production of BC but also its activity, and the inhibition was strong with the increment of the concentration. The extracellular inhibitor affected more greatly on BC production as compared with the BC activity. Temperature directly or indirectly affected the root growth, and regulated the production and development of BCs. Both high and low temperatures inhibited the root growth and affected the production rate, maximum number, and activity of BC, and low temperature had more severe harmness to the development of the peanut root. Temperature had greater impact on BC activity as compared with secretion rate of BC. The activities of detached BCs in different culture conditions show significant difference. The survival percentage of detached border cells was significantly higher under culture in the aerobic or mannitol than in MS medium or ddH2O, suggesting that maintenance of mucus layer osmolarity in root apex can maintained the survival percentage of BCs at a high level within a relative long time. The results supported the hypothesis of induced model of BC formation that regulated by the intrinsic and extrinsic signals.

Importance of Identification of Waterlogging Tolerance at Early Growing Stages of Peanut in Laboratory to Field Screening

LI Lin;LIU Deng-Wang;ZOU Dong-Sheng;;XIAO Lang-Tao;WANG Ruo-Zhong;LIU Fei;ZHAO Wei;QIN Guo-Dong;ZHU Xu-Dong

Acta Agron Sin. 2008, 34(03):  477-485.  doi:10.3724/SP.J.1006.2008.00477

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Waterlogging is one of the main limiting factors in worldwide peanut production. It is useful to develop a prompt approach for waterlogging tolerance screening at early growth stages. To study difference of waterlogging tolerance among peanut varieties and in the early growth stages and the correlation with waterlogging tolerance based on yield in the field, seeds of 8 varieties were planted in shallow and deep water for 180 h, seedlings were waterlogged with sand soil in laboratory for 10 days and in field for 10 d (short-term) and 88 d (long-term), then the germination ratio, seedlings growth and development indexes, alcohol dehydrogenase activity (ADH), field yields under waterlogging (WY10, WY88) and waterlogging tolerance coefficients(WTC10, WTC88）were measured. The results were as follows: (1) Peanut was sensitive to waterlogging, and the tolerance varied with waterlogging degree, varieties and imposing time. Seeds of each variety germinated in shallow water, while not in deep water. At seedling stage, roots were more severely reduced by waterlogging stress than above-ground parts of plant (AGPP), difference of waterlogging tolerance among varieties could be judged phenotypically by color and weight of roots. (2) Alcohol dehydrogenase (ADH) activity in peanut roots increased significantly under waterlogging condition (hypoxia induction). The plants of varieties with higher ADH activity after 10 d waterlogging were generally runt. (3) All waterlogging tolerance indexes based on yield were correlated with ADH activity and roots color negatively, and with weight of roots positively per plant, weights of AGPP and total plant positively, especially weight of roots were significantly and positively correlated with WY10. (4) The time for peanut waterlogging tolerance screening in shallow and deep water should be 180 and 120 h respectively at germinating stage, and 3–10 d at seedling stage. It can be concluded that indoor identification of waterlogging tolerance in laboratory at early stages is an important reference for on-farm test.

Effects of Different Irrigation Regimes on Some Physiology Characteristics and Grain Yield in Paddy Rice during Grain Filling

ZHANG Rong-Ping;MA Jun ;;WANG He-Zheng;LI Yan;LI Xu-Yi;WANG Ren-Quan

Acta Agron Sin. 2008, 34(03):  486-495.  doi:10.3724/SP.J.1006.2008.00486

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Draught and irrigation regime

have been attracted more and more attention because of limited water resources in China.Rice is one of the main stable food crops in the world, and may suffer serious water stress during its growth period. Grain yield under different irrigation regimes during grain filling, and its physiological mechanism are unclear. So the experiments were carried out using three hybrid rice of Gangyou 527, D you 363, and Shanyou 63 in potted and farmland experiments to investigate the effects of four irrigation regimes [dry cultivation (DC), damp irrigation (DI), the treatment C that controlled damp irrigation before booting stage, shallow irrigation at booting stage, wetting-drying alternation irrigation from heading stage to mature stage, and submerged irrigation (SI)] on photosynthetic rate, osmotic regulators, antioxidant enzyme activities, and grain yield. The results indicated that the treatment C and DI had high chlorophyll content in flag leaf, with slow senescence of flag leaf and high photosynthetic rate (P_n) of flag leaf. Both the treatment C and DI promoted the accumulation of soluble sugar content, amino acids content, and proline content, etc., and enhanced the catalase (CAT) and peroxidase (POD) activities, which maintains the natural metabolism of cells. However, compared with submerged irrigation, changes of these substances were sensitive to water stress of DC. It was showed that grain yield of the treatment C was the highest. Grain yield and its components were significantly higher under DI than under SI, but the potential of enhancing grain yield was slightly weaker under DI than under the treatment C. Decreases of grain yield and its components were obviously less than those of the treatment C. These results suggested that photosynthetic rate, osmotic regulators content antioxidant enzyme activities, and grain yield are correlated significantly to drought resistance of rice cultivars.

Anatomic Analysis on Heterosis in Three Transgenic Bt Pest-Resistant Hybrid Cotton (G. hirsutum L.)

ZENG Bin;WANG Qing-Ya;TANG Can-Ming;

Acta Agron Sin. 2008, 34(03):  496-505.  doi:10.3724/SP.J.1006.2008.00496

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The anatomical characterization is the basis of physiological function of plants, so it is necessary to analyze heterosis performance and to reveal anatomical mechanism of heterosis. Anatomical characterization of the functional leaf in stem and vascular bundles of sympodial leaf stalk and boll stalk during flowering stage was investigated using three transgenic Bt pest-resistant cotton hybrids Nankang 3, Lumianyan 15, Xiangzamian 3, and their parents. The result showed that there were significant differences between hybrid and its parents in distribution of vascular bundles in the leaf nervures of the functional leaf (the fourth from top) in main stem. Three types of vascular bundles, three-offshoot, two-offshoot and no-offshoot were observed in leaf nervures of all tested materials. These were three-offshoot type in 3 hybrids and one of their parents, implying that the three-offshoot type was inherited dominantly. There were differences in the number of vessels, area of a vessel, area of all vascular bundles, area ratio of vascular to transection, leaf thickness, palisade tissue length, and palisade tissue width with different parents and hybrids. The total area of vascular bundles of functional leaf nervures in three hybrids were 0.72–0.77. The ratio of palisade tissue to spongy tissue of all hybrids was 1.12–1.15, suggesting that there existed transgressive or mid-parent heterosis in all hybrids. The total area of stomata per unit leaf area was a useful index for characteristic of stoma. There were transgressive heterosis in total area of stomata per unit leaf area on down leaf surface for three hybrids, but no heterosis on upper surface. There were negative correlation between two sides of leaf in the total area of stomata per unit leaf area (mm² cm-²) of three hybrids, and significant negative correlation between stoma frequency and stama length (R²=0.5087), and positive correlation between stoma frequency and total area of stomata per unit leaf area (R²=0.5943) for upper surface of leaf but not significant for down surface of leaf. Moreover, there was significant positive correlation between leaf stalk of fruit branch and boll stalk in the number of vessel and area of a vessel, it demonstrated that the leaves on fruit branch have more contribution to the boll development than functional leaves in stem (R₁²=0.4791*, R₂²=0.4702*).

Selenium Content in Seedling and Selenium Forms in Rhizospheric Soil of Nicotiana tabacum L.

QIN En-Hua;YANG Lan-Fang;

Acta Agron Sin. 2008, 34(03):  506-512.  doi:10.3724/SP.J.1006.2008.00506

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Selenium (Se) is an essential trace element for human and animals, and it may be beneficial to increase Se content of tobacco (Nicotiana tabacum L.), but the relationship between Se availability and forms in soil for plant growth had been rarely reported so far. In order to understand the relationship between the Se content in tobacco and soil, and to develop Se-enriched tobacco, we performed a pot experiment using cultivar NC89 with natural Se-enriched and Se-supplied soil treatments. The Se content in seedlings and the Se forms in rhizospheric and nonrhizospheric soil were analyzed. The results showed that selenium content was higher in roots than in shoots of tobacco at seedling stage; it increased both in roots and shoots of tobacco with increase of Se level in natural Se-enriched soil, and there was a significant correlation between Se content and soil Se applications. In natural Se-enriched soil, the residual Se (Res-Se) content was the highest which accounted for more than 2/3 of the total Se in middle and high Se-enriched soil, while in Se-supplied soil, the content of extractable Se with KH₂PO₄ (KH₂PO₄-Se) was the highest which accounted for 43%–46% of total Se and was significantly correlated to Se content in tobacco. Both in natural Se-enriched and Se-supplied soil, content of extractable selenium with K₂SO₄ (K₂SO₄-Se) was the least which was less than 1% of total selenium, but the contents of total selenium, KH2PO4-Se and NH₃·H₂O-Se were significantly higher in rhizospheric soil than in nonrhizospheric soil. In Se-supplied soil, the percentage of NH₃·H₂O-Se was higher and the percentage of Res-Se was lower in rhizosphere than in nonrhizosphere. Our experiment showed that tobacco could accumulate Se well from soil, and absorb Se easier from Se-supplied soil than natural Se-enriched soil. The rhizosphere of tobacco, where distributed more available Se, can promote the formation of NH₃·H₂O-Se and reduce the Se fixation with minerals in soil, therefore increase Se availability in soil.

Effect of Nitrogen Applied before Transplanting on Tillering and Nitrogen Utilization in Rice

ZHENG Yong-Mei;DING Yan-Feng;WANG Qiang-Sheng;LI Gang-Hua;WANG Hui-Zhi;WANG Shao-Hua

Acta Agron Sin. 2008, 34(03):  513-519.  doi:10.3724/SP.J.1006.2008.00513

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Nitrogen (N) before transplanting, applied in seedling-bed and carried to the paddy field with seedlings is proposed in this paper. The effect of this method on tillering, N accumulation, N fertilizer utilization efficiency (NUE), and grain yield were investigated in a field experiment with a japonica cultivar Ningjing 2. The results indicated that, on the condition of equal basic and tillering N fertilizer, the tillers number in the treatment of nitrogen fertilizer applied before transplanting (N-100%) was 300 thousand ha-1 higher than that in treatment of no N fertilizer applied before transplanting (CK). At the critical stage of productive tiller, the tillers rate with leaf age >3 in N-100% treatment was remarkably higher than that in CK. Compared with CK, the rate of effective tillers, number of effective panicles, N accumulation, NUE, and grain yield of N-100% treatment were markedly increased. But the application of N was only 5.55 kg ha-1 more than that of CK. In N-75% treatment the application of N was 32.4 kg ha-1 lower than that in CK, while N accumulation and NUE were higher than those in CK. Compared with CK, N application of N-50% treatment was too lower, therefore it had negative effect on accelerating tiller’s development. As a result NUE and grain yield of N-50% treatment were observably lower than that of CK. The results suggested that proper N fertilizer applied before transplanting had positive effect on accelerating tiller’s development, and enhancing rate of effective tillers. Moreover, application of N fertilizer before transplanting could reduce the quantity of basic and tillering N fertilizer, speed absorption and utilization of N fertilizer, and increase N accumulation and NUE in rice.

RESEARCH NOTES

Isolation and Preliminarily Functional Analysis of SGT1 Gene of Thinopyrum intermedium

WANG Kai;DU Li-Pu;ZHANG Zeng-Yan;LIAO Yong;XU Hui-Jun;YAO Wu-Lan;HUANG Huang;YANG Kun;XIN Zhi-Yong

Acta Agron Sin. 2008, 34(03):  520-525.  doi:10.3724/SP.J.1006.2008.00520

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To understand the role of SGT1 gene in wheat (Triticum aestivum L.) diseases resistance, we used RT-PCR and RACE methods to isolate SGT1 genes from Thinopyrum intermedium. The SGT1 was named TiSGT1. The deduced TiSGT1 protein possesses the typical domains of known SGT1 proteins and shows highly homology with barley SGT1 protein. A highly efficiency expression vector of TiSGT1 was constructed by genetic recombination, and transformed into the wheat cultivar ‘Yangmai 12’ by biolistic particle method. Transformation plants were analyzed by PCR, Southern hybridization, and RT-PCR methods. The results showed that the TiSGT1 gene could be inherited from T0 to T2 generations, and could be expressed. The results of disease resistance test indicated that the over-expression of SGT1 in the transgenic wheat enhanced resistance to barley yellow dwarf virus and powdery mildew, and TiSGT1 could be used as a potential gene resource for improving broad spectrum resistance of wheat.

Differential Display of Related Genes to Seed-coat Color by cDNA-SRAP in Brassica napus

MA Ai-Fen;LI Jia- Na;CHEN Li;QIAN Wei;FU Fu-You;LIU Lie-Zhao

Acta Agron Sin. 2008, 34(03):  526-529.  doi:10.3724/SP.J.1006.2008.00526

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The yellow-seed and black-seed in Brassica napus L. have different characters and different mechanisms in the seed color formation. The objective of this research was to explore the molecular mechanism of the differential expression between yellow and black immature seeds and demonstrate the feasibility of cDNA-SRAP for differential display. On the basis of the different lines with yellow and black seed-coat from recombinant inbred lines (RILs) which had self-pollinated for 7 generations, the yellow and black immature seed RNA bulked pools were constructed. SRAP was used to analysis the different cDNA pools transcribed from RNA pools. Totally, 2 100 amplifiedbands were obtained with 996 pairs of SRAP primer and the repeated bands were 65.2%. Twelve steady differential fragments with length of 100–300 bp between yellow and black immature seeds were acquired. Seven stable differential fragments were sorted out, cloned and sequenced. Sequence analysis revealed that only two of the fragments had significant homologous nucleotide sequence with Arabidopsis thaliana, one was similar to NAD+ADP-ribosyl transferase and the other was peptide transporter protein 3. The results indicated that cDNA pools with SRAP marker could be used for differential display on Brassica napus, and the two fragments may be related to the seed coat color expression of Brassica napus.

Rice Breeding for Resistance to Stripe Virus Disease

WANG Cai-Lin;ZHANG Ya-Dong;ZHU Zhen;ZHAO Ling;CHEN Tao

Acta Agron Sin. 2008, 34(03):  530-533.  doi:10.3724/SP.J.1006.2008.00530

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In order to improving the resistance to rice stripe virus disease of japonica rice, japonica varieties with high yield developed in Jiangsu province were crossed with Japanese varieties with resistance to rice stripe virus disease and good quality. The results showed that the resistance gene controlling rice stripe virus disease could be easily transferred from one variety to another one. It was effective to select resistant lines under natural conditions suitable for occurrence of stripe virus disease. Kantou 194 was a good parent for improving resistance to rice stripe virus disease and grain quality. Some breeding lines resistance to stripe virus have been developed through orientated selection for three generations and “Ning 4009” has been registered as “Nanjing 44” in Jiangsu province in 2007.

Mathematical Model of Multifactor Combination on Tissue Culture for Stylosanthes Cotyledon

ZHONG Jun;ZHENG Zhuo;ZHI Xun-Dan

Acta Agron Sin. 2008, 34(03):  534-538.  doi:10.3724/SP.J.1006.2008.00534

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Stylosanthes guianensis is regarded as one of the newest green leguminous forage in tropical and subtropical regions of China. It is a species of stylosanthes (Stylosanthes spp.), which has good traits including high dry matter yield, cold tolerance, anthracnose resistance and late maturity. But there were few reports on optimal media recipes for tissue culture in Stylosanthes guianensis. To investigate the main factors affecting tissue culture, callus was induced with a cultivar Reyan 10 (Stylosanthes guianensis cv.), surviving callus was cultured on different media after 2 weeks, then, the buds with 2–3 cm in length were regenerated on root induction medium after 3 weeks, finally they were transplanted into soil as the roots had formed after 2–3 weeks. Meanwhile the main medium components affecting the tissue culture were determined with orthogonal design, and mathematical model between the medium components and traits was established. The results was showed that there was a real regression relation between regulated factors and rate of callus induction, coefficient of bud differentiation, rate of root induction, with the equations of Y = 86.90+3.34X1+1.36X3+2.86X1X3, Y=7.70+1.52X2 and Y=299.30 +6.39X1+4.32X1X2 respectively. For callus induction, NAA was the most efficient factor, interaction between NAA and sucrose was the second factor, and sucrose was the last one. Also, the important factors were KT for bud induction as well as NAA and NAA/IAA for root induction.