Table of Content

12 June 2010, Volume 36 Issue 06

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Dense-Panicle-Related Gene Cloning from Rice Mutant A989 and Transgenic Plant Analysis

LI Ling, SHI Zhen-Ying, CHEN Ge-Zhi, WANG Xin-Qi, AN Lin-Sheng, ZHANG Jing-Liu

Acta Agron Sin. 2010, 36(06):  887-894.  doi:10.3724/SP.J.1006.2010.00887

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Rice (Oryza sativa L.) is a model monocotyledonous plant for genetic study due to its small genome size. Along with the completion of genome sequencing, gene cloning and function study becomes the most important task. The concomitant methodology of reverse genetics has played fundamental roles in identifying and studying rice genes in recent years. Rice heading time and inflorescence architecture are two inter-relating and agriculturally important characters. In Arabidopsis, TFL1 gene takes part in the configuration process and transition of growth stage, including flowering. In rice, there are four TFL1 gene homologies, RCN1-4, over-expression of any one of which could result in delayed flowering and abnormal inflorescence architecture. In this study, a mutant A989 with the character of dense panicle and late flowering was isolated from our T-DNA insertion population. Genetic and molecular analysis proved that in mutant A989, insertion of T-DNA nearby the RCN2 gene caused its over-expression, and resulted in the phenotype of dense panicle and late flowering. We further made RCN2 gene over-expressed driven by double 35S promoter, and analyzed characters of the transformants. Possible pathway of RCN2 gene function was discussed.

Analysis of Genetic Diversity and Tapping Elite Alleles for Plant Height in Drought-Tolerant Wheat Varieties

WEI Tian-Mei, CHANG Xiao-Ping, MIN Dong-Hong, JING Juan-Lian

Acta Agronomica Sinica. 2010, 36(06):  895-904.  doi:10.3724/SP.J.1006.2010.00895

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To make advances in wheat breeding, it is important to study germplasm diversity of winter wheat accessions, and identify SSR markers associated with important agronomy traits, for example plant height. Plant height reduction has observably contributed to the lodging resistance and yield increase of wheat in the last decades. In this study, we selected 136 historical winter wheat accessions planted in northern China and 117 SSR markers evenly distributing on the chromosomes of wheat to reveal the genetic diversity. A total of 1484 alleles of loci were detected from the accessions. The average alleles per locus were 12.6 which varied from 2 to 42. The polymorphism information content (PIC) value ranged from 0.016 to 0.941, with an average of 0.640. Most of the similar varieties were cultivated by the same breeders or belonged to the similar ecotype. Some of them were in accordance with the pedigree information. The most varieties cultivated in different ages were also clustered together. A total of 19 significant markers associated with plant height were identified (P<0.01) under drought stress. Among them, Xbarc168 (2D), Xgwm285 (3B), Xgwm126 (5A), Xgwm95 (2A), Xgwm212 (5D)and Xwmc396 (7B) were significantly associated with plant height (P<0.001). In well-watered environment, a total of 19 significant marker-trait associations were also identified (P<0.01), of which Xgwm285 (3B), Xgwm95 (2A), Xbarc125 (7D), Xgwm212 (5D), Xwmc396 (7B), Xgwm130 (2B) and Xgwm495 (4B) were strongly associated with plant height (P<0.001). 220, 181, 167, and 99 bp were the elite alleles of Xgwm285, Xgwm495, Xbarc125 and Xgwm212 for reducing plant height, respectively. With the rapid development of molecular biology and genomics, it is expected to utilize association analysis more widely in genetic research, germplasm enhancement and breeding in wheat.

Isolation and Analysis of MADS-box Gene from Soybean (Glycine max L. Merr.) Cytoplasmic Male Sterile Line

HAN Li-Chao, JIANG Wei, YANG Shou-Ping, YU De-Ti, GAI Jun-Yi

Acta Agron Sin. 2010, 36(06):  905-910.  doi:10.3724/SP.J.1006.2010.00905

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CMS (cytoplasmic male sterility) plays an important role in the utilization of crop heterosis. It is of important significance on theory and practice to study the genetic base and mechanism of CMS. To reveal the molecular mechanism of soybean cytoplasmic male sterility, we analyzed the gene differential expression between the soybean cytoplasmic male sterile line NJCMS2A and its maintainer line NJCMS2B by the cDNA-AFLP differential display method. A differentially expressed fragment from the flower buds of NJCMS2A was cloned and sequenced. The Blast results showed that the differentially expressed fragment shared 98.7% homology with g29510.1 cDNA fragment on Gm13 of soybean genome, and 98% homology with a MADS-boxgene of soybean. The Blast results of the amino acid sequences indicated that the differentially expressed fragment shared 96% homology with a MADS-box protein of Glycine max, 83% homology with the MADS-box M7 protein of Pisum sativum, 88% homology with the MADS-box 2 protein of Momordica charantia, and 83% homology with AGAMOUS protein of Gossypium barbadense. The structure and function prediction of the amino acid sequence showed that the protein encoded by the differentially expressed fragment was the transcription factor of the MADS-box gene which contained a typical K-box domain. The results of semi-quantitative RT-PCR showed that the expression quantity of the differentially expressed fragment in the flower buds of NJCMS2A was much higher than that of NJCMS2B. According to the above results, it was inferred that the differentially expressed fragment was probably related to the soybean cytoplasmic male sterility.

Cloning of Wheat TaPIM1 Gene and Analysis of Disease Resistance in TaPIM1 Transgenic Tobacco

ZHOU Xian-Yao, DONG Na, LIU Gong-Xia, ZHANG Fu-Yu, ZHANG Ceng-Yan

Acta Agron Sin. 2010, 36(06):  911-917.  doi:10.3724/SP.J.1006.2010.00911

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In plants,MYB transcription factors play various roles in developmental processes and in responses to biotic and abiotic stresses. In this paper, a pathogen-induced MYB gene of wheat, TaPIM1, protein TaPIM1 consisting of 323 amino acids. TaPIM1 protein contains two MYB DNA binding domains (R2, R3), two nuclear localization sites and two transcription activation domains. The entire sequence of TaPIM1 protein shares a low identity of below 43.69% with other plant MYB proteins. TaPIM1 is a new member of R2R3 type of MYB transcription factors of transcription families. The transcript of TaPIM1 was obviously upregulated after challenge with fungal pathogens Rhizoctonia cerealis or Bipolaris sorokiniana, respectively. The gene transformation vector pBI-35S:TaPIM1 was constructed, in which the TaPIM1 was driven by the CaMV 35S promoter. The vector pBI-35S:TaPIM1 wastransferred into tobacco cultivar W38 by Agrobacterium-mediated transformation method. Twelve TaPIM1 transgenic tobacco lines, such as M66, M102 and M110, were obtained through screening. The T₁ plants of these transgenic lines were subjected to PCR, RT-PCR analyses and evaluated for Ralstonia solanacearum resistance. The results showed that three transgenic lines, including M66, M102, and M110, overexpressed TaPIM1 and showed significantly enhanced resistance to R.  solanacearum compared with the host tobacco W38 plants.The resistance degree was correlated with the transcript level of the TaPIM1 inthese transgenic lines. These results suggested that TaPIM1 may positively modulate defense response to certain pathogens.was isolated from cDNAs of wheat leaves inoculated with Rhizoctonia cerealis. TaPIM1 gene encodes a

Analysis and Answers to Frequently Asked Questions in Quantitative Trait Locus Mapping

LI Hui-Hui, ZHANG Lu-Yan, WANG Jian-Kang

Acta Agron Sin. 2010, 36(06):  918-931.  doi:10.3724/SP.J.1006.2010.00918

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QTL mapping is an important step in gene fine mapping, map-based cloning, and the efficient use of gene information in molecular breeding. Questions are frequently met and asked in the application of QTL mapping in practical genetic populations. Questions related to statistical method of QTL mapping are: what does LOD score mean? What is the relationship between the reliability of detected QTL and the LOD threshold? How to evaluate different QTL mapping methods? How to improve the QTL detection power? Questions related to genetic parameter estimation are: how to calculate the phenotypic variance explained by each detected QTL? How to determine the source of favorable alleles at detected QTL? How efficient is the selective genotyping? Can composite traits be used in QTL mapping? Questions related to linkage map and mapping populations are: does the phenotype of a trait in interest have to follow a normal distribution? Does the increase in marker density greatly improve QTL mapping power? What effects will missing markers have in QTL mapping? What effects will segregation distortion have in QTL mapping? Our objective in this paper was to give an analysis and answer to each of the 12 frequently asked questions, based on our studies in past several years.

Integration of Mungbean(Vigna radiata) Genetic Linkage Map

DIAO Dan, CHENG Xu-Zhen, WANG Li-Xia, WANG Su-Hua, MA Yan-Ling

Acta Agron Sin. 2010, 36(06):  932-939.  doi:10.3724/SP.J.1006.2010.00932

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A high-density genetic linkage map with informative markers is essential for plant genome analysis, including gene mapping, identification of quantitative trait locus (QTL), map-based cloning, and physical map construction. One genetic linkage map of mungbean (Vigna radiata, 2n=2x=22) for the recombinant inbred line population (RIL) derived from an intersubspecific cross between a highly bruchid-susceptible cultivar Berken and a highly bruchid-resistant wild type ACC41 (V. radiata subsp. sublobata) was established. A total of 103 polymorphic SSR markers were screened from 701 pairs markers for density-enhancement of the previous map. Along with other marker data, a new genetic linkage map was constructed by using Mapmaker/Exp 3.0b, with 178 markers, including 96 SSR among which 90 locus from mungbean closely related species, 76 RFLP, four RAPD and two STS, spanning 12 linkage groups, covering total length 1 822.9 cM of the mungbean genome, with an average marker interval distance of 10.30 cM. In the study, we determined the SSR markers transferability of close relatives of mungbean including adzuki bean (Vigna angularis L.), black gram (Vigna mungo L.), common bean(Phaseolus vulgaris), cowpea (V. unguiculata) into mungbean genome. A total of 597 pairs SSR primers were tested and about 65%, 72%, 42%, 30% SSR markers above species respectively were effectively amplified in mungbean, indicating a certain degree of homology between these five genomes, and 97 pairs of polymorphic SSR screened from closely related species can be effectively used in the molecular genetic study of mungbean. Then the new map was compared with the map published for Azuki bean (Vigna angularis,2n=2x=22, n=11) using 32 SSR markers. Most of markers’ order in the two linkage maps was found to be highly conserved. However, chromosome rearrangement was occurred in two genomes after they diverged. In the new map, the major bruchid resistant gene was still mapped on LG I(9) with distances of less than 8.0 cM to the flanking markers, among which, the distance to SSR marker C220 which came from the LG 9 of common bean was less than 3.0 cM. Compared with the previous map, the mew location of the resistance gene is more closely linked with adjacent markers.

Construction of IF₂ Population and Its Application in Studies on Genetic Effects and Heterosis for Fiber Quality in Upland Cotton (G. hirsutum L.)

KONG Guang-Chao, QIN Li, XU Hai-Ming,ZHU Shui-Jin

Acta Agron Sin. 2010, 36(06):  940-944.  doi:10.3724/SP.J.1006.2010.00940

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Genetic analysis and heterosis prediction for fiber quality are very important in cotton breeding. An immotalized F₂ (IF₂) population with 188 combination F₁ in upland cotton was developed by random mating among recombinant inbred lines (RIL) derived from a intraspeciifc hybridization between HS46 and MARCABUCAG8US-1-88, and its fiber quality traits were evaluated. Based on the IF₂ population, we analyzed the genetic effects and heterosis of cotton fiber with the additive-dominance genetic model. The results showed that the values of all the five fiber quality traits, fiber length (FL), fiber uniformity (FU), fiber micronaire (FM), fiber elongation (FE) and fiber strength (FS), were distributed normally, and wider variations than those of its RIL population were found for the five fiber quality traits in the IF₂ population. The genetic dissection and heterosis prediction analyses indicated that a significant heterosis was found in fiber quality traits. The interaction effect between additive and environment played an important role in cotton fiber quality, following by the additive effect. Their heterosis was affected greatly by the environment effects, and there were significant difference between two environments in the experiment. All these results indicate that the IF₂ population is an ideal research population in genetic analysis and heterosis prediction for cotton fiber quality and other agronomic characters.

Isolation and Expression Analysis of a Drought-Induced Gene “ZmCKS2” in Maize (Zea mays L.)

ZHANG Zhong-Bao, LEI Min, LI Hui-Yong, ZHANG De-Feng, LIU Ying-Hui, Yun-Su, SONG Yan-Chun, WANG Tian-Yu, LI Yu

Acta Agron Sin. 2010, 36(06):  945-952.  doi:10.3724/SP.J.1006.2010.00945

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Plants respond to abiotic and biotic stresses through a number of biochemical and physiological reactions. Stresses inducible genes can be classified into two groups, i.e. functional genes that directly protect against stresses and regulator genes that regulate gene expression and signal transduction in the stress response. In our previous study, an EST from our drought related SSH library (suppression subtractive hybridization library) was obtained, which had a high similarity to AtCKS2in Arabidopsis. In the present study we cloned the cDNA homologous to CKS2, named ZmCKS2, by using in silico and homology-based cloning techniques. ZmCKS2 had an ORF of 267 bp and encoded 88 amino acids. The deduced protein of ZmCKS2 was predicted to contain a CKS (cyclin-dependent kinase regulatory subunit) structural domain, which was highly conserved in eukaryotes kingdom. The promoter of ZmCKS2 (about 2 kb upstream of ZmCKS2)was predicted to contain important regulatory elements including core promoter elements and drought, high salt, cold, ABA, light regulation, copper and oxygen responsive elements. Real-time quantitative PCR (qRT-PCR) analysis revealed that ZmCKS2 had different expression patterns in different organs. It was highly expressed in ears while its expression was very low in roots and leaves at seedling stage. qRT-PCR was also performed to investigate the expression profiles of the ZmCKS2 under different abiotic stresses such as drought, low temperature, high salt, MeJA (methyl jasmonate), and exogenous ABA (abscisic acid). Under drought or MeJA treatment, ZmCKS2 showed an up-regulated expression pattern. However, under cold or ABA treatment, the gene showed a down-regulation expression pattern. Under NaCl stress ZmCKS2 showed no obvious change. These results revealed that ZmCKS2 might be involved in multiple pathways of plants responding to different environmental conditions.

Cloning and Expression Analysis of aNovel Calmodulin Isoform TaCaM5 from Wheat

LIU Xin-Ying,WANG Xiao-Jie,XUE Jie,JIA Ning,DENG Lin,CA Gao-Lei,SHANG Chun-Lei,WEI Guo-Rong,HUANG Li-Li,KANG Zhen-Sheng

Acta Agron Sin. 2010, 36(06):  953-960.  doi:10.3724/SP.J.1006.2010.00953

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Calmodulin is a ubiquitous transducer of calcium signals in eukaryotes. It mediates a lot of cellular processes, such as transcription, cytoskeletal organization and motility, and amino acid metabolism. In diploid plant species, several isoforms of calmodulin have been described. A novel CaM gene was isolated from cDNA library of wheat leaves infected by Puccinia striiformis f. sp. tritici through RT-PCR approach. The gene was tentatively designated as TaCaM5 and encoded a novel CaM isoform based on protein sequence analysis. The open reading frame of TaCaM5 was 450 bp in length and 149 amino acids were encoded with four conserved EF-hand domains. TaCaM5, in which transmembrane domain or signal peptide sequence was absent, was predicted existing in cytoplasm. The amino acid sequence of TaCaM5 shares 97% identify with ZmCaM from Zea mays. TaCaM5 expressed differently in the wheat leaf, stem, and root. Challenged by stripe rust fungus(Puccinia striiformis f. sp. tritici), TaCaM5 was induced by this fungus in both incompatible and compatible interactions, with the maximal expression at 6 h and 24 h post inoculation respectively. TaCaM5 was up-regualted by exogenous abscisic acid, ethylene and jasmonic acid and down-regulated by salicylic acid. TaCaM5 was obviously up-regulated by various abiotic stresses, such as low temperature, mechanical wound, and drought. However, high salinity stress could not induce the expression of TaCaM5. These results suggest that TaCaM5 is probably involved in regulating the host defence responses through ethylene and jasmonic acid pathways, and also participate in Ca²⁺-CaM signal transmission pathways under mechanical wound, low temperature, and drought conditions.

Genetic Effects of Fiber Color in Brown-Cotton (Gossypium hirsutum L.)

FENG Hong-Jie,WANG Jie,SUN Jun-Ling,ZHANG Xin-Yu,GU Yin-Hua,SUN Jie,DU Xiong-Meng

Acta Agron Sin. 2010, 36(06):  961-967. 

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Color cotton is a type of cotton with natural fiber color, which meets demand of people who pursue to health and environment protection, but the cotton performs low yield, poor quality and monotone color in production. To solve these problems, in this paper, we analyzed the genetic effects for brown fiber, including the genetic correlation of brown-lint and brown-fuzz, and the different performances of fiber color in the F₁ of upland cotton (Gossypium hirsutum L.). Twenty cross combinations were obtained based on a complete diallel-mating system with two brown fiber and three white fiber lines of upland cotton. The fiber color was quantified by scanner and Photoshop based on the RGB parameters data of lint and fuzz. The genetic effects were predicted by the methods of MINQUE and AUP according to the ADM and AD models in QGAStation software. The results showed that the inheritance of fiber color was similar to that of fuzz color. Both of the addition and dominant effects were significant at 0.01 level of probability. The additive effect of the brown-lint was 0.8501, which was six times of its dominant effect. The additive effect of the brown-fuzz was 0.8726, which was eight times of its dominant effect. The correlation for genotype and phenotype between brown-lint and brown-fuzz was significant; with the genotype correlation coefficient between lint and fuzz colors was 0.9935. The additive effects of the five parents were significantly different, in which the effect of brown cotton was positive, but that of white cotton was negative. It indicated that the genetic variation of the brown-lint and brown-fuzz in upland cotton was mainly derived from additive and dominant effects, in which the additive effect was predominant, and there were linkage and interaction between the inheritances of lint and fuzz color. The different fiber colors of F₁ were resulted from the different additive effects of different varieties or lines.

Analysis of Differentially Expressed Genes in Oleic Acid Synthesis of Brassica napus by Gene Chip

GUAN Mei, LI Xun, GUAN Chun-Yun

Acta Agron Sin. 2010, 36(06):  968-978.  doi:10.3724/SP.J.1006.2010.00968

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The oil from rapeseed with high oleic oil content is insensitive to oxidation and longer shelf life. In daily diet high oleic acid oil can reduce low-density lipoprotein cholesterol levels in blood and prevent arteriosclerosis. In addition, high oleic acid content in edible oil is an important fat indicator. Oleic acid can be effectively converted to methyl ester and is beneficial to produce biodiesel. Oleic acid content in conventional rapeseed is only 17%. However, oleic acid content in low erucic acid rapeseed reaches around 60%. Differential expressed genes of oleic acid have been found in thehigh oleic acid line (71.71%) and low oleic acid line (55.6%) of Brassica napus by gene chip technic. The results showed that there were 562 differential expressed genes relating to high and low oleic acid contents in rapeseed, among them 194 were up-regulated genes and 368 were down-regulated genes. The up-regulated gene (NM_100489) and the down-regulated gene (NM_130183) were then taken as the materials. Real time RT-PCR was further used to confirm the results of gene chip, and the results of real time RT-PCR analysis agreed with the results by gene chip. According to the results of gene chip, 562 differentially expressed genes were annotated functionally by Go Annotation System. The molecular function of differential expressed genes mainly included catalysis of enzymes, binding, transcriptional regulation, metabolism and others which were unknown. Some genes relating to sugar metabolism and fatty acid synthesis were identified as differential expressed genes. They are pyruvate kinase, fructose diphosphate, acyl transfer/acyl-ACP S lipase, hydrolase acting on ester bond, D9 stearoyl acid-N-carrier protein desaturase (ADS1), D9 acyl-lipid desaturase 2 (ADS2), ω-3 fatty acid desaturation enzymes (fad3) and so on.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

A Robust and Cost-Effective SGOC Method for Testing Rice Iron Concentration in Biofortified Breeding

JIA Qian, XU Qin,HU Xia,SUN Yong, CHENG Li-Rui,ZHOU Zheng,ZHU Ling-Hua,ZHAO Q

Acta Agron Sin. 2010, 36(06):  979-987.  doi:10.3724/SP.J.1006.2010.00979

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Iron is an important micro-nutrient to human health. Malnutrition of iron is a serious problem associated with resource poor population of many developing countries. Development and consumption of iron-rich rice varieties are considered one of the ways to solve the problem. To facilitate large-scale screening of breeding materials for iron concentration in the rice iron-biofortified breeding program of China, we developed a new method “surging and grind-milling of orthophenanthroline colorimetry testing” (SGOC). Based on the testing results of 3 sets of 84 diverse rice genotypes that differ greatly in grain iron concentration, the correlation coefficient was as high as 0.87 between the SGOC method and the standard ICP-MS testing method. The per sample cost of the SGOC method was about 0.1$, or 50 times less the ICP-MS method, indicating that the SGOC method is a robust, fast and cost-effective, particularly useful for preliminary screening of the iron concentration of large numbers of early generation breeding materials. Our results demonstrated that milling and polishing with iron-made equipment tended to significantly increase the iron concentration of processed rice, which was also eliminated in the SGOC method. Finally, our results on the 59 BC progeny indicate that introgression of genes/ QTLs for high iron concentration from high iron rice germsperm into elite local rice varieties is an efficient way to develop high yielding rice varieties with significantly improved rice iron concentration in future rice biofortified breeding.

Antioxidant Property of Naked Oat Core Collections

REN Yi,PING Hua,REN Gui-Xing

Acta Agron Sin. 2010, 36(06):  988-994.  doi:10.3724/SP.J.1006.2010.00988

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Naked Oat (Avena nuda L.) originated in China, has a high values in nutrition and medicine. Besides dietary fiber and nutrients, various natural antioxidants, such as phenolic compounds, phenolic acids, avenanthramides (unique to oats) and phytosterols are also contained in naked oat. All these compounds possess potential health-promoting properties, partly attributing to their antioxidant activity. Up to now, China has built the core of naked oat germplasm with the greatest diversity of naked oat types. The objective of this study was to determine the total phenol (TP), total avenanthramides (TAV), β-glucan contents and the antioxidant activity of oat cultivars from main productive areas of China as well as Former Soviet Union and North America. The correlation of antioxidant activities with contents of these components was also statistically investigated, which is benefit for oat breeding. The antioxidant activities, contents of TP, TAV, and β-glucan of 120 naked oat accessions were evaluated by Folin-Ciocalteu method, HPLC analysis and enzymatic method, respectively. Meanwhile, the antioxidant capacity was determined by 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH) scavenging ability method. Significantly genotypic variations were observed, and contents of TP, TAV, and β-glucan were 4.34–179.98 mg L^-1, 250.99–807.88 mg kg^-1, 25.21–347.55 mg kg^-1, and 0.59–9.69% respectively. The 120 accessions were clustered into six groups using K-mean cluster method, which consisted of 20, 39, 2, 22, 12, and 25 accessions respectively. There were significantly positive correlations between antioxidant activity and the contents of TP and TAV. However, the correlation between β-glucan and DPPH was not significant. These results indicated that avenanthramides contributed greatly to the antioxidant property in naked oat grains. A relative wide variations in TAV and TP contents and compositions were mainly due to differences among cultivars. Duji from Sichuan province and Yumai 38 from Qinghai province with high contents of TP and TAV are expected to be used in further quality breeding of naked oat.

Effects of ADP-Glucose Pyrophosphorylase Activity on Sterility and Development of Grain in K, V, and T-Cytoplasmic Male Sterile Lines in Wheat

WU Shi-Wen,GAO Qing-Rong,SUN Zhe,WANG Mao-Ting,SUN Zheng-Juan,YUAN Kai,YU Song

Acta Agron Sin. 2010, 36(06):  995-1002.  doi:10.3724/SP.J.1006.2010.00995

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Cytoplasmic male-sterile (CMS) lines, especially K (Aegilops kotchyi), V (Aegilops ventricosa), and T (Triticum timopheevi) types of cytoplasms, are of high value in heterosis utilization in wheat (Triticum aestivum L.). The sterile mechanisms of these CMS types have been focused in hybrid wheat research. As a key and rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGPase) is considered to play an important role in the sterility of CMS lines. For gaining an insight into the physiological basis of the sterility in CMS lines of wheat, the activities of AGPase in leaves, young spikes, and grains were measured in K, V, and T types of isogenic CMS lines (Ji 5418 background) at different growth stages, and compared with those of their maintainer line. The dynamic accumulations of starch, amylose, and amylopectin were also investigated in both superior (the first and the second grains in a spikelet) and inferior (grains except for the first and the second grains in a spikelet) grains. In young spikes, the AGPase activities of the three CMS lines were significantly higher (F = 133.81, P < 0.0001) with the differences of 9.33 - 27.94 μmol g^-1 FW h^-1 at floret primordium stage, and significantly lower (F = 13.97 - 75.20, P < 0.0001) by 4.27 - 7.44 μmol g^-1 FW h^-1 at tetrad stage as compared with the maintainer line. From floret primordium to tetrad stage, the CMS lines had continuously higher level of AGPase activities in leaves than the maintainer line, with the differences ranged from 7.39 to 80.77 μmol g^-1 FW h^-1 (F = 135.76 - 5454.28, P < 0.0001). Compared with the maintainer line, the three CMS lines all presented lower accumulations (P < 0.05) of starch, amylose and amylopectin in grain. The starch content and AGPase activity in superior grains were significantly higher than those in inferior grains for CMS lines. The dynamic accumulations of starch in superior and inferior grains fitted Logistic equations, and positively correlated with the starch accumulation rate (r = 0.4460 - 0.7150, P = 0.0004 - 0.0487). The AGPase activity in leaves had an insignificantly negative correlation with net photosynthetic rate. In conclusion, the male sterility is probably in relation to the insufficiency of energy in leaves and young pikes at floret primordium stage resulting from the high AGPase activity, and the low accumulation of starch in pollens at tetrad stage caused by low AGPase activity in young spikes. The sterile cytoplasm has a negative effect on AGPase activity, resulting in decreases of ADPG level and starch accumulation in grains. Besides, the negative effect of AGPase activity on net photosynthetic rate in flag leaves may result in unfilled grains in CMS lines.

Relationship of Photosynthetic Carbon Assimilation Related Traits of Flag Leaves with Yield Heterosis in a Wheat Diallel Cross

WANG Xiu-Li,HU Zhao-Rong,PANG Hui-Ru,DU Jin-Kun,SUN Qi-Xin,WANG Min,NI Zhong-Fu

Acta Agron Sin. 2010, 36(06):  1003-1010.  doi:10.3724/SP.J.1006.2010.01003

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In spite of commercial use of heterosis in agriculture, the physiological basis of heterosis is poorly understood. Photosynthetic carbon assimilation related traits of flag leaves, including photosynthetic capacity, stomatal conductance, intercellular CO₂ concentration, transpiration rate, water use efficiency and efficiency of primary conversion of light energy, were measured at early, middle, and post grain-filling stages in a wheat (Triticum aestivum L.) diallel cross involving 20 hybrids and nine parents, with the purpose of determining the relationship of yield heterosis with these traits. The magnitude of heterosis varied subject to cross combination, trait, and developmental stage. Further analysis indicated that heterosis of photosynthetic carbon assimilation related traits was not correlated with that of spike length and effective spike per plant, but significantly correlated with that of other yield components. Moreover, at middle grain-filling stage, the heterosis of photosynthetic rate, intercellular CO₂ concentration, water use efficiency and efficiency of primary conversion of light energy were significantly and positively correlated with those of fertile spikes per plant, thousand grain weight, yield per plant and yield of main stem, suggesting that higher photosynthetic capacity and water use efficiency could be one of the important physiological basis of wheat hybrid vigor.

Differences of Plant-Type Characteristics between Rice Cultivars with High and Low Levels in Yield and Nitrogen Use Efficiency

Acta Agron Sin. 2010, 36(06):  1011-1021.  doi:10.3724/SP.J.1006.2010.01011

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A field experiment with 225 kg ha^-1 N fertilizer application was carried out in 2006 and 2007 on the farm of Yangzhou university, Jiangsu province, China. Using 12 rice genotypes (six N-efficient and six N-inefficient) selected from 120 rice cultivars grown in Yangzhou during 2004 and 2005 to investigate the relationship among the plant-type characteristics, N use efficiency and yield performance. The results showed that the top three leaves length and drop-angle of high yield and N-efficient rice genotypes were 9.29%, 65.3% lower than those of the low yield and N-inefficient ones, and the width of the top three leaves, population LAI, valid LAI, high valid LAI and LW/LA(leaves weight/leaves area) of the former of were 29.25%, 8.27%, 13.32%, 6.66%, and 5.82% higher than those of the latter on average respectively. The high yield and N-efficient genotypes had higher lodging resistance capability and more reasonable distribution for the length of internodes on stem than the low yield and N-inefficient ones. Yield and N use efficiency negatively correlated (significantly at P<0.05 or P<0.01) with the length and drop-angle of the top three leaves, while positively correlated(significantly at P<0.05 or P<0.01)with the width of the top three leaves, population LAI, valid LAI, high valid LAI, SLW, anti-broken strength, bender moment, and lodge index. Especially, the length and width of the flag and top 3rd leaves played an important role in the N use efficiency. It was indicated that good plant-type structure is a prerequisite for N use efficiency.

Effects of Plant Density, Nitrogen Application, and Water Stress on Yield Formation of Maize

XUE Ji-Quan,ZHANG Ren-He,MA Guo-Sheng,LU Hai-Dong,ZHANG Xing-Hua,LI Feng-Yan,HAO

Acta Agron Sin. 2010, 36(06):  1022-1029.  doi:10.3724/SP.J.1006.2010.01022

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 It is important to promote adaptability of maize varieties to high-density, low nitrogen and drought stresses so as to improve maize yield. Six maize varieties of Yuyu 22, Shaandan 902, Jingdan 28, Shaandan 8806, Xianyu 335 and Zhengdan 958 were planted under two kinds of densities (45 000 and 75 000 plants ha^-1), pure nitrogen levels (112.5 and 337.5 kg ha^-1) and water treatments (controlling water at prophase and normal irrigation) in fields to elucidate effects of stresses (high density, low nitrogen and drought) on yield formation of maize varieties. Main physiological parameters of source-sink characters The results showed that differences of grain yield were little among maize varieties under less environmental pressure (low density, high nitrogen and normal irrigation), while these were significant under stress (high density, low nitrogen and drought). Changes of source characters (LAI, P_n of ear leaves and source capacity), sink characters (sink capacity of population), harmonious source-sink characters (sink-source ratiograin yield. There were significantly positive correlations between grain yield and LAI, source capacity, dry matter accumulation at maturity, dry matter accumulation from silking stage to maturity, sink capacity of population and HI. To improve maize yield, we should strengthen artificial selection for adapting to natural selection, improve source-sink characters of maize population under stress, enhance leaf photosynthetic efficiency from silking stage to maturity, strengthen source and promote sink, and improve production capacity and adaptability under stresses., grain filling rate and HI), dry matter accumulation at maturity and dry matter accumulation from silking stage to maturity showed the same rules as and grain yield were measured.

RESEARCH ACTIVITIES

Correlation of Root Physiology and Leaf Photosynthesis Characteristics in Northern Chinese Japonica Super Rice

XU Ming,JIA De-Tao,MA Dian-Rong,WANG Jia-Yu,MIAO Wei,CHEN Wen-Fu

Acta Agron Sin. 2010, 36(06):  1030-1036.  doi:10.3724/SP.J.1006.2010.01030

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Two typical japonica super rice cultivar Shennong 265 and Shennong 606 were used as experimental materials and Akihikari and Liaojing 294 as control cultivation.Root physiological activity and leaf photosynthetic capability of Northern Chinese Japonica Super Rice were measured in pot experiment. At every stage of root development, total absorption area, active absorption area, root oxidizing ability per plant, and bleeding rate in Shennong 265 and Shennong 606 were significantly higher than control cultivar. During the filling stage, Shennong 265 and Shennong 606 roots showed slower roots senescence and stronger physiological activity than the control. During the filling period both chlorophyll degradation rate and photosynthetic rate of Shennong 265 and Shennong 606 were significantly slower than those of control cultivar. Furthermore, root physiological activities showed a positive correlation with leaf chlorophyll content in Japonica Super Rice during filling periods, showing that Shennong 265 and Shennong 606 had advantages in root physiology and leaf photosynthesis characteristics compared with Akihikari and Liaojing 294.

Relationship of Mixograph Parameters with Farinograph and Extensograph Parameters, and Bread-Making Quality Traits

SHEN Xiao-Yong, YAN Jun, CHEN Xin-Min, ZHANG Yan, WANG De-Sen, HE Zhong-Hu, ZHANG Yong

Acta Agron Sin. 2010, 36(06):  1037-1043.  doi:10.3724/SP.J.1006.2010.01011

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Prediction of end-use quality using parameters from simple testing instruments as Mixograph is critical for efficient selectionin breeding programs for wheat (Triticum aestivum L.) quality improvement. In this study, 241 wheat cultivars and advanced lines were sown in Beijing, Jinan, Anyang, and Zhengzhou, China from 2002 to 2009 growing seasons. The Mixograph parameters of these cultivars were measured for determining their associations with Farinograph and Extensograph parameters, and bread-making quality traits. The multiple stepwise regression analysis revealed that Farinograph stability time, Extensograph maximum resistance and energy area, and bread score could be efficiently predicted by Mixograph midline peak value, peak width, peak integral, time x value, and tail value, which accounted for 61.0–68.0% of the phenotypic variation, with the fitting degrees of 0.83 and 0.95 for the model of Farinograph stability time and Extensograph energy area, respectively. Farinograph water absorption and development time, Extensograph extensibility, and loaf volume could be predicted by Mixograph midline peak value, peak width, peak integral, right value, right integral, and time x integral, accounting for 46.0 - 55.0% of the phenotypic variance. The Midline peak integral presented as the most important parameter for predicting Extensograph maximum resistance and energy area, and explained 58.7% and 59.7% of the variances, respectively. Midline peak integral and peak value were the two most important parameters when using Mixograph for quality testing.

Effect of Calcium on Maize Seedling Root Hydraulic Conductivity and Growth under Water Stress and Rehydration Conditions

WU Yan, ZHANG Sui-Qi, LIU Xiao-Fang, SHAN Lun

Acta Agron Sin. 2010, 36(06):  1044-1049.  doi:10.3724/SP.J.1006.2010.01044

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The effects of extra calcium (additions of 10 mmol L^-1 CaCl₂ into half-strength Hoagland solution) on maize (Zea mays L.) seedling root hydraulic conductivity (Lp_r), morphology and leaf water potential (ψ_w) were investigated under water stress, which was simulated by 10% PEG-6000 with osmotic potential (ψ_{s) value of -0.2 MPa for seven days, and subsequent two days rehydration. Whole root hydraulic conductivity (Lpr) and leaf water potential (ψw) were determined by pressure chamber. After these treatments, it could be seen that water stress reduced Lpr, which was restored when calcium was added to the solution for growing the water-stressed plants. In addition, the Lpr recovered to the level of the control after re-watering at high Ca²⁺ level, but the recovery of Lpr was only 59.06% at regular Ca²⁺ level. HgCl2 (50 μmol L^-1) treatment caused a sharp decline in Lpr, which was almost restored by treatment with 5 mmol L^-1 β-mercaptoethanol. The reduction of Lpr by Hg²⁺ was 53.20% and 74.55% at regular and high calcium levels, respectively under water stress condition, and 62.1% under normal condition. The results suggest that Ca²⁺ increased the passage of water through the cell membrane of roots by increasing the activity of Hg-sensitive AQP under water stress. The percentage of reduction by Hg²⁺ was decreased to the control level two days after re-watering in CaCl2 treated plants. The leaf water potential was declined significantly under water stress, particularly at regular calcium level with respect to the decrease of Lpr. However, ψw recovered rapidly onw day after re-watering. Furthermore, water stress had a detrimental effect on the root growth. The addition of calcium, especially at low water potential, increased the root surface area and primary root diameter, and it promoted primary root enlongation and lateral root development. Compared with the controls, the growth of Ca treated plants was recovered gradually with the prolonging of rehydration. Therefore, these results indicated that the extra calcium, with respect to root growth and water uptake, mitigates the negative effect of water stress and enhances the compensatory effects of rehydration.}

Genetic Analysis and Gene Mapping of a Novel Yellow-Green Leaf Mutant in Rice

LI Xiu-Lan, SUN Xiao-Qiu, WANG Ping-Rong, ZHOU Hui, DENG Xiao-Jian

Acta Agron Sin. 2010, 36(06):  1050-1054.  doi:10.3724/SP.J.1006.2010.01050

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An inherited stably yellow-green leaf mutant D83 was isolated by chemistry mutagenesis. Its whole plant exhibited yellow-green character at the seedling stage, and gradually changed into pea green from the tillering stage. Compared with its wild-type parent 10079, at the seedling stage, the contents of chlorophyll a, chlorophyll b and carotenoid decreased by 45.03%, 53.93% and 39.56%, at the maturation period, the number of spikelets per panicle reduced by 9.45%, the 1000-grain weight by decreased 10.76%, respectively. Genetic analysis of F₁ and F₂ generations of D83 crossed with green rice varieties showed that the yellow-green leaf character was controlled by one pair of recessive nuclear genes. Genetic mapping of the mutant gene was conducted by using molecular marker and F₂ mapping population of D83/Zhefu802. The results suggested that the mutant gene of D83 was mapped on the short arm of rice chromosome 2, nearby SSR marker RM110, between InDel markers Ch2-27 and Ch2-32. The genetic distances from the target gene to two InDel markers were 1.2 cM and 2.3 cM, respectively. The mutant gene of D83 was considered to be a new yellow-green leaf gene in rice and designated tentatively as chl13(t).

Effects of Phosphorus Fertilizer on Accumulation of High Molecular Weight Glutenin Subunits and Glutenin Macropolymer Size Distribution in Wheat Grain

NI Ying-Li, WANG Zhen-Lin, LI Wen-Yang, YAN Su-Hui, YIN Yan-Ping, LI Yong, WANG Ping, CHEN Xiao-Guang

Acta Agron Sin. 2010, 36(06):  1055-1060.  doi:10.3724/SP.J.1006.2010.01055

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For gaining insights into the relationship between the accumulation of high-molecular-weight glutenin subunit (HMW-GS) and the distribution of glutenin macropolymer (GMP) in wheat (Triticum aestivum L.), Shannong 12, a cultivar with high glutenin, was used in a field experiment with four phosphorus (P) application levels (0, 40, 100, and 160 kg ha^-1) under low nitrogen (112.5 kg ha^-1) and normal nitrogen (225 kg ha^-1) conditions, respectively. The result showed that HMW-GS in grains formed before 14 d after anthesis, and its content at maturity was higher in P application treatments than in the treatment with no P fertilizer applied. Phosphorus was in favor of the accumulation of HMW-GS under the low nitrogen (N) condition, but caused a negative effect in high P levels under the normal N condition. The content of GMP particle in <10 μm in diameter was significantly reduced with increasing P application. The effect increased with increasing P level under the low N condition, but showed the largest reduction at P level of 100 kg ha^-1 and the smallest reduction at P level of 40 kg ha^-1. For GMP particle in 10–100 μm and >100 μm groups, their contents tended to increasing with more P applied under both N conditions. Under the normal N condition, there was no significant effect of P level on the number distribution of GMP particle. At maturity, the content of HMW-GS was negatively correlated with the volume of GMP particle in <10 μm group, but positively correlated with that in 10–100 µm group. The result suggested that larger GMP particles have higher HMW-GS content than the smaller GMP particles.