Table of Content

12 July 2012, Volume 38 Issue 07

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REVIEW

Facing toward Challenges and Corresponding Strategies for Maize Breeding in Southwestern Region of China

PAN Guang-Tang，YANG Ke-Cheng

Acta Agron Sin. 2012, 38(07):  1141-1147.  doi:10.3724/SP.J.1006.2012.01141

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This article is based on the analysis of facing challenges of maize industry development in the Southwest of China to find the major gap affecting Southwestern maize breeding outcome, and propose appropriate strategies and ways according to the development of domestic and abroad maize hybrid breeding trends and our physical practice. Breeding objectives should be focused on enhancing disease resistance and pest-resistance, drought-tolerance and tolerance to poor soil fertility, and being available to fit complete mechanization of production and cultivate management system reform, as well as promoting the breeding and utilization of new “forage maize” crop with good vegetative superiority. Germplasm enhancement should clearly define heterotic group where it belongs to, simplify heterotic pattern, systematically develop basic germplasm evaluation and analysis, synthesize and improve breeding population, and create new specific breeding materials. Breakthrough inbred line breeding, should be focused on the exploration and utilization of specific new genes, using GCA yield as an important selection criteria, selecting those plant lines with slower inbreeding depression as the primary selection object alternatively, using selfing, sister mating, or mixed pollen mating, increasing frequency of good genes or genotypes, and increasing the power for selection and identification with yield test. Improved breeding methods include increasing plant density, increasing selection pressure, implementation of the North-South shuttle breeding, speeding up the construction of maize seed production base in southern China, at the same time speeding up the application of high and new technology in corn breeding.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Polymorphism of Starch Granule-Associated Proteins and 5′ Leader Sequence of GBSSI Gene in Indigenous Naked Barley (Hordeum vulgare L.) from Qinghai-Tibetan Plateau in China

WANG Chun-Ping,GAO Li-Juan,PAN Zhi-Fen,NIMA Zha-Xi,TANG Ya-Wei,ZENG Xing-Quan,LI Qiao,DENG Guang-Bing,LONG Hai,YU Mao-Qun

Acta Agron Sin. 2012, 38(07):  1148-1154.  doi:10.3724/SP.J.1006.2012.01148

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Starch granule-associated proteins (SGAPs) are minor components tightly bound with starch granules, most of which are believed to be starch biosynthetic enzymes. We separated SGAPs from 261 indigenous naked barley accessions in Qinghai-Tibetan Plateau of China using 1D-SDS-PAGE technique. A total of 20 polymorphic banding patterns with molecular weights of 45–100 kD and 78 SGAPs patterns were detected, of which bands 2, 3, 5, 10, and 11 were novel protein bands. The 5′ leader sequences of GBSSI gene were cloned using 236 accessions of indigenous naked barley. Two types of length polymorphisms (1 000 bp and 800 bp) were found with frequencies of 80.1% and 19.9%, respectively. According to sequencing results, there were 32 polymorphic sites in the 5′ leader sequences of GBSSI gene, including nine InDels and 23 SNPs. Specific mutations were found in Qinghai-Tibetan Plateau accessions. For example, the 400 bp deletion reported corresponding to low amylose content in barley was absent in this study; and special SNPs were detected in accessions yf127, yf70, 011Z1396, and 09Z586. These results imply that the SGAPs of the Qinghai-Tibetan Plateau indigenous naked barley are abundant and polymorphic. The novel sequence characteristics in the GBSSI5′ leader sequence of the low amylose accessions suggest a different mechanism for amylose biosynthesis in Qinghai-Tibetan Plateau indigenous naked barley.

Distribution of Allelic Variation for Vernalization, Photoperiod, and Dwarfing Genes and Their Effects on Growth Period and Plant Height among Cultivars from Major Wheat Producing Countries

YANG Fang-Ping,XIA Xian-Chun,ZHANG Yong,ZHANG Xiao-Ke,LIU Jian-Jun,TANG Jian-Wei,YANG Xue-Ming,ZHANG Jun-Ru,LIU Qian,LI Shi-Zhao,HE Zhong-Hu

Acta Agron Sin. 2012, 38(07):  1155-1166.  doi:10.3724/SP.J.1006.2012.01155

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To efficiently use exotic resources in Chinese wheat breeding programs, we investigated the heading date, maturity date, and plant height of 100 representative cultivars collected from 14 countries at eight locations in China, and detected the allelic variations of vernalization loci VRN-1 and VRN-B3, photoperiod gene Ppd-D1a,and dwarfing genes Rht-B1b and Rht-D1b by means of molecular markers. The frequencies of vernalization loci were 8.0% for Vrn-A1a, 21.0% for Vrn-B1, 21.0% for Vrn-D1 and 64.0% for vrn-A1+vrn-B1+ vrn-D1, except for the absence of dominant allele Vrn-B3 in all tested materials. Dominant vernalization alleles Vrn-A1a, Vrn-B1, and Vrn-D1 were mainly observed in cultivars from Chinese spring wheat region, Italy, India, Canada, Mexico, and Australia; whereas, cultivars carrying all recessive alleles at the four vernalization loci and vrn-A1+vrn-D1+Vrn-B1+vrn-B3 genotypewere mostly found in cultivars from Chinese winter wheat region, United States (US) winter wheat region, Russia winter wheat region, United Kingdom (UK), France, Germany, Romania, Turkey, and Hungary. All cultivars headed normally when sown in autumn. Cultivars with dominant alleles showed earlier heading date than those with recessive alleles, and genotypes with two or more dominant alleles showed additive effects. Some European and US cultivars with recessive genes at the four vernalization loci could not mature in Yangling and Chengdu. Under spring-sown condition, the cultivars with dominant vernalization alleles showed high heading frequency; in contrast, most cultivars with recessive alleles failed to head. Gene Ppd-D1a was distributed mainly in cultivars from China, France, Romania, Russia, Mexico, Australia, and India with the total frequency of 68%. Most cultivars with Ppd-D1b were from high latitude regions, such as UK, Germany, Hungary, and Canada. The Ppd-D1a genotypes appeared to head earlier than the Ppd-D1b genotypes. Daylight condition had no effect on maturity of most Ppd-D1a genotypes, but short daylight condition resulted in failing mature in most Ppd-D1b genotypes. The frequencies of dwarfing genes Rht-B1b and Rht-D1b were 43.0% and 35.0% in the cultivars tested, respectively. Rht-B1b was mainly observed in cultivars from US, Romania, Turkey, Italy, Mexico, and Australia, while Rht-D1b had high frequency in varieties from China, Germany, UK, Italy, and India. Generally, cultivars from one country contain either Rht-B1b or Rht-D1b, andthe frequencies of Rht-B1b and Rht-D1b were very low in cultivars from high latitude regions. The effect of Rht-B1b, Rht-D1b and Ppd-D1a on reducing plant height was significant, of which Rht-B1b and Rht-D1b exhibited an additive effect.

Sequence Analysis of Δ⁹-Stearoyl-ACP Desaturase Gene (SAD) in Peanut

DONG Jin-Yu,WAN Yong-Shan,LIU Feng-Zhen

Acta Agron Sin. 2012, 38(07):  1167-1177.  doi:10.3724/SP.J.1006.2012.01167

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The peanut (Arachis hypogaea L.) cultivars are an allotetraploid consisting of A and B genomes. Δ⁹-Stearoyl-ACP desaturase (SAD) is a key enzyme that catalyzes the conversion of stearoyl-ACP to oleoyl-ACP, and finally controls the content of oleic acid as well as the proportion of saturated to unsaturated fatty acids. By using the primers based on the peanut cDNA sequence of SAD (AF172728), genomic DNAs were amplified from the wild diploid species A. duranensis and A. ipaensis, and from the cultivated accessions of peanut Fenghua 2, Shanhua 7 and Puyangdatuoyang, respectively. Two isoforms of the genomic SAD were identified and named as FhgSAD-1 and FhgSAD-2 from the cultivated peanut accessions. In addition, two isoforms of SAD cDNA were isolated and named as FhrSAD-1 and FhrSAD-2 from Fenghua 2. Comparison of the genomic sequences with cDNAs revealed that there were two introns in the SAD genomic sequences. Sequences alignment showed that the similarity between FhgSAD-1 and FhgSAD-2 in nucleotide level was over 97.5%, with 69 different sites in total, including 62 SNP sites and six variation sites of endonuclease recognition. The cDNA sequence similarity between FhrSAD-1 and FhrSAD-2 was 98.6%, with 98.9% nucleotides identity in coding region. Deduced amino acid sequences revealed that only one difference occurred in serine gathering area of ¹⁷PSSSSSSSSSSFSL³⁰. gSAD-1 shared 99.9% nucleotide sequence homology with gSAD-A, while gSAD-2 was the same as gSAD-B. According to the phylogenetic tree, it is assumed that gSAD-1 and gSAD-2 may come from the A and B genome, respectively. The results revealed the characteristics of SAD sequences from different genomes of peanut, and provided important basis for exploring gene expression regulation and fatty acid component improvement in peanut seeds.

Rice Pyramiding Breeding using Sheath Blight Resistance QTL qSB-9^TQ and Stripe Disease Resistance Gene Stv-bⁱ

CHEN Zong-Xiang,ZUO Shi-Min,ZHANG Ya-Fang,ZHU Jun-Kai,WANG Long-Ping,FENG Fan,MA Yu-Yin,PAN Xue-Biao

Acta Agron Sin. 2012, 38(07):  1178-1186.  doi:10.3724/SP.J.1006.2012.01178

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Indica rice cultivar Teqing and japonica rice cultivar Zhendao 88 were used as the donor parents with the sheath blight (SB) resistance QTL qSB-9^TQ and the resistance gene Stv-bⁱ, respectively. Commercial rice japonica cultivars, Wuyujing 3 and Wujing 15, were used as the receipt parents to cross and backcross with the donor parents, respectively. Flanked polymorphic markers to the two loci were developed and employed to select the target loci via marker assisted selection (MAS) in each backcross and self-cross progeny. Till backcross generation BC₄F₁, pyramiding was performed by crossing the selected individuals with different integression genes. At F₃ generation, the pyramiding lines with homozygosity at both gene loci were obtained. Results of disease resistance evaluation indicated that both pyramiding lines were resistant to stripe disease, and increased resistance to SB with a reducing SB sating of 1.1–1.6 in Wuyujing 3 background and 0.8–1.4 in Wujing 15 background based on a “0–9” SB rating scale. Combining the results of resistance phenotype at the low backcrossing generation, we thought the markers developed in this study were efficient in selecting the two genes by MAS. Some questions associated with SB resistance breeding and pyramiding breeding via MAS were discussed.

Cloning of Granule-Bound Starch Synthase Gene and Construction of Its RNAi Vector in Potato Tuber

LIU Yu-Hui,WANG Li,YANG Hong-Yu,YU Bin,LI Yuan-Ming,ZHANG Jun-Lian,WANG Di

Acta Agron Sin. 2012, 38(07):  1187-1195.  doi:10.3724/SP.J.1006.2012.01187

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There is about 17% starch in potato (Solanum tuberosum L.) tubers. Potato starch granules are composed of two polysaccharides, unbranched amylose (approximately 20% to 25%) and branched amylopectin (approximately 75% to 80%). To develop transgenic potato with high-amylopectin in tubers, we got a cDNA sequence of the potato GBSSI from the total RNA of potato tubers by RT-PCR using specific primers of conserved domain of GenBank Accession Number X58453 sequence.The GBSSI cDNA sequence shared 99.78% similarity with the GBSSI gene in GenBank (accession No. X58453). The full-length of cDNA was 1 824 bp, which contained 607 amino acids, three conserved domains and many important functional sites. The 3D structure of GBSSI was highly similar to that of the glycogen synthase, indicating that GBSSI has a function of starch synthesis. GBSSI similar gene obtained here was granule-bound starch synthase, and its sequence was submitted to GenBank, with the accession number of EU403426. On the basis of a 542 bp RNAi target region from the CDS of GBSSI, the sense and antisense fragments were amplified and separated by a 237 bp intron to construct the RNA interference expression vector pBI121g-PgABI containing “sense gbssA-VP1-ABI3-like protein intron-antisense gbss B” regulated by Patatin promoter, which will lay a solid foundation for the study on synthesis of starch and breeding of transgenic potato with high amylopectin content or pure amylopectin.

Relationship of Leaf Shape, Pod Traits and Association with SSR Markers in Soybean Germplasm

WU Bao-Duo,CHEN Hai-Feng,GUO Dan-Dan,SHA Ai-Hua,SHAN Zhi-Hui,ZHANG Xiao-Juan,YANG Zhong-Lu,QIU De-Zhen,CHEN Shui-Lian,ZHU Xiao-Ling,ZHANG Chan-Juan,ZHOU Rong,ZHOU Xin-An

Acta Agron Sin. 2012, 38(07):  1196-1204.  doi:10.3724/SP.J.1006.2012.01196

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Pod traits are important factors affecting soybean yield, and they have been identified to tightly associate with leaf shape. In present study, leaf shape/pod traits were analyzed using 167 soybean accessions, which were classified into two types (broad and narrow leaflets) based on the ratio of leaf length/width. Correlation analysis was carried out between leaf shape related traits and pod traits; ANOVA analysis was also performed using 65 SSR markers, evenly distributed in 20 linkage groups; association analysis was carried out using 13 SSR markers on the target regions. Marker 20-285, locating on chromosome I, highly associated with number of seeds per pod, indicating that the gene controlling number of seeds per pod may co-locate with marker 20-285. Almost all markers between 20-26 and 20-45 were associated with ratio of leaf length/width. We speculated that the genes controlling leaf shape were located in the region from marker 20-26 to 20-45. Hence, it was proved the target region harboring candidate genes of leaf shape and pod number was narrowed. Our study may provide a potential approach in molecular marker-assisted breeding of seeds per pod, and a theoretical guide for cloning the gene of seeds per pod.

Genetic Diversity of High-Molecular-Weight Glutenin Subunit Composition in Chinese Wheat Landraces

XU Xin,LI Xiao-Jun,ZHANG Ling-Li,LI Xiu-Quan,YANG Xin-Ming,LI Li-Hui

Acta Agron Sin. 2012, 38(07):  1205-1211.  doi:10.3724/SP.J.1006.2012.01205

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The high-molecular-weight glutenin subunit (HMW-GS) composition of 76 representative accessions of wheat landraces, collected from nine agro-ecological zones in China, were examined by sodium-dodecyl-sulphate polyacrylamide-gel electrophoresis (SDS-PAGE). The correlation between diversity indexes at Glu-1 locus and altitude, mean annual precipitation, or mean annual temperature was also analyzed. The results indicated that 19 accessions (25.0%) were heterogeneous for HMW glutenin subunit composition, and contained 2–4 HMW-GS compositions generally. At Glu-1 locus, a total of 14 different glutenin alleles were observed and the number of alleles at Glu-A1, Glu-B1, and Glu-D1 was 2, 7, and 5, respectively. Three novel alleles were identified, consisting of two alleles at Glu-B1 and one allele at Glu-D1 locus. The 14 alleles resulted in 16 different HMW subunit combinations, and the combination (null, 7+8, 2+12) was the major type with the frequency of 69.7%. The genetic diversity indexes for HMW glutenin subunits varied among agro-ecological zones, and were negatively correlated with mean annual precipitation and mean annual temperature. Environmental stress is speculated to be an important factor for the differentiation of diversity in wheat landraces across regions.

Origin and Expression of Nsa CMS Candidate Restorer Gene

ZHANG Hong,FU Li,LI Yun-Chang,LIU Jia,MEI De-Sheng,PENG Peng-Fei,CHEN Yu-Feng,HU Qiong*

Acta Agron Sin. 2012, 38(07):  1212-1220.  doi:10.3724/SP.J.1006.2012.01212

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 Nsa cytoplasmic male sterility (CMS) is a novel CMS system develpoed by somatic hybridization between Brassica napus and Sinapis arvensis. The cloning the restorer genes for Nsa CMS is important for both the development of better restorers and the mechanism understanding of fertility restoration. A candidate restorer gene named PPR618 of Nsa CMS was cloned based on the homologue sequencing strategy previously. In this study, based on sequence information of PPR618, 22 homologous sequences were identified in Nsa CMS male sterile line, Nsa CMS restorer lines, the original fusion parents which gave rise to Nsa CMS and several other B. napus lines as well as one B. oleracea and one B. rapa accessions. Sequence analysis showed that there are two PPR618 homologues in each of the fusion parental lines, S. arvensis var. Yeyou 18 and B. napus var. Zhongshuang 4, whereas there were three, one, one, and one PPR618 homologues in the four restorers, Hui 1, Hui 2, Hui 3, and Hui 4, respectively. The identity of the homologous genes in restorers was above 93% to those in Yeyou 18, but less than 80% to those in Zhongshuang 4, implicating the candidate restorer genes of Nsa CMS originated from S. arvensis. Both homologues in S. arvensis were found in the restorers, one in Hui1, Hui 3, and Hui 4, the other in Hui 2. Besides PPR618, three new candidate restoring genes were identified. The homologous genes from restorers was also found to have relations with the restoring genes for CMS system of radish and petunia. Semi-quantitative RT-PCR results showed that the candidate restoring gene expressed in all tested organs. The gene expression gradually increased along with the developmental process from vegetative to reproductive stages, peaked in the bud of 1.5–2.5 mm in diameter, and slumped in roots and stems. In contrast, the highest expression of homologous gene in male sterile line was detected in stems.

Genetic Diversity of Arachis Accessions Detected by EST-SSR from Cultivated Peanut (Arachis hypogaea L.)

TANG Mei,CHEN Yu-Ning,REN Xiao-Ping,HUANG Li,ZHOU Xiao-Jing,YAN Hai-Yan,JIANG Hui-Hang

Acta Agron Sin. 2012, 38(07):  1221-1231.  doi:10.3724/SP.J.1006.2012.01221

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The amplification efficiency and application potential for the research on peanut genetic diversity by using cultivars-derived EST-SSR primers in 89 Arachis aeecssions were assessed. Based on randomly selected 235 EST-SSR primer pairs, we detected 223 amplification bands in the 89 accessions with the amplification efficiency of 94.89%. Among them 53 primer pairs exhibited 206 polymorphic bands, which showed 1–12 bands per primer pair with an average of 3.89. The polymorphism index ranged from 0.044 to 4.040 with an average of 1.173. The average similarity coefficient was 0.685 among 89 peanut accessions, ranging from 0.442 to 0.976. The accessions from the same section were mainly clustered together, peanut cultivars were grouped into the section of Arachis, and A. duranensis had a close relation to cultivated peanut, which is coincident with botanical classification. According to the statistical analysis from the results of oil content and SSR data in wild peanuts, some interesting bands such as POCR437-180/170 were found to be potential for candidate markers related to oil content. BLAST analysis indicated that the alignment sequence of primer POCR437 corresponded to the coding genes of malonyl-CoA-ACP transacylase and acyl-carrier-protein, both of which are involved in fatty acid synthesis.

Proteomic Analysis of Bud Differentiation between Cytoplasmic Male-Sterile Line and Maintainer in Tobacco

QI Jian-Min,MA Hong-Bo,XU Jian-Tang,CHEN Mei-Xia,ZHOU Dong-Xin,WANG Tao,CHEN Shun-Hui

Acta Agron Sin. 2012, 38(07):  1232-1239.  doi:10.3724/SP.J.1006.2012.01232

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To explorethe moleculargenetic mechanismsof cytoplasmic male sterility in tobacco,we studied the differential protein between the cytoplasmic male-sterile line and its maintainer. Immobilized pH gradient two-dimensional gel electrophoresis (2-DE) technique was used to separate the protein spots while gels were stained with the Coomassie Blue G-250. The difference between protein maps of bud from cytoplasmic male-sterile line MSK326 and maintainer line K326 was analyzed with PDQuest image software. Matrix-assisted laser-adsorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) technique was used to obtain the peptide mass of differentially expressed protein spots. The Mascot software was used to search the protein database NCBInr to identify those spots interested. A total of 365 protein spots were detected within Mr 14.4–97.6 kD and pH 4–7. Seven protein spots appeared in the protein map of maintainer line K326 but absent in that of CMS line MSK326, which were identified as ribulose-1,5-bisphosphate carboxylase/oxygenase, polyphenol oxidase, patatin homolog, PSI 9 kD protein. It was inferred that the male sterility of MSK326 might be related to energy metabolism turbulence, abnormality in male organ development, deficient nutrition supply and immunity, and inhibition of energy transfer.

QTL Analysis of Rice Ratooning Ability and Related Agronomic Traits by Using RIL Populations

YANG Chuan-Hang,WANG Yu-Ping,TU Bin,LI Ting,HU Liang,LI Shi-Gui

Acta Agron Sin. 2012, 38(07):  1240-1246.  doi:10.3724/SP.J.1006.2012.01240

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A molecular linkage map containing 105 SSR marks were constructed by using a RIL population generated from the F₇ descent of a cross of japonica glutinous rice variety 89-1 and an indica heavy panicle backbone hybrid rice lines SH527. By using this map, we mapped 15 QTLs for seven agronomic traits in the normal season, which was distributed on chromosomes 1, 2, 3, 5, 6, 7, and 10, respectively. The LOD value varied from 2.10 to 7.51, and the contribution rate varied from 3.77% to 25.37%, among which seven QTLs had the contribution rate larger than 10.0%. The number of a single trait QTL varied from 1 to 5. Two QTLs (qRa4, qRa5) affecting rice ratooning ability were detected on chromosomes 4 and 5, the contribution rate was 8.17% and 7.09%, and the additive effect was 0.32 and -0.39, respectively. Thirty-six QTLs for agronomic traits were detected in two seasons and among which eight were detected repeatablely. According to the results, the ratooning ability was remarkably negatively related to the effective ear of the normal season. In addition, the ratooning ability was tightly positively related to the effective ear in the ratooning season, and was negatively related to the grain number per ear and seed density. The QTLs mapping results revealed that the effective ear of normal season and ratooning season is the main factor that affects rice’s ratooning ability.

Mapping QTL for Cell Membrane Permeability of Leaf Treated by Low Temperature in Winter Wheat

JU Wei, YANG Cai-Feng, ZHANG Shu-Hua, TIAN Ji-Chun, HAI Yan, and YANG Xue-Ju

Acta Agron Sin. 2012, 38(07):  1247-1252.  doi:10.3724/SP.J.1006.2012.01247

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To understand the genetic mechanism of cold resistance in winter wheat, we mapped quantitative trait loci (QTLs) for cellmembrane permeability of leaf treated by low temperature using compound interval method based on an existing linkage map containing 324 simple sequence repeat (SSR) markers. The map population, which was consisted of 168 double haploid lines from the cross Huapei 3 × Yumai 57, was planted in three sites, and the cellmembrane permeability of leaf treated by low temperature (−18°C) was determined with electric conductometry . A total of 21 additive QTLs associated with cell membrane permeability of leaf were detected in three environments, which were distributed on chromosomes 1B, 2A，3A, 3B, 5B, 6A, 6B, 6D, 7B, and 7D. Four loci (qCMP-1B-1, qCMP-3B-2, qCMP-5B-1, and qCMP-5B-4) with phenotypic contributions higher than 10% were regarded as major genes, and the remaining QTLs were minor genes with phenotypic contributions lower than 10%. A common locus in the Xgwm213–Xswes861.2 interval on chromosome 5B was detected in the three environments, with 0 cM genetic distance from Xswes861.2. The loci, designated qCMP-5B-1 in environment 1 and qCMP-5B-4 in environment 3, explained 17.5% and 14.0% with phenotypic variations, respectively. The result of the present study was useful for marker-assisted selection and breeding for cold resistance of wheat.

RESEARCH NOTES

Molecular Cloning and Information Analysis of ANS Genes Encoding Anthocyanin Synthases from Mulberry (Morus alba)

ZHANG Qiong-Yu, LI Jun, ZHAO Ai-Chun, WANG Xi-Ling, JIN Xiao-Yun, Li Zhen-Gang,YU Mao-De

Acta Agron Sin. 2012, 38(07):  1253-1263.  doi:10.3724/SP.J.1006.2012.01253

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Anthocyanidin synthase (ANS, leucoanthocyanidin oxygenase) is one of the critical enzymes in the biosynthesis of the anthocyanin. Anthocyanidin synthase gene fragment (designated as MaANS) was isolated from mulberry fruit (Moru alba) by RT-PCR based on homology cloning and genome walking technology. MaANS with the 5′ and 3′ was cloned by genome-walking. The full-length genomic sequence of MaANS is 1 535 bp, which consists of two exons and one intron. The coding region length was
1 077 bp, and their deduced protein consisted of 358 amino acid residues. Multiple alignments revealed that the nucleic acid of MaANS shared above 80% identity with that of Fragaria × ananassa, Ipomoea batatas, Malus domestica, and Pyrus pyrifolia. Structural analysis showed that the MaANS protein might belong to the 2 OG and Fe(II)-dependent oxygenase family. Phylogenetic tree analysis revealed that MaANS was the most close with Fragaria × ananassa, then Malus domestica and Pyrus pyrifolia. Reverse transcription-PCR (RT-PCR) analyses of MaANS transcripts showed that it was abundantly expressed in the young leaves and ripened fruit. All research made an essential foundation for pathway and regulation of gene expression in anthocyanin biosynthesis in mulberry fruit.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Relationship of Leaf Photosynthetic Characteristics and Root Physiological Traits with Grain Yield in Super Rice

FU Jing, CHEN Lu,HUANG Zuan-Hua,WANG Zhi-Qin,YANG Jian-Chang

Acta Agron Sin. 2012, 38(07):  1264-1276.  doi:10.3724/SP.J.1006.2012.01264

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The success in super rice breeding has been considered as a great progress in rice production in China. This study aimed to understand the mechanism underlying the yield formation of super rice. Four super rice cultivars, Liangyoupeijiu and IIyou 084 (indica hybrids), Huaidao 9 and Wujing 15 (japonica), and two elite check cultivars, Shanyou 63 (indica hybrids) and Yangfujing 8 (japonica), were grown in field. Leaf photosynthetic characteristics and root physiological traits were investigated at different growth stages. The results showed that average total spikelet number and grain yield of the four super rice cultivars were 43.5% and 16.1%, respectively, more than those of two elite check cultivars, but the seed-setting rate of the four super rice cultivars was low 15.3% than that of the two elite check cultivars. The contents of chlorophyll a and b, total chlorophyll (a+b) and carotenoid, photosynthetic rate, transpiration rate, stomatal conductance of leaves, and specific root oxidation activity, root oxidation activity per plant, total root absorption area per plant, root active absorption area, specific surface area were higher in super rice than in elite check cultivars at earlier growth stages, while those traits decreased more quickly in super rice cultivars than in check cultivars at latter growth stages, and lower in super rice than in check cultivars up to 20 days after full heading. The results suggest that stronger leaf photosynthetic capacity and root activity during the early and mid-growth periods contribute to greater yield sink capacity of super rice, while the rapid decline of leaf photosynthetic capacity and root physiological activity at the late growth stage results in poor grain filling, and consequently, limits yield potential of super rice. Enhancing root physiological activity at late growth stage, especially during the grain filling period would be an important approach for super rice to further increase grain yield.

Comparison of Culm Characteristics with Different Nitrogen Use Efficiencies for Rice Cultivars

LI Min1,2,ZHANG Hong-Cheng1,YANG Xiong,GE Meng-Jie,MA Qun,WEI Hai-Yan,DAI Qi-Gen,HUO Zhong-Yang,XU Ke

Acta Agron Sin. 2012, 38(07):  1277-1285.  doi:10.3724/SP.J.1006.2012.01277

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The morphological and physiological characteristics of low-yielding and low N-efficiency, high-yielding and medium N-efficiency, high-yielding and high N-efficiency of rice cultivars were investigated using six representative japonica varieties under their respective optimal N application levels. The results showed that compared with low-yielding varieties, high-yielding varieties showed shorter basal 1st internodes, longer basal 6th internodes, increased plant height, larger culm diameter and wall thickness, significantly higher dry weight of stem and sheath, obviously increased K and Si content in culm and sheath, and a higher ratio of Si to N. As a result of their improved stalk physical characteristics and the different chemical compositions, the comprehensive breaking resistance of the culm of high-yielding cultivars was improved evidently, and the lodging index reduced as well. The cultivars with different N-efficiencies displayed diverse culm morphological and physiological characteristics even though they were all in one high-yielding level. Comparing with medium N-efficiency genotypes, the high N-efficiency ones had longer 4th and 5th internode lengths, increased culm wall thickness, in spite of slightly decreased culm diameter, resulted in higher dry weight and strengthened plumpness status of culm, significantly decreased content of Si in stem and sheath, decreased N content, and remarkably unchanged K content. Given these results, for the purpose of further increasing the nitrogen fertilizer use efficiency of the high-yielding varieties, it would be favorable to properly increase 4th and 5th internode length, thus improving top three leaves configuration, to appropriately reduce the culm diameter while increasing wall thickness and filling degree for the sake of stalk breaking resistance and transporting capability, and to properly reduce the content of Si in culm and sheath to facilitate the translocation of nitrogen.

RESEARCH NOTES

Influence of Planting Density on Root Spatio-Temporal Distribution of Different Types of Maize under High-Yielding Cultivation Conditions

LI Zong-Xin,CHEN Yuan-Quan,WANG Qing-Cheng,LIU Kai-Chang,GAO Wang-Sheng,SUI Peng

Acta Agron Sin. 2012, 38(07):  1286-1294.  doi:10.3724/SP.J.1006.2012.01286

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A field experiment was conducted to compare the influence of planting density onthe root spatio-temporal distribution using two types of maize cultivar (LD981, a planophile massive ear type variety, and LD818, an erectophile middle ear type variety) under high-yielding cultivation conditions. The results indicated that the total root volume (TRV), total root-absorbing area (TRAA), active-absorbing area (AAA), and total root dry weight (TRDW) of the both maize varieties increased at first and then decreased during the growing stages. From the flowing stage to the milking stage, the above parameters reached their maximum values. The number of root layers, root number, TRV, TRAA, AAA, and TRDW decreased with the increase of planting density, but the rate of decrease in LD981 was higher than that in LD818. In the horizontal distribution, 0–6, 6–12, and 12–18 cm from the stem were classified as higher, mid, and lower root density zones, respectively; in the vertical distribution, 0–20, 20–40, 40–60, and 60–80 cm below the ground surface were classified as higher, mid, lower, and thinner root density layers, respectively. In the horizontal distribution, the percentage of root dry weight in 0–6 cm soil from the stem of LD818 was higher (2.96%) than that of LD981, but lower (14.33%) in 6–18 cm soil; in the vertical distribution, the percentage of root dry weight in 0–40 cm soil below the ground surface in LD818 was lower (3.71%) than that in LD981, but higher (14.33%) in 40–80 cm soil. The results of this study suggest that the requirement in root distribution space and orientation is different among different maize varieties. LD981 posses more roots mainly distributing in lower soil layers. LD981 is more sensitive to horizontal restriction owing to higher planting density, and suitable to be planted under lower planting density condition. LD818 shows the root distribution characteristics of “vertical extension and horizontal contraction”, adapting horizontal restriction owing to higher planting density, suitably cultivating under higher planting density condition.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Photosynthetic Characteristics and Antioxidative Metabolism of Flag Leaves in Responses to Shading during Grain Filling in Winter Wheat Cultivars with Different Spike Types

XU Cai-Long,YIN Yan-Ping,CAI Rui-Guo,WANG Ping,LI Yong,GUO Jun-Xiang,CHEN Er-Ying,ZHAI Xue-Xu,LIU Tie-Ning,WANG Zhen-Lin

Acta Agron Sin. 2012, 38(07):  1295-1306.  doi:10.3724/SP.J.1006.2012.01295

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Shading post flowering caused by cloudy weather and the surrounding protective trees often occurs in the Huang-Huai-Hai Plain of China. The objective of this study was to suggest cultivars acclimated to insufficient light intensity post flowering in this region through evaluating the impact on photosynthesis and antioxidation. Two winter wheat (Triticum aestivum L.) cultivars, Tainong 18 (a large-spike cultivar) and Jinan 17 (a multiple-spike cultivar), were treated with 100% (control, S0), 75% (S1), 50% (S2), and 10% (S3) of full radiation from anthesis to maturity. The chlorophyll content, net photosynthetic rate (P_n), contents of soluble protein and sugar, activities of antioxidative enzymes, and malondialdehyde (MDA) content were measured from 0 to 28 d post flowering. Compared to S0 treatment, the chlorophyll content and maximal efficiency of photosystem II (PSII) photochemistry (F_v/F_m) of flag leaves were enhanced in treatments S1 and S2. From 0 to 6 d post flowering, the chlorophyll content and F_v/F_m in S3 were also higher than those in S0, but significantly lower than these in controls, thereafter. With the increase of shading intensity, the effective quantum yield of PSII (Φ_PSII) was promoted; whereas, the ratio of Chl a/b was declined. Compared to S0, treatments S2 and S3 significantly suppressed the activities of superoxide dismutase (SOD) and peroxidase (POD), P_n, and contents of soluble protein and total soluble sugar, but S1 treatment showed positive effects on above parameters. Under the same shading condition, Jinan 17 had larger chlorophyll content and higher activities of PSII and antioxidative enzymes, but lower MDA content than Tainong 18. This result indicated that multiple-spike cultivar was more suitable than large-spike cultivar in the Huang-Huai-Hai Plain with shading problem at late growth period, because there were less damage of flag leaf and better photosynthetic function in multiple-spike cultivar. Wheat plants under S1 shading condition had relatively high activities of antioxidative enzymes and low degree of membrane lipid peroxidation, which was in favor of stress resistance, maintaining high P_n duration, and accumulation of photosynthate in wheat plants.

Lodging Resistance of Winter Wheat in Response to Nitrogen and Planting Density and Border Effect under Relay Intercropping Condition

FAN Gao-Qiong,LI Jin-Gang,WANG Xiu-Fang,ZHEN Ting,GUO Xiang,CHEN Yi,WU Zhong-Wei,YANG Wen-Yu

Acta Agron Sin. 2012, 38(07):  1307-1317.  doi:10.3724/SP.J.1006.2012.01307

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Southwest is the third largest wheat producing area in China, where wheat/corn relay intercropping is the typical cultivation mode. In this area, wheat is harvested in a relatively low yield due to deficiency of effective spikes. The objective of this study was to modulate spike enhancement and lodging resistance of wheat in the relay intercropping system through optimizing plant density and nitrogen application rate. Using Chuanmai 42, the major wheat cultivar in local production, a two-year field experiment was carried out in Sichuan Province from November 2009 to May 2011 under two-factor split-plot design. The main-plot was for N application rate at 120 kg ha^-1 and 180 kg ha^-1, and the sub-plot was for plant density in five levels (0.6, 1.2, 1.8, 2.4, and 3.0 million plants per hectare). The border effects on wheat population quality, stem morphology, and stem mechanical strength were investigated at different growth stages. The quantities of tillers and effective spikes in edge, second, and central lines were all enhanced with the increase of planting density; however, the biomass and its distribution proportion in spike were reduced, resulting in declined stem quality. Under the same density, border advantage was significant after jointing stage, when the edge line showed higher levels than the second and central lines in spike rate, number of effective spikes, plant dry weight, outside diameter, wall thickness of culm, internode filling degree, and mechanical strength. Plant density influenced the border effect on number of effective spikes, with the maximum effective spikes in plant density of 1.8 million plants per hectare; even higher density stimulated significant increases of the spike number in the second and central lines in company with the increased plant height and height of gravity centre, the decreased plant weight and biomass distribution proportion in spike, and the dramatically declined internode filling degree and mechanical strength, which resulted in the occurrence of early lodging and high lodging degree and lodging area percentage. Nitrogen application had positive effects on lodging index and mechanical strength of the central line, but the general effects were not significant in the two nitrogen treatments. Suggestively, plant density of 1.2–1.8 million per hectare is optimal for relay intercropping wheat in the hill area of Southwest China based on its lodging resistance and border effect on plant growth and yield formation.

Productivity Performance of High-Yield Spring Maize and Approaches to Increase Grain Yield (above 15 t ha^-1) in Irrigated Plain of Inner Mongolia

WANG Zhi-Gang,GAO Ju-Lin,ZHANG Bao-Lin,LUO Rui-Lin,YANG Heng-Shan,SUN Ji-Ying,YU Xiao-Fang,SU Zhi-Jun,HU Shu-Ping

Acta Agron Sin. 2012, 38(07):  1318-1327.  doi:10.3724/SP.J.1006.2012.01318

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It is difficult to increase grain yield (above 15 tha^-1) in irrigated plain of Inner Mongolia because of unclearness in exploring the productivity potential of high-yield spring maize colony. To solve this problem, we analyzed the yield components the yield performance parameters, and the effects of plant density on yield performance of different hybrids in split plot designs for 52 high yield maize colonies in four years,. The result showed that ear number and grain number per ear were the main factors affecting the yield of maize colony (above 15 tha^-1). The yield components of high yield colonies (above 15 t ha^-1) were as follows: 7.08×10⁴–9.60×10⁴ ears per hectare, 477–654 grains per ear, 324.7–388.7 g per 1000-grains and 168.9–234.0 g per ear. The rational indexes for high yield maize colony (above 15 t ha^-1) included the maximum LAI (leaf area index) of above 6.5, the MLAI (mean of leaf area index) of about 5.0, and the LAI at harvest stage was above 3.5. However, different hybrid cultivars demonstrated different rational yield components: cultivars with high stalk and large ear (yield over 15 tha^-1) should have 67 500–75 000 ears per hectare, 610–640 grains per ear, about 380 gram per 1000-grains, and 220–240 gram per ear; cultivars with medium or little ear on medium stalk (yield above 16.5 tha^-1) should have 75 000–97 500 ears per hectare, 520–600 grains per ear, 340–355 gram per 1000-grains, and 180–220 gram per ear. Enhancing plant density increased yield by high MCGR (mean of crop growth rate) and TGN (total grain number), but the decline in net assimilation capacity per plant resulted in remarkable reduction of GN (grain number) and thus restricted TGN potential. Adjusting population structure by increasing plant density brought about high yield above 15 tha^-1, which results from the compensation of population yield gain for individual productivity loss. Individual productivity in structure-optimized colony should be improved to break the limit of individual sink, and synchronous improvement in colony structure and individual function is the important approach to further raise yield of spring maize.

RESEARCH NOTES

Expression of Floral Meristem Identity Gene AP1 in vitro and Validation of Interaction between AP1 and FLC in Brassica juncea Coss. (Mustard)

TANG Qing-Lin,XU Jun-Qiang,SONG Ming,WANG Zhi-Min

Acta Agron Sin. 2012, 38(07):  1328-1333.  doi:10.3724/SP.J.1006.2012.01328

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There exists a possible direct interaction between floral meristem factor AP1 and flowering pathway central regulator FLC in Brassica juncea. Coss. To further prove the interactive mechanism between AP1 and FLC, the protein interaction in vitro was testified in Brassica juncea Coss. (mustard). The cDNA of AP1 gene isolated using homologous cloning techniques from mustard “QJ” was 790 bp, encoding 256 amino acids. AP1 belongs to MIKC type protein with MADS domain and K-box known from analysis software. The conserved MADS domain had two alpha helixes (a) and two beta-sheets (b), and one amino acid site in the first a helix was not conserved. The K-box had three alpha helixes (a), and one amino acid site in the first and second a helixes was not conserved, respectively, but four amino acid sites in the third a helix were not conserved. Furthermore, recombinant plasmid pET43.1a-AP1 was constructed, transformed to E. coli (BL21) and then induced protein expression by IPTG. With the characteristics of 6×His tag in fusion protein of pET43.1a-AP1 which could combine with Ni⁺, the interaction between AP1 and FLC was analyzed via SDS-PAGE. The results showed that AP1 and FLC could act with each other to combine and form a complex. This research provides theoretical and technical bases for further analyzing the interaction mechanism of AP1-FLC protein complex and the molecular regulation of floral meristem in Brassica juncea.

Developing InDel Markers from Aegilops Genus Based on Comparative Genomics

WU Lei, WANG Dan,SU Wen-Yue,GUO Chang-Hong,SHU Yong-Jun

Acta Agron Sin. 2012, 38(07):  1334-1338.  doi:10.3724/SP.J.1006.2012.01334

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The expressed sequence tags (ESTs) of Aegilops speltoides were aligned with UniGene sequences of wheat to develop molecular markers for favorable genes that can be used in wheat breeding. A total of 137 insertion/deletion (InDel) sites were identified in Ae. speltoides, and 24 pairs of primers flanking these InDel sites were designed. Of the 24 pairs of primer, 11 had polymorphic amplification in 15 species of wheat relatives, suggesting that they can be used as InDel markers. These InDel markers were functional markers involved in subcellular localization, protein binding or catalyzing, metabolic process and cell rescue, defense, and disease resistance.

Inheritance of Resistance to Powdery Mildew in 12 Wheat Cultivars

SONG Feng-Jing,XIAO Ming-Gang,HUANG Jiang,WANG Xiao-Ming,ZHU Zhen-Dong,WU Xiao-Fei,LI Hong-Jie

Acta Agron Sin. 2012, 38(07):  1339-1345.  doi:10.3724/SP.J.1006.2012.01339

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Wheat powdery mildew, caused by the biotrophic parasitic fungus Blumeria graminis (DC.) f. sp. tritici E.O. Speer. is one of the most epidemic diseases in many wheat (Triticum aestivum L.) producing regions in China and other parts of the world. The information on inheritance of resistance to powdery mildew in commercial wheat cultivars is important for controlling the disease and developing new resistant cultivars. In the present study, 17 isolates of B. graminis were used to postulate and analyze powdery mildew resistance genes in 12 wheat cultivars at seedling stage. Molecular detection was performed to disclose the presence of Pm2 and Pm8 for powdery mildew resistance. All of the 12 wheat cultivars were resistant to at least 11 tested isolates. Isolates E09, E20, and Bg2 were used to test F₂ populations for analyzing inheritance of powdery mildew resistance in these wheat cultivars. The results demonstrated that single dominant gene(s) was responsible for powdery mildew resistance in these cultivars. The reactions to different isolates of B. graminis and analysis of amplification with Pm2-linked marker Xcfd81showed that Pm2 or its allele was most likely present in Liangxing 66. Using ω-secalin gene- and Glu-B1 gene-specific markers on chromosome arms 1RS and 1BS, respectively, the presence of T1BL·1RS translocation chromosome carrying Pm8 was detected in Shannong 20 and Zhengmai 9962. Since Pm8 was not effective against most isolates tested in this study, other unknown genes for powdery mildew resistance could be present in Shannong 20 and Zhengmai 9962 in addition to Pm8. The reaction patterns of Yanzhan 4110 and Tianmin 668 were identical. The remaining cultivars developed different patterns of reaction to the B. graminis isolates tested.