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Table of Content

    13 November 2008, Volume 34 Issue 11
    • CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
      Quantitative Trait Loci for Rice Heading Time in Koshihikari
      ZHANG Yong-Sheng;JIANG Ling;LIU Xi;CHEN Liang-Ming;LIU Shi-Jia;ZHAI Hu-Qu;WAN Jian-Min
      Acta Agron Sin. 2008, 34(11):  1869-1876.  doi:10.3724/SP.J.1006.2008.01869
      Abstract ( 3800 )   PDF (368KB) ( 1487 )   Save
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      In order to verify the quantitative trait loci for rice heading time in Koshihikari, QTL mapping of heading time was studied using both Koshihikari/Kasalath BILs population and Kasalath/Koshihikari CSSLs population in Nanjing, Jiangsu province and Lingshui, Hainan province. The results indicated that three QTL of heading time were detected, which were located on chromosomes 3, 6, and 8, respectively. At qHd-3 and qHd-8 loci, the allele from Koshihikari can promote heading time for rice, but at qHd-6 loci, the allele from Koshihikari could delay heading time for rice. Epistatic interaction was detected between qHd-3 and the QTL located on chromosome 7. Comparing BILS with CSSLs linkage maps, we found that the marker regions of qHd-3, qHd-8, and qHd-7-1 coincided with Kasalath segment in W008, W023 and W024, W020, respectively. Meanwhile, QTL mapping of heading time were studied using Koshihikari/Guichao 2 RILs population, three additive QTL were detected and epistatic interaction was detected between two unadditive QTL of heading time.

      Mining Favorable Alleles of QTLs Conferring 1000-Grain Weight from Synthetic Wheat
      LIAO Xiang-Zheng;WANG Jin;ZHOU Rong-Hua;REN Zheng-Long;JIA Ji-Zeng
      Acta Agron Sin. 2008, 34(11):  1877-1884.  doi:DOI: 10.3724/SP.J.1006.2008.01877
      Abstract ( 3227 )   PDF (365KB) ( 1829 )   Save
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      In common wheat (Triticum aestivum L.), 1000-grain weight (TGW) is an important component of grain yield. However, TGW is generally negatively correlated with grain number per spike and spike number per plant and positively correlated with plant height. The aim of this study was to mine favorable alleles of QTLs conferring TGW from synthetic wheat using advanced backcross QTL analysis. A BC5F2:3 population consisting of 85 lines were generated from a cross between Laizhou 953, a Chinese commercial wheat variety, and Am3, a synthetic hexaploid wheat, followed by backcrossing with Laizhou 953 as recurrent parent and selfing. Three hundred and fourty-eight polymorphic SSR markers were used for genotyping. Using composite interval mapping (CIM), three major QTLs, QGw.caas-1A, QGw.caas-3D, and QGw.caas-4B, with alleles increasing TGW from Am3, were detected in at least two environments. They could explain phenotypic variations ranging from 10.90 to 33.79%. Among the three QTLs, the alleles originated from Am3 could increase 2.3–4.8 g of TGW without decreasing grain number or spike number, or two of them, even without increasing plant height. Using mixed-model composite interval mapping (MCIM), one QTL (QGw.caas-3D) was detected with no significant interactions across the environment. Moreover, the QTL was at the same interval as the common QTL detected in 3 environments with CIM method. It is suggested that QGw.caas-3D is insensitive to environments, and may be a stable and major QTL for TGW.

      Genetic Background and Environmental Effects on Expression of QTL for Sheath Blight Resistance in Reciprocal Introgression Lines of Rice
      XIE Xue-Wen;XU Mei-Rong;ZANG Jin-Ping;SUN Yong;ZHU Ling-Hua;XU Jian-Long;ZHOU Yong-Li;LI Zhi-Kang
      Acta Agron Sin. 2008, 34(11):  1885-1893.  doi:10.3724/SP.J.1006.2008.01885
      Abstract ( 2771 )   PDF (427KB) ( 1477 )   Save
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      Genetic background and environmental effects of QTL for sheath blight resistance to the isolate RH-9 (Rhizoctonia solani kuhn) were revealed using the reciprocal introgression line populations derived from the cross of Lemont/Teqing. Lemont is highly susceptible while Teqing resistant to RH-9. The relative lesion height (a ratio of lesion height to plant height, RLH) of TQ-ILs was normally distributed whereas that of LT-ILs was apparently inclined to the susceptible parent, Lemont. Total 10 main-effect QTLs and 13 epistatic QTLs affecting sheath blight resistance were mapped under different years and genetic backgrounds. Among them, six main-effect QTLs detected in 2006 were all verified in 2007, suggesting these QTLs had reliable performance across years. QSh4 was the only one QTL expressed under the reciprocal backgrounds and Teqing allele at this locus decreased RLH, suggesting the improvement of resistance level. QSh10a detected in the TQ-ILs and located in the region of RM216–RM311 on the chromosome 10 and QSh10b detected in the LT-ILs in the neighboring region of RM222–RM216 were not the same gene but existed tight linkage as regards to different gene directions in different backgrounds. Most QTLs identified in TQ-ILs were not expressed in LT-ILs, indicating there was evident genetic background effect. By comparative mapping, 8 QTLs detected in this study were located in the same or near regions that associated with sheath blight resistance identified in the previous studies, suggesting these main-effect QTLs could be applied in rice breeding for sheath blight resistance by marker-assisted selection. As indicated in this study, it is an effective way to further improve sheath blight resistance by selecting the QTL stably expressed in different backgrounds or pyramiding different main-effect QTLs.

      Ultrastructure in Microspore Abortion of Genic Male Sterile Line in Sesame (Sesamum indicum L.)
      YANG Xiao-Li; ZHANG Hai-Yang;GUO Wang-Zhen;ZHENG Yong-Zhan;MIAO Hong-Mei;WEI Li-Bin;ZHANG Tian-Zhen
      Acta Agron Sin. 2008, 34(11):  1894-1900.  doi:10.3724/SP.J.1006.2008.01894
      Abstract ( 2045 )   PDF (1467KB) ( 1367 )   Save
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      Sesame (Sesamum indicum L.) is an important oil-seed crop with great nutritional value, and the sesame hybrid has remarkable heterosis in many characters, especially in productivity. To investigate the abortion mechanism of genic male sterile (GMS) line in sesame, a comparative study was conducted on the fertile and sterile microsporogenesis of ms86-1 derived from the male sterile line discovered by Osman using transmission electron microscopy (TEM) techniques. According to the morphologic characteristics of the microspores, the developmental process of sesame pollen could be tentatively divided into seven stages, including microsporocyte formation stage, microsporocyte meiosis stage, tetrad stage, early microspore stage, middle microspore stage, late microspore stage, and pollen maturation stage, respectively. The abnormal phenomena observed in the sterile anthers indicated that male sterility might arise in microsporocyte formation stage. With the growth and development of the sterile anthers, the following abnormal features were observed evidently. The cell wall of the sterile microsporocytes was irregular during their formation stage. In the meiosis stage, the cell walls were getting distorted obviously, and the microsporocytes failed to form the early exine component designated as probaculums on the outside of the plasma membrane. Subsequently, abnormal villiform deposits were observed on the outside of the callose wall during the tetrad stage. As soon as the tetrad cells disintegrated, the released sterile microspores represented aberrantly dumbbell-shaped, and their exines were undergrown without any baculum. Accompanying with the delay of the degeneration process, inclusions of the tapetum cells became more abundant and few abnormal ubisch bodies were secreted. Later on, the sterile microspore was gradually crimpled as its cytoplasm agglomerated to an electron dense clot, and ultimately degraded to the complete abortion. In this paper, compared with the fertile pollen development, the abortion process and characteristics of the sterile anthers were disclosed, providing a foundation for the greater insight into the abortion mechanism of GMS line in sesame.

      Analysis of Genetic Diversity and Population Structure in Lentil (Lens culinaris Medik.) Germplasm by SSR Markers
      LIU Jin;GUAN Jian-Ping;XU Dong-Xu;ZHANG Xiao-Yan;GU Jing;ZONG Xu-Xiao
      Acta Agron Sin. 2008, 34(11):  1901-1909.  doi:10.3724/SP.J.1006.2008.01901
      Abstract ( 2132 )   PDF (471KB) ( 1714 )   Save
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      A total of 440 lentil accessions, randomly chosen from the National Gene Bank, were employed in the experiment. Fourteen polymorphic SSR markers was screened from a total of 145 SSR primer pairs, detected a total of 87 allelic variations. High level of diversity has been detected, with an average allele number of 6.2143 and an average Shannon-Weaver index (I) of 1.1869 by 14 SSR primer pairs. The results indicated significant differentiations among the 16 groups of lentil resources in genetic diversity from diversed geographic origins. The genetic diversity within alien accessions was obviously higher than that within Chinese resources. Population structure within the subcollection of 440 individuals was defined, and 8 clusters were identified based on SSR markers by using Structure 2.2 software. The results of PCA, UPGMA cluster and population structure analyses revealed that the genetic structure was multiplex; the genetic distance was broader among foreign populations than that among Chinese populations. More survey and collecting trips, conservation and study should be made for the lentil genetic resources in Shanxi, Ningxia, and Gansu provinces, where the highest genetic diversity level existed in China. Furthermore, international exchange and introduction of lentil genetic resources should be enhanced, for more systematic studies and exploitation.

      In Vitro Functional Testing of High Molecular Glutenin Subunits in Wheat
      PEI Yu-He;SUN Hui;SONG Xi-Yun;YAN Yue-Ming;JI Kang-Min;LI Qiao-Yun;HE Zhong-Hu;LIU Li;HUANG Xing-Feng
      Acta Agron Sin. 2008, 34(11):  1910-1915.  doi:10.3724/SP.J.1006.2008.01910
      Abstract ( 1804 )   PDF (739KB) ( 1404 )   Save
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      The functions of high molecular weight glutenin subunit (HMW-GS) can be analyzed by determining the parameters subject to wheat (Triticum aestivum L.) quality. However, so far, only several glutenin subunits have verified in their functions despite a lot of subunits designated. Therefore, a simple and rapid method is highly needed to detect the functions of wheat glutenin subunits. The 2 g and 10 g Mixograph have been applied in related studies in Australia and other countries. To determine the function of wheat single HMW-GS, 6 subunits, 1Ax1, 1Dx5, 1Dy10, 1Bx7, 1By8, and 1By9, were separated and purified by SDS-PAGE, and then mixed into flour of Jing 411 individually. Their effects on flour mixing properties were investigated by 10 g Mixograph testing. The tested mixing parameters were mixing time, stability time, peak resistance, peak width, right slop, and width at 8 min. Four kinds of solution were applied to obtain an appropriate control, and the solutions consisted of different combinations of 0.2% acetic acid, 50 μg mL-1 DTT, 200 μg mL-1 KIO3, and 0.1% SDS. When signal subunit was added into dough, 6 mixing parameters changed to a different degree. The effects of the 6 subunits on flour quality were ranked as 1Dy10 > 1Ax1 > 1Dx5 > 1By8 > 1Bx7 > 1By9 according to mixing time, and 1Ax1 and 1Dy10 > 1Dx5 > 1By9 > 1Bx7 > 1By8 according to stability time. The peak resistance of 1By8 was the biggest among that of all subunits. The right slop varied little among that of the 6 subunits. The width at 8 min of 1Bx7 was the smallest among that of all subunits. The 1By8 was primarily considered as a good quality subunit in this study. In addition, it is suggest that in vitro small-scale testing used in this study is an effective method to study the function of single HMW subunit.

      Genetic Diversity of Sorghum Mosaic Virus Infecting Sugarcane
      XU Dong-Lin;ZHOU Guo-Hui;SHEN Wan-Kuan;DENG Hai-Hua
      Acta Agron Sin. 2008, 34(11):  1916-1920.  doi:10.3724/SP.J.1006.2008.01916
      Abstract ( 2194 )   PDF (269KB) ( 1154 )   Save
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      In order to understand the occurrence of sorghum mosaic virus (SrMV), one of pathogenic virus causing sugarcane mosaic disease in south China, sugarcane leaf samples with mosaic symptom were collected from commercial growing fields in Guangzhou, Wengyuan, Boluo of Guangdong province and Nanning of Guangxi province. The virus was detected by one-step RT-PCR with SrMV specific primers P1 (5′-ACAGCAGAWGCAACRGCACAAGC-3′) and P2 (5′-CTCWCCGACATTCCCATCCAAGCC-3′, Y=C/T, W=T/A, K=G/T, R=A/G) based on the viral coat protein (CP) gene. The results showed that 48% samples were infected with SrMV. Ten amplified cDNA products were chosen based on host and geographic origin for direct sequencing. BLAST analysis revealed that they were all homologous to reported SrMV CP gene. To investigate the genetic diversity within the species SrMV, multiple alignment analysis of CP gene nucleotide sequences of the 10 SrMV isolates, together with all 18 SrMV isolates documented in GenBank up to date, was perfermed using Clustal W algorithm. It was showed that 28 SrMV isolates were clustered into two groups, namely hybrid sugarcane (HS) group and noble sugarcane (NS) group. The average CP gene nucleotide identities were 80% between groups, and 87% and 90% between isolates within HS and NS groups, respectively. Coincidently, most isolates in HS group were from hybrid sugarcane, whereas most isolates in NS group from noble sugarcane. This implies that SrMV has evolved under host selection. Hence, not only different pathogens and host types, but also the virus genetic diversity should be taken into consideration in sugarcane mosaic disease controlling and virus-resistance breeding.

      Cloning and Expression of BnClo1 Gene from Brassica napus
      DING Yong;CHEN Qing-Bo;XU Chun-Lei;CHANG Wei;GAN Li
      Acta Agron Sin. 2008, 34(11):  1921-1928.  doi:10.3724/SP.J.1006.2008.01921
      Abstract ( 1984 )   PDF (419KB) ( 1736 )   Save
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      Triacylglycerols (TAGs) is stored in seeds as a nutrient for germination and postgerminative growth of seedlings. TAGs storage is confined to discrete spherical organelles called oil bodies. Plant seed oil bodies comprise a matrix of TAGs surrounded by a monolayer of phospholipids embedded with abundant oleosins and some minor proteins. Three minor proteins, temporarily termed caleosin(Sop1), steroleosin(Sop2) and Sop3, have been identified in oil bodies of diverse species. With the rapid development of molecular biology, the more wide application of rape seed oil bodies on genetic engineering, the more attention to Sops 1–3. To reveal the biological function and provide scientific basis of application on plant genetic engineering for rape caleosin proteins, a gene BnClo1 encoding caleosin protein was isolated by homology-based candidate gene method combined with RT-PCR and RACE-PCR from B. nupus. The full-length cDNA clone (accession No. AY966447 in GenBank) comprised 1058 nucleotides consisting of a 36-nucleotide 5’-untranslated region, an open reading frame of 738 nucleotides, and a 284-nucleotide 3’-untranslated region. The open reading frame encoded a putative caleosin protein. The corresponding genomic sequence (1 676 nucleotides) of BnClo1 was also obtained by PCR cloning (accession no. DQ140380 in GenBank). Rapeseed genomic sequence of BnClo1 comprised six exons with five introns conservatively inserted in their coding regions. The splicing model of introns accords with the GT/AG rule in eukaryotes. In B. napus, BnClo1 was expressed in a spatially co-cordinated and temporally regulated manner. BnClo1 expression appeared to be highly regulated through embryogenesis. Northern blot demonstrated that BnClo1 mRNA was not detected in the earliest embryos, i.e. 20 DAF (day after flower) and presented in maturing rapeseeds at approximately 25 DAF. BnClo1 expression increased dramatically in the latter stages of embryogenesis, and this mRNA maintained a substantial level thereafter until the rapeseeds started to desiccate in a mode similar to oleosin mRNA. There was a single size class of BnClo1 transcript whose expression was regulated through embryogenesis. Semi-quantitative PCR showed that caleosin mRNA was only detected in the stem at two days after germination of rapeseeds. It is presumably revealed that BnClo1 is transcribed along with oleosin and steroleosin genes during seed maturation when oil bodies are actively assembled in diverse species. The deduced polypeptide of the rapeseed clone comprises 245 amino acid residues with molecular weight of 28.1 kD. Caleosin protein documented GenBank with accession no. AAY40837 might be an amphipathic protein associated with rapeseed oil bodies. Hydropathy plot and secondary structure analysis suggested that caleosin is comprised of three distinct structural domains: an N-terminal hydrophilic domain with a single Ca2+-binding EF-hand motif, a central hydrophobic anchoring domain of some 40 residues, and a C-terminal hydrophilic domain with conserved protein kinase phosphorylation sites. In addition, the central hydrophobic domain of caleosin also contained a proline-rich region with the potential to form a proline knot motif of the type that appears to be important in the lipid-body targeting. A potential amphipathic alpha helix, e.g. residues 92–114 of caleosin might play a role in their binding both of single layer membrane and lipid bodies. Caleosin protein closely integrating with lipid bodies through embryogenesis plays an important role in the biogenesis process of oil bodies. With calcium-binding, the physiological function of caleosin protein may be responsible for decomposition of oil bodies and mobilization of triglycerides during seed germination.

      Genetic Studies of Male Sterility Restorer Gene for CMS-FA Hybrid Rice
      WANG Nai-Yuan;LIANG Kang-Jing;LI Yu;WANG Ying;WANG Hong-Fei;QIU Xiu-Li
      Acta Agron Sin. 2008, 34(11):  1929-1937.  doi:10.3724/SP.J.1006.2008.01929
      Abstract ( 2026 )   PDF (324KB) ( 1263 )   Save
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      After identifying the new male sterile cytoplasm (CMS-FA) from wild rice, a series of good quality CMS-FA male sterile lines and restorer lines as well as CMS-FA hybrid rice combinations with good quality and strong heterosis were developed, based on which the genetic studies of male sterility restorer gene for CMS-FA hybrid rice was conducted. The cross of CMS-FA male sterile line Jinnong 1A × CMS-FA male sterile restorer line Jinhui 3 was made to get F1 seeds. F1 generation plants were planted and let them self-cross to get F2 seeds. In the meantime, backcrosses of male sterile line × F1 and F1 × maintainer line were carried out to get two test cross populations (male sterile line // male sterile line / restorer line and male sterile line / restorer line // maintainer line). Then the populations of P1, P2, F1, F2, B1F1, and B2F1 were planted at the same time to evaluate the three fertility indexes of stained pollen rate, bagged seed-setting percent and natural seed-setting percent, and to conduct chi-square test for the genetic segregation ratio of each population. The results showed that the F1 of CMS-FA male sterile line × CMS-FA male sterile restorer line was normal in fertility, indicating the male restorer gene (male fertile gene) is dominant genetically. F2 population had a segregation ratio of 3 fertile plants:1 sterile plant, proving that the fertility restoration of CMS-FA male sterility was controlled by a pair of dominant genes. The two populations of test cross B1F1 and B2F1 had a segregation ratio of 1 fertile plant:1 sterile plant, which proved the single gene genetic model of F2 male restorer gene (male fertile gene). The genotypes of CMS-FA three lines were temporarily determined as S(SS)for male sterile line, F(SS) for maintainer line and S(FF) for restorer line.

      Cloning and Tissue Expression of Important Enzyme Gene UGlcAE in Ramie Pectin Biosynthesis
      LIU Jian-Xin;YU Chun-Ming;TANG Shou-Wei;ZHU Ai-Guo;WANG Yan-Zhou;ZHU Si-Yuan;MA Xiong-Feng;XIONG He-Ping
      Acta Agron Sin. 2008, 34(11):  1938-1945.  doi:10.3724/SP.J.1006.2008.01938
      Abstract ( 2123 )   PDF (567KB) ( 1708 )   Save
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      Ramie [Boehmeria nivea (L.) Gaud] is one of the important fibre crops, but its deguming leads to severe environmental pollution, large energy consumption, and deteriorated fibre for spinning and so on. Pectin is one of the primary colloid matter in ramie bast, and UGlcAE gene is a key enzyme gene in biosynthesis of most polysaccharide component of pectin. To inhibit pectin biosynthesis by antisense RNA or RNAi technology, some important genes such as UGlcAE related to pectin biosynthesis must be researched firstly. In this study, the full-length sequence of UGlcAE gene was cloned successfully from ramie cultivar—Zhongzhu 1 using degenerate primer RT-PCR, RACE, and screening of full-length cDNA library. The cDNA sequence was 1 257 bp, with a 723 bp encoding region and encode 241 amino acids. The Real-time quantitative PCR analysis showed that UGlcAE mRNA accumulated abundantly most in root and UGlcAE expression in ramie tissues was root>leaf>bast>xylem. These results pave the way for regulating and controlling synthetic quantity of pectin by molecular biology method in our further research.

      Molecular Identification and Distinctness of NSa Male Sterile Cytoplasm in Brassica napus
      CHENG Ji-Hua;LI Yun-Chang;HU Qiong;MEI De-Sheng;LI Ying-De;XU Yu-Song;WANG Wei-Min
      Acta Agron Sin. 2008, 34(11):  1946-1952.  doi:10.3724/SP.J.1006.2008.01946
      Abstract ( 2076 )   PDF (516KB) ( 1250 )   Save
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      Cytoplasmic male sterility (CMS) has been widely used as an efficient pollination control system in rapeseed (Brassica napus) hybrid production. With the exploitation of wild species of Crucifer and the application of biotechnology, several cytoplasmic male sterile systems of oilseed rape have been reported in recent years. Traditional methods used for the identification of cytoplasm, however, are time and labor consuming with low efficiency. Thus, it is highly desirable to develop an efficient and accurate identification method for cytoplasm classification. Repetitive sequence based polymerase chain reaction (rep-PCR) has proved to be a good method for the identification of mitochondrial and procaryotic organisms which contain abundant repetitive sequences in genome. Fingerprints of six cytoplasmic male sterility materials including Nsa, Pol, nap, No, Ogu, and Ath were mapped using rep-PCR. Based on the PCR amplification band patterns by two primer pairs, six male sterile cytoplasms in rapeseed could be distinguished unambiguously. Two bands, ERIC750 and ERIC4000, were unique to NSa CMS which was derived from somatic hybrids between B. napus and S. arvensis. The PCR results using gene specific primers also showed that NSa is a novel cytoplasmic male sterility system in oilseed rape. Thus, a method for cytoplasm classification in oilseed rape was established. The two specific markers for NSa cytoplasm not only confirmed the distinctness of NSa cytoplasm from other male sterile cytoplasm at molecular level, but also provided useful tools for the protection of intellectual property right of this potential CMS material in rapeseed breeding and production.

      Polymorphism of Wheat TaFT Gene Expressional Sequence and the Impact to Flowering Dates
      SUN Dao-Jie;FENG Yi;WANG Hui;MIN Dong-Hong;LI Xue-Jun
      Acta Agron Sin. 2008, 34(11):  1953-1957.  doi:10.3724/SP.J.1006.2008.01953
      Abstract ( 2184 )   PDF (333KB) ( 1557 )   Save
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      It has been confirmed that the wheat vernalization gene VRN3 is an orthologue of FT. In this study, special PCR primers were designed using the software ‘DNAMAN’ based on the sequences of TaFT (GenBank No. DQ890162). The PCR products amplified from 13 cultivars with different flowering dates were sequenced from two directions. Sequence alignment was conducted using the software BioEdit. The results of DNA sequence polymorphism showed that the translational FT protein from five cultivars had mutations. The TaFT gene was mapped to chromosome 7BS using a set of nulli-tetrasomic lines and ditelosomic line 7BL of Chinese Spring. According to the vernalization characteristics and the flowering time we deduced that for the winter cultivars, the normal FT protein may accelerate flowering, the FT protein mutation will delay flowering; for the spring cultivars, the dominant vernalization allele genes may substitute the TaFT gene’s function, and FT protein variation will not obviously influence flowering dates.

      Construction of A Molecular Genetic Linkage Map of Tobacco Based on SRAP and ISSR Markers
      MA Hong-Bo;QI Jian-Min;LI Yan-Kun;LIANG Jing-Xia;WANG Tao;LAN Tao;CHEN Shun-Hui;TAO Ai-Fen;LIN Li-Hui;WU Jian-Mei
      Acta Agron Sin. 2008, 34(11):  1958-1963.  doi:10.3724/SP.J.1006.2008.01958
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      High-density genetic linkage maps are useful tools for studying genome, phylogeny and evolution, and for mapping and Cloning genes of interest. In this study, a molecular genetic map was constructed with F2 population consisting of 187 individuals from a cross of flue-cured tobacco cultivar Taiyan 7 and burley tobacco cultivar Bailei 21 by using a total of 513 SRAP primers and 42 ISSR primers. Approximately 58 out of 513 and 10 out of 42 primers, respectively, showed polymorphisms. Each of this polymorphic primers produced at least one scorable polymorphic DNA band which was visible enough for detection and scoring. The map consisted of 26 linkage groups which included 112 (92 SRAP and 10 ISSR) markers, and covered 1 560.2 cM with an average distance of 18.1 cM. Sixteen markers were still unlinked. All 26 linkage groups consisted of 2–20 markers ranging in length from 0–291.0 cM. A total of 24.1% distorted markers distributed in the map, mainly concentrated in the LG1 and LG4 linkage groups, and the others were mapped on diverse linkage groups respectively. This map will provide the basis for gene mapping and marker-assisted selection of important agronomic traits in tobacco.

      TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY
      Computer Simulation Model of the Fractional Vegetation Cover and Its Parameters Sensitivity Analysis
      QU Ying;LIU Su-Hong;XIE Yun
      Acta Agron Sin. 2008, 34(11):  1964-1969.  doi:10.3724/SP.J.1006.2008.01964
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      Fractional Vegetation Cover (FVC) is an important ecology parameter, which is essential in the studies of hydrology, ecology and global variation. The results of the estimation methods used at present for FVC, including eyeballing method and digital camera imagery interpretation method, are obviously subjective and uncertain. Furthermore, it is rather difficult for the statistical relationship between FVC and leaf area index (LAI) to establish by measurement of millions of samples that have similar vegetation structure parameters. So it is an effective way for the estimation of FVC to develop a statistical model between FVC and LAI. In the paper, we took soybean for example, simulated the soybean leaves by using ellipses, and determined the position, orientation and size with random distribution function by choosing the key parameters in the soybean structure to obtain the FVC per area under different vegetation structure parameters. The model was validated by data measured in situ and the theoretical conclusion. The parameter sensitivity of the simulation model was analyzed, the result showed that (1) the length of stem is not a sensitive parameter when it is longer than foliage interval while the angle of stem is not a sensitive parameter until it reaches a threshold; (2) leaf tilt angle and foliage interval is in inverse portion to the fractional vegetation cover while the semimajor and semiminor axis of leaf is in direct portion to the fractional vegetation cover; (3) semiminor axis of leaf is a much more sensitive parameter than semimajor axis of leaf. It suggested that it was a novel and feasible way for FVC.

      Effects of Exogenous Ca2+ on Somatal Movement and Plasma Membrane K+ Channels of Vicia Guard Cell under Salt Stress
      ZHAO Xiang;WANG Yan-Liang;WANG Ya-Jing;WANG Xi-Li;ZHANG Xiao
      Acta Agron Sin. 2008, 34(11):  1970-1976.  doi:10.3724/SP.J.1006.2008.01970
      Abstract ( 2496 )   PDF (372KB) ( 1723 )   Save
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      Soil salinity is a key abiotic stress in crop production worldwide, especially in countries where irrigation is an essential aid to agriculture. Salt stress disturbs intracellular ion homeostasis of plants, which leads to membrane dysfunction, attenuation of metabolic activity, and secondary effects causing growth inhibition and ultimately death. Salt tolerance in plants is the ultimate manifestation of several physiologic processes, including ion uptake and membrane flux, ionic balance and distribution. Previous researches have shown that K+ inward rectifying channels, outward rectifying channels, high affinity K+ transporter (HKT) and low affinity cation transporter (LCT) may facilitate Na+ influx under NaCl stress. Extracellular free Ca2+ concentration ([Ca2+]ext) enhances salt tolerance and salinity stress elicits a transient increase in cytosolic free Ca2+ concentration ([Ca2+]cyt). The transient increase in [Ca2+]cyt activates the PP2B phosphatase calcineurin leading to the transcription of ENA1, which encodes the P-type ATPase that is primarily responsible for Na+ efflux across the plasma membrane or activates the SOS signal pathway which negatively controls this Na+ influx system. At the plasma membrane, high cytosolic Ca2+ levels can cause activation of anion channels and reduce the conductivity of inward K+ channels , thus reducing water loss. To better understand Ca2+ function in K+ and Na+ uptake, here, we investigated the effect of calcium on stomatal movement and K+ channels of Vicia faba under NaCl stress. The results showed that 100 mmol L-1 NaCl significantly induced stomatal opening, CaCl2 facilitated NaCl-induced stomatal opening at concentration of 0.1 mmol L-1 and significantly inhibited NaCl-induced stomatal opening at concentration of 10 mmol L-1. To gain further insights into Ca2+ function in NaCl-regulated stomatal movement, Vicia faba guard cell protoplasts were patch-clamped in a whole-cell configuration and the results showed that Ca2+ significantly inhibited inward rectifying and outward rectifying K+ current when NaCl and CaCl2 were added to the bath solution together, at concentration of 100 mmol L-1 and 10 mmol L-1 respectively, which was alleviated by LaCl3 at concentration of 1 mmol L-1. In contrast, 10 mmol L-1 CaCl2 alone significantly inhibited inward rectifying K+ current and activated outward rectifying K+ current, which was not alleviated by LaCl3. A single-cell analysis of cytosolic H2O2 using 2’,7’-dichlorofluorescin (H2DCF-DA) revealed that Ca2+ can induce the generating of H2O2 in the guard cells with 10 mmol L-1 CaCl2 under 100 mmol L-1 NaCl stress, but 10 mmol L-1 CaCl2 or 100 mmol L-1 NaCl had little effect on the accumulation of H2O2 in the guard cells, respectively. These results suggest that calcium may alleviate the damage caused by NaCl stress through inducing the production of H2O2,in turn the H2O2-activated increases in [Ca2+]cyt in guard cells decrease Na+ uptake by the regulation of plasma membrane K+ channels in guard cells leading to stomatal closure and reduction of water loss. These findings open new perspectives about Ca2+-based signaling in responsive to salt stress in plants.

      Characteristics of Starch Synthesis in Grains and Translocation of Carbohydrate in Leaves and Sheaths at Filling Stage for Low Phytic Acid Mutant Rice
      ZHAO Ning-Chun;WEI Ke-Su;WU Dian-Xing;ZHANG Qi-Fang;CHENG Fang-Min
      Acta Agron Sin. 2008, 34(11):  1977-1984.  doi:10.3724/SP.J.1006.2008.01977
      Abstract ( 2073 )   PDF (477KB) ( 1406 )   Save
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      For the purpose of recognizing the physiological effects of phytic acid (PA) on rice plumpness and grain weight, rice cultivar XQZ and its low PA mutant (os-lpa1) were applied to compare the difference in the changing patterns of PA, sucrose content and starch accumulation at filling stage, translocation of carbohydrates in different organs (flag leaf, culm, and sheath) and the activities of some key enzymes involved in grain starch synthesis metabolism. The results showed that os-lpa1 had higher contents of sucrose and total soluble sugar, and more starch accumulation in the flag leaf, culm and sheath, but lower starch synthesis in grains at filling stage compared to XQZ. The relatively lower activities of ADPG-Ppase and SPase in filling grains were probably responsible for poor plumpness and low starch accumulation in os-lpa1. Additionally, compared with XQZ, os-lpa1 exhibited lower activities of SPS and FBPase in sheath at filling stage, resulting in excessive accumulation of starch and blocked flows of assimilates, which could be one of the reasons for the descending yield of os-lpa1.

      Analysis of Matter Production Characteristics under Different Nitrogen Application Patterns of Japonica Super Rice in North China
      SHI Hong-Ru;ZHANG Wen-Zhong;XIE Wen-Xiao;YANG Qing;ZHANG Zhen-Yu;HAN Ya-Dong;XU Zheng-Jin;CHEN Wen-Fu
      Acta Agron Sin. 2008, 34(11):  1985-1993.  doi:10.3724/SP.J.1006.2008.01985
      Abstract ( 1969 )   PDF (240KB) ( 1147 )   Save
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      The japonica super rice in North China ‘Shennong 265’ was used to study the tiller dynamics, the LAI dynamics, matter production characteristics, yield component characteristics and the effects of matter production characteristics on yield under four different nitrogen application patterns. The results showed that for each nitrogen application pattern, the yield under high nitrogen application (14.5 kg 667 m-2) was significantly higher than that under low nitrogen level (12.5 kg 667 m-2). On yield component, the high yields under high nitrogen application patterns lay in the increase of factors “outside panicles” (number of panicles, number of spikelet per square meter, filled grains per square meter) and the decrease of factors “inside panicles” (weight per panicle, 1 000-grain weight, seed setting rate, total number of grains per panicle, number of filled grains per panicle). On the same nitrogen application level, the yields of “Five-time application in three periods” (FTATP) pattern and “Stable application at early stage large application at middle stage and satisfied application at late stage” (SELMSL) pattern were significantly higher than those of “All application at early stage” (AAES) pattern and “Slow-release fertilizer applied once at early stage” (SRFAOES) pattern. But the yield components of FTATP and SELMSL were different. FTATP increased yield by improving factors “outside panicles”, while SELMSL reached high yield by improving factors “inside panicles”, The yields of FTATP and SELMSL were significantly higher than those of AAES and SRFAOES, which lay in the increase new assimilate after heading (assimilate supplying directly) and the secondary utilization of the matter accumulated in nutritorium before heading (assimilate supplying indirectly) under FTATP and SELMSL. And the matter output rate and contribution rate to the yield from nutritorium were higher than those under AAES and SRFAOES. Besides, with the two nitrogen application levels, FTATP and SELMSL had significantly higher Agronomic N use efficiency, Apparent N recovery efficiency, total N per square meter than the other patterns. Under 14.5 kg 667 m-2 of nitrogen application, FTATP and SELMSL reached the super high yield (>11 t ha-1).

      Effect of Broadcasting Rice Seedlings in the Field with High Standing-Stubbles under No-tillage Condition on Yield and Some Physiological Characteristics
      REN Wan-Jun;LIU Dai-Yin;WU Ju-Xian;YANG Wen-Yu;FAN Gao-Qiong
      Acta Agron Sin. 2008, 34(11):  1994-2002.  doi:10.3724/SP.J.1006.2008.01994
      Abstract ( 2147 )   PDF (327KB) ( 1172 )   Save
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      In comparison with conventional tillage and transplanting (CTT) and conventional tillage and broadcasting seedlings (CTB), the trend of tillering, growth of roots, characteristics of grain filling and yield for broadcasting seedlings in the field with high standing-stubbles under no-tillage condition (BSNT) were analyzed. Meanwhile, the effects of seedling raising methods and seedling age on the yield and yield components were studied. The results showed that, for BSNT, the speed of tillering was slow, the effective panicles were less than those for CTT and CTB, 10 d after heading, the root growth ability was higher than that for CTT and CTB in BSNT. At 30 d after heading, intensity of root bleaching sap was significantly stronger in BSNT than in CTT and CTB, at late stage, the senescence of BSNT plant was deferred. According to the Richards equation, little difference of superior grains at filling stage was found among three tillage and cultivation methods, but for BSNT, the grain-filling time (t99) of inferior grains was prolonged, the weight of inferior grains was raised, spikelets of per ear, seed-setting rate, and 1 000-grains weight were increased. There was little difference of yield among three tillage and cultivation methods. Under the condition of no-tillage and returning straw to soil with high standing-stubbles, the broadcasted seedlings with soil around roots and raising on dry land beds had more roots and higher root vigor, hastened the growth of tillers, it’s yield was significantly higher than that raising on plastic trays. Among three treatments of broadseedling age, the yield in the treatment of 40 d was the highest.

      Effect of Shading on the Photosynthetic Characteristics and Yield at Later Growth Stage of Hybrid Rice Combination
      ZHU Ping;YANG Shi-Min;MA Jun;LI Shu-Xing;CHEN Yu
      Acta Agron Sin. 2008, 34(11):  2003-2009.  doi:10.3724/SP.J.1006.2008.02003
      Abstract ( 2124 )   PDF (343KB) ( 1534 )   Save
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      Photosynthetic characteristics in shading treatment and adaptation mechanism under adverse conditions were studied using in six hybrid rice combinations with different photosensitivity. The results showed that the grain yield was significantly reduced under shading treatment (80% shading rate) at heading stage, then recovered to natural illumination; the chlorophyll (a+b) and chlorophyll b contents were increased, but failed to reach the normal level after the recovery period; low light reduced the photosynthetic rate of the functional leaves and the quantity of photosynthetic products transported to grain, meanwhile, the content of malondialdehyde (MDA) and leaf area index were increased, the activity of SOD varied differently. There was a great difference in adaptability to low light environment among combinations. It is the physiological basis of rice tolerance to shading that the flag leaf under low light stress can maintain a higher net photosynthetic rate (Pn), quantum efficiency, chlorophyll content, and lower content of malondialdehyde (MDA) and lower SOD activity.

      Dynamics of Drought Resistance Based on Drought Stress Coefficient Derived from Plant Height in Wheat Development
      WU Xian-Shan;WANG Zheng-Hang;CHANG Xiao-Ping;JING Rui-Lian
      Acta Agron Sin. 2008, 34(11):  2010-2018.  doi:10.3724/SP.J.1006.2008.02010
      Abstract ( 2150 )   PDF (171KB) ( 1190 )   Save
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      Plant height is a crucial agronomic trait for grain yield in wheat (Triticum aestivum L.). To detect changes of drought resistance in wheat development, drought stress coefficient (DS|WW) was calculated in five environments (year &#61620; experimental site) based on plant heights of 150 doubled haploid (DH) lines derived from Hanxuan 10× Lumai 14 at five measuring stages using conditional analysis method. The plant heights were measured every 7 d from jointing to flowering (S1–S5) in both rain-fed (drought stress, DS) and well-watered (WW) conditions in five environments including Fenyang, Shanxi in 2001 (F01), Haidian, Beijing in 2005 (H05) and 2006 (H06), Changping, Beijing in 2005 (Ch05) and 2006 (Ch06). DS|WW is the special responding of plant height to DS condition relative to WW condition. Unconditional drought stress coefficient (UDS|UWW) represents drought resistance before time t, and conditional drought stress coefficient (CDS|CWW) represents drought resistance within the period from time(t-1) to t. In all five environments, the plant heights were significantly lower under DS than under WW at all five stages (P<0.005). The largest plant height difference between under DS and under WW appeared in F01. The differences among environments for both UDS|UWW and CDS|CWW at each developmental stage were significant at P<0.0001. However, the result from multiple comparison analysis showed that part differences between environments in the same experimental site or year after S2 were insignificant, such as UDS3|UWW3 between H06 and Ch06, UDS5|UWW5 between H05 and H06. The significant positive correlations were detected for UDS|UWW between stages except five of ten correlation coefficients in Ch05. Poor correlations were observed for CDS|CWW between stages, however, the correlations between the adjacent stages appeared closer. In all environments, the significant positive correlations were always detected between UDS|UWW at time t and CDS|CWW before time t in one or more periods, indicating that the drought resistance at time t might partially attribute to that before time t. Path analysis suggested that drought resistance before jointing stage (CDS1|CWW1) and from heading to flowering (CDS5|CWW5) might play important roles for plant height at maturity, so, an ample supply of water at these periods are helpful for gaining higher yield.

      Physiological and Biochemical Characteristics of Dongnongdongmai 1 before Wintering in High-Cold Area
      YU Jing;ZHANG Lin;CUI Hong;ZHANG Yong-Xia;CANG Jing;HAO Zai-Bin;LI Zhuo-Fu
      Acta Agron Sin. 2008, 34(11):  2019-2025.  doi:10.3724/SP.J.1006.2008.02019
      Abstract ( 2387 )   PDF (246KB) ( 1507 )   Save
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      Developing crop cold-resistance is an important breeding target in cold areas. Although simulated experiments have been conducted in house for selecting cold-resistant varieties, it is not clear the performances of varieties in the field, especially the step-by-step cold exercise in simulated experiments is hardly consistent with that in natural condition. Dongnongdongmai 1 is winter wheat (Triticum aestivum L.) cultivar that can bear low temperature and grow normally in Heilongjiang Province. To provide basic data for cold-resistant breeding and cultivation in wheat, several physiological and biochemical characteristics related to cold resistance were compared using Dongnongdongmai 1 (winter greening rate more than 85% in spring) and Jimai 22 (cold sensitive, winter greening rate less than 1% in spring). Both cultivars were planted in field condition and sampled at different dates (different temperatures) before wintering. The samples were separated into leaves, tillering nodes, and roots, respectively. The results showed that soluble sugars, soluble protein, proline, chlorophyll content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity of Dongnongdongmai 1 were higher than those of Jimai 22. Water contents in different organs and relative electric conductivity of Dongnongdongmai 1 were lower than those of Jimai 22, indicating Dongnongdongmai 1 had higher adaptability to coldness than Jimai 22. Tillering node was the most important organ for safely wintering because it contained more substances related to cold-resistance than leaf and root.

      Screening Marker Varieties with Drought Resistance in Cultivated Rice (Oryza sativa L.) Using Identification Method with Soil Moisture Gradient
      ZHANG An-Ning;WANG Fei-Ming;YU Xin-Qiao;MEI Han-Wei;LUO Li-Jun
      Acta Agron Sin. 2008, 34(11):  2026-2032.  doi:10.3724/SP.J.1006.2008.02026
      Abstract ( 2028 )   PDF (223KB) ( 1456 )   Save
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      Twenty rice varieties with different drought resistance (DR) in the field were selected to be revaluated on the DR degree using the identification method with soil moisture gradient. After 24 days drought stress treatment, the soil water contents in normal irrigation and drought stress treatments were 42.0% and 7.9%, respectively. The results showed that both normal irrigation and drought stress treatments in the same field were achieved at the same time. These varieties were classified into five groups based on drought index. According to drought index and major agronomic performance, five “marker variety” were selected: IR55459-05 (high resistance), MARAVILHA (resistance), MONOLAYA (medium resistance), IR30358-084-1-1 (medium susceptible) and IR7790-18-1-2 (susceptible). The marker varieties and the standard DR screening process can be used as a reference rice drought resistance studies and breeding in the future.

      Characteristics of Nutrient Assimilation and Dry Matter Accumulation of Bt Cotton (Gossypium hirsutum L.) in Coastal Saline Soil
      XIN Cheng-Song;DONG He-Zhong;TANG Wei;ZHANG Dong-Mei;LUO Zhen;LI Wei-Jiang
      Acta Agron Sin. 2008, 34(11):  2033-2040.  doi:10.3724/SP.J.1006.2008.02033
      Abstract ( 1972 )   PDF (184KB) ( 1081 )   Save
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      The deficiency and disequilibrium of nutrient in coastal saline soil seriously hinder growth and development of cotton. It is urgent and necessary to study on changes of nutrient assimilation, nutrient use efficiency and dry matter accumulation of Bt cotton by measuring nutrient content and dry matter weight of different plant organs. And it can provide an important basis and guidance for economic application on fertilizers and nutrition improvement of Bt cotton in coastal saline soil. The experiments were conducted with two Bt cotton cultivars, spring cotton SCRC18 and short-season cotton SCRC19, in three types of coastal saline fields, high-, middle- and low-yield, in Yellow River Delta, Shandong province. The nutrient (N, P and K) assimilation, net photosynthetic rate (Pn) and dry matter accumulation characteristics were investigated. The results showed that main nutrient uptake of Bt cotton in middle- and low-yield fields was significantly lower than that in high-yield field. But nutrient use efficiency in physiology (NUEp) in middle- and low-yield fields was significantly higher than that in high-yield field. Average NUEp of Bt cotton in high-, middle- and low-yield fields was 4.81, 6.33, and 8.05 kg Lint kg-1 N, 28.57, 40.06, and 50.48 kg Lint kg-1 P, and 9.16, 11.58, and 12.76 kg Lint kg-1 K, respectively. Generally, N was higher than K, and much higher than P in nutrient uptake ratio. Pn and biomass yield of Bt cotton in middle- and low-yield fields were obviously lower than those in high-yield field. And lint yield in middle- and low-yield fields was by 12.44% and 36.93% lower, respectively, than that in high-yield field. However, the ratio of seed cotton to straw in middle- and low-yield fields was significantly higher than that in high-yield field. Further analysis indicated, there were high salt content, and poor availability and supply capacity of nutrient in middle- and low-yield fields in coastal saline soil. These factors inhibited the nutrient assimilation and photosynthesis, and hindered growth and dry matter accumulation of Bt cotton. It was recommended that low- and middle-yield fields should have precedence over high-yield field in fertilization. It was also suggested that more P and K fertilizers should be applied in high-yield field, while more N and P fertilizers should be applied in low-yield field, according to characteristics of nutrient assimilation of Bt cotton and soil fertility in coastal saline soil.

      RESEARCH NOTES
      Evolution Characteristics of Agronomic Traits in Cultivar Replacement of Early Season Indica Rice
      YUAN Jiang; WANG Dan-Ying;LIAO Xi-Yuan;DING Yan-Feng;SHAO Guo-Sheng;XU Chun-Mei;PENG Jian;WANG Shao-Hua;ZHANG Xiu-Fu
      Acta Agron Sin. 2008, 34(11):  2041-2045.  doi:10.3724/SP.J.1006.2008.02041
      Abstract ( 1853 )   PDF (283KB) ( 1255 )   Save
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      Eighteen leading cultivars released from 1934 to 2006 and widely planted ever in south China were used, and classified into four rice genotypes, i.e. high-stalk cultivar (HC), dwarf cultivar (DC), dwarf and resistant cultivar (DRC), high-quality and super cultivar (QSC) in the present study conducted at 2006 and 2007 under conventional cultivation conditions. Plant height and growth duration as typical agronomical traits and grains per panicle, effective panicles and 1000-grain weight as main yield parameters were investigated in the study. Results showed that grain yield was increased with the increase of harvest index, grains per panicle and grain density in the evolution of the cultivars. The results further indicated that higher grains per panicle were closely related to the higher grain density. The regression analysis results showed that plant height and biomass tended to increase after 1980, while growth duration decreased. The correlation analysis showed that there were four key factors, biomass, plant height, harvest index, and grains per panicle, affecting grain yield.

      Relationship between Fraction of Photosynthetically Active Radiation and Vegetation Indices, Leaf Area Index of Corn and Soybean
      YANG Fei; ZHANG Bai;SONG Kai-Shan;WANG Zong-Ming;LIU Huan-Jun;DU Jia
      Acta Agron Sin. 2008, 34(11):  2046-2052.  doi:10.3724/SP.J.1006.2008.02046
      Abstract ( 2452 )   PDF (265KB) ( 2429 )   Save
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      Based on the measured reflectance, photosynthetically active radiation, and leaf area index (LAI), nine common vegetation indices and two vegetation indices, developed by the authors according to the characteristic of reflectance curves and the vegetation index structures, were used to estimate fraction of photosynthetically active radiation (FPAR) in corn (Zea mays L.) and soybean [Glycine max (L.) Merri.]. The relationships between vegetation indices and FPAR differed in different vegetation types. The performances of of near infrared and shortwave bands were better than these of visible and near infrared bands in FPAR estimatin by vegetation indices. Normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) were the best in the vegetation indices calculated by reflectance in visible and near infrared bands for FPAR estimation, with R2 of estimating models 0.82 and 0.81 for corn, both of 0.81 for soybean. Normalized difference shortwave index (NDSI) and ratio shortwave index (RSI) were best in the vegetation indices calculated by near infrared and shortwave bands with almost the same R2 values for NDSI and RSI in corn (0.86) and soybean (0.84). It is suggested that the near infrared and shortwave bands are feasible to be used for FPAR estimation. According to the field experiments, the water content of vegetation canopy had larger effect on FPAR estimation than soil background. The canopy FPAR and LAI showed good logarithm relations in corn and soybean canopy with R2 values of 0.75 and 0.70, respectively, indicating that vegetation indices are better than LAI for FPAR estimation.

      Differentiation of Leaf Primordium in Maize Regulated by Exogenous Cytokinin
      MA Qing;QI Lu-Lu;LI Xiao-Yu;XIANG Yan;ZHU Su-Wen;CHENG Bei-Jiu
      Acta Agron Sin. 2008, 34(11):  2053-2058.  doi:10.3724/SP.J.1006.2008.02053
      Abstract ( 2572 )   PDF (242KB) ( 1343 )   Save
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      The 12-day immature embryos of 2 maize (Zea mays L.) inbred lines with alternative phyllotaxy, 8701d and H4d, were cultured on media with different contents of 6-BA for 14 d to produce calluses, which were further subcultured twice on the same media. Type II calli were established on the differentiation mediums with 0–3 mg L-1 of 6-BA content ladder to induce sprout formation. Sprouts in shoot tips were peeled off under a dissecting microscope and the images of the phyllotactic patterns of leaf primordium were taken by scanning electron microscope. The contents of 6-benzylaminopurine (6-BA), zeatin riboside group (ZRs), dehydro zeatin riboside group (DHZRs), isopentenyladenosine group (iPAs), napthalene acetic acid (NAA), and indole-3-acetic acid (IAA) in shoot apical meristem were measured by ELISA method. Three phyllotactic patterns, namely opposite, misshapen, and alternate were observed in the leaf primordium. In H4d plants, exogenous application of the cytokinin 6-BA induced a change in the phyllotaxy of shoot apical meristem (SAM) from alternate to opposite and misshapen. Higher 6-BA content and earlier treatment led to higher proportions of SAM with misshapen leaf primordia and opposite leaf primordia. The cytokinin/auxin (CTK/AUX) ratio in SAM with misshapen leaf primordia was higher than that with decussate leaf primordia, which in turn, was higher than that with alternate leaf primordia. The accumulation of cytokinin 6-BA increased the levels of cytokinin in SAM, but did not change the levels of endogenous cytokinins (ZRs, DHZRs, and iPAs). The comeback of CTK/AUX ratio in tissue cultured immature seedlings could induce the leaf primordium of them to come back to the original phyllotactic patterns. The CTK/AUX ratio is the determinative factor that regulates the differentiation of maize leaf primordium.

Co-sponsored:
the Crop Science Society of China
the Institute of Crop Science, CAAS
China Science Publishing & Media Ltd.
Published: Science Press
Editor-in-chief: Wan Jian-min
Associate Editors-in-Chief:
Chen Xiao-ya Yang Jian-chang Zhang Xian-long Wang Jian-kang Xu Ming-liang Liu Chun-ming Wang Dao-wen Sun Chuan-qing Ding Yan-feng Jin Wei-wei Chu Cheng-cai Cheng Wei-hong
Director of the editorial department:
Yan Chun-ling
CN 11-1809/S
ISSN 0496-3490
Post subscription code: 82-336

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  • Started in 2013
  • Covered by SCIE
  • Open access in ScienceDirect

Editor in chief: Wan Jian-min
CN 10-1112/S
ISSN 2095-5421, 2214-5141(online)
Online published:
https://www.sciencedirect.com/journal/the-crop-journal
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E-mail: cropjournal@caas.cn
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