Table of Content

12 October 2008, Volume 34 Issue 10

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Analysis on Bacterial Blight Resistance of Xa23-Transgenic Rice

ZHANG Xiao-Hong;WANG Chun-Lian;LI Gui-Fen;ZHANG Xiao-Ke;LIANG Yun-Tao;SUN Liang-Qing;ZHAO Kai-Jun

Acta Agron Sin. 2008, 34(10):  1679-1687.  doi:10.3724/SP.J.1006.2008.01679

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Transgenic rice plants were previously generated by Agrobacterium-mediated transformation during our research on molecular cloning of Xa23 gene, a bacterial blight (BB) resistance gene from the wild rice species Oryza rufipogon. To investigate the stability and inheritance of the transgene and its corresponding BB-resistance phenotype, more than 350 Xa23-trangenic rice plants from T₀, T₁, and T₂ generations were subjected to BB-pathogen inoculation, PCR and Southern blot analysis for the trans-gene. Results showed that, Xa23 gene was incorporated and expressed in the genome of the susceptible receptor rice variety Mu-danjiang 8 that acquired BB-resistance. Due to the difference of the transgene insertion sites, T₀ plants with single-copy insertion performed quite different degrees of resistance and their resistance was accurately and stably inherited to T₁ and T₂ generations. We also observed that the transgene in the single-copy insertion transgenic lines inherited following the Mendelian rules. Two homozygous, single-copy insertion transgenic lines with different resistance degrees have been obtained.

Isolation and Identification of a GmGβ1 Interacting Protein with GmDREB5 Protein in Soybean (Glycine max)

YU Yue-Hua;CHEN Ming;LI Lian-Cheng;XU Zhao-Shi;LIU Yang-Na;QU Yan-Ying;CAO Xin-You;MA You-Zhi

Acta Agron Sin. 2008, 34(10):  1688-1695.  doi:10.3724/SP.J.1006.2008.01688

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It is well know that the DREB (dehydration responsive element binding protein) transcription factors in the AP2/ERF family play important roles in the regulation of plant stress responses, hormone responses and so on. GmDREB5, a novel DREB homologous gene, was isolated from soybean (Glycine max) and transferred into tobacco in our previous study. To investigate its function, the T₂ transgenic tobacco plants with GmDREB5 and the wild type plants were inoculated on MS medium with 100 mmol L^-1 NaCl and 2% PEG, and their phenotypes were observed 40 days later. The results showed that the growth of the transgenic plants was more vigorous, and their roots were longer on the medium containing 2% PEG than those of wild type plants. The germination rate of transgenic plants (75%) was five-fold higher than that of the wild type plants (15%) on the medium containing NaCl, indicating that the over-expression of GmDREB5 improved the tolerances to both drought and salt stresses. The interacting proteins of GmDREB5 was attained by screening the cDNA library of soybean under drought and identified by yeast-two-hybrid system. It was found that there existed conservative domain WD40 in the interacting proteins,and which shared 61% and 52% similarity of the amino acid sequence with G protein β subunit in cotton (Gossypium hirsutum) and rice (Oryza sativa), respectively, The interacting protein with GmDREB5, named GmGβ1, was isolated and proven to be a G protein β subunit in soybean. The prey vector containing GmGβ1 and bait vector pGBKT7-IIR were co-transformed into yeast AH109, then incubated on mediums with shortage of four components (SD/ trp- leu- his- ade-) for 3–5 days, and the results showed that the thansformants but the contorol grew normally ,and could activate the expression of the downstream reporter gene LacZ, which performed interaction between GmDREB5 and GmGβ1. Further analyses showed that the expression of GmGβ1 gene in soybean was induced by drought, high salt, cold stresses and ABA treatment. These results suggested that GmGβ1 might involve in not only response to abiotic stress but also regulation of GmDREB5 by interacting in soybean.

Locating QTLs for Plant Water Status under Drought Condition in Over-lapping Introgression Lines of Rice (Oryza sativa L.)

ZHAO Xiu-Qin;XU Jian-Long;ZHU Ling-Hua;LI Zhi-Kang

Acta Agron Sin. 2008, 34(10):  1696-1703.  doi:10.3724/SP.J.1006.2008.01696

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Drought tolerance (DT) is becoming one of the most important target traits in rice variety improvement under ever-increasing severe drought situation all over the world and identifying genomic regions contributing to DT will help to develop cultivars suitable to drought environments. The maintenance of higher plant water status are known to contribute to increase yield and yield stability under drought in cereals. In present study, the relationship between the traits related to plant water status and grain yield (GY) was analyzed and the quantitative trait loci (QTLs) linked to target traits were mapped by means of 55 introgression lines (ILs) selected from 254 advanced backcross introgression population derived from Lemont/Teqing in the Teqing background. The ILs and parents were planted in PVC pipes in screen house and phenotyped under drought and/or irrigation conditions. Significant phenotypic correlation between GY and the traits related to plant water status was observed. QTLs related to plant water status were identified which included seven for relative water content (RWC), seven for leaf water potential (LWP), five for osmotic potential (Y) and five for leaf rolling (LR) under drought condition, moreover, five QTLs for grain yield (GY) and five QTLs for biomass (BM) were detected under both drought and control conditions. By comparing the coincidence of QTLs with specific traits, we genetically dissected the nature of association among different traits related to plant water status and the association between GY and plant water status under drought. This study demonstrated that the region RM509–RM163 on chromosome 5 identified for plant water status-related DT component QTLs also had pleiotropic effects on yield under stress and control conditions. Moreover, the eleven QTLs, QLr5, QRwc5, QY5, QLr2, QLr7, QLr8, QLr9, QRwc3, QRwc4a, QRwc12, and QY7 controlling the same traits were detected in different genetic populations which means these regions were relatively stable to the environment or/and genetic backgrounds. The consistent QTLs for plant water status under stress might be useful for marker as-sisted selection (MAS) breeding in rice for DT improvement.

Resistance Identification and Genetic Diversity among Soybean Cultivars Based on Resistance Gene Analogue

SUN Shi;ZHAO Jin-Ming;WU Xiao-Ling;GUO Na;WANG Yuan-Chao;TANG Qing-Hua;GAI Jun-Yi;XING Han

Acta Agron Sin. 2008, 34(10):  1704-1711.  doi:10.3724/SP.J.1006.2008.01704

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Phytophthora root rot caused by Phytophthora sojae is a destructive disease for soybean [Glycine max (L.) Merr.] in soybean production regions of the world. Utilization of resistant varieties is the most economical and environmentally safe method for controlling this disease. A total of 48 soybean cultivars, which mainly used in Huang-Huai Valley, were analyzed to study their resistance to P. sojae by identifying seedlings with 7 stains of P. sojae. The resistance to P. sojae varied among different cultivars, which were divided into 8 groups at 0.682 similarity coefficient. The results showed that there exist the rich resistant soybean resources to P. sojae in Huang-Huai Valley. Most known plant disease-resistance (R) genes include nucleotide binding site (NBS) or leucine-rich repeats (LRRs) and serine/threonine protein kinase (STK) in their encoded products domains. Two primers, XLRRfor/XLRRrev and Pto-kin1/Pto-kin2, were designed on the loci of these conserved domains. By polymerase chain reaction (PCR) and denatured polyacrylamide-gel electrophoresis techniques, disease resistance gene analogues (RGA) amplified on 48 soybean materials. The RGA analysis of 48 cultivars produced 53 amplification bands, 39 of them (73.6 %) showed polymorphic, and they were divided into 7 groups at 0.746 similarity coefficient. Although there was no parallelism relationship in groups be-tween two different types of the clustering, the cultivars with broad resistance spectrum, such as Fengshouhuang, Kefeng 36, and Jimoyoudou could be clustered into the same group. The result indicated RGAP (resistance gene analog polymorphism) technique, combining the resistant spectrum, provides a useful and efficient way to improve the efficiency of parent selection in soybean breeding and to accelerate the process of developing soybean cultivars with resistance.

Expression and Cloning of a Novel Stress Responsive Gene (OsMsr1) in Rice

XU Meng-Liang;CHEN Rong-Jun;ROCHA Pedro;LI Luo-Ye;WANG Man-Ling;XU Guo-Yun;XIA Xin-Jie

Acta Agron Sin. 2008, 34(10):  1712-1718.  doi:10.3724/SP.J.1006.2008.01712

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To understand mechanism(s) underlying stress responses and discover new stress-tolerance genes in rice (Oryza sativa L.), we analyzed a global genome expression profiling of the indica cultivar Pei’ai 64S subjected to cold, drought, or heat stresses. Expression profiles were obtained for leaf and panicle tissues at seedling, booting and heading stages from plants under no stress, or cold, drought or heat stresses using the GeneChip Rice Genome Array (Affymetrix) representing 51 279 transcripts from ja-ponica and indica rice. We identified a large number of genes highly up regulated or down regulated under the stresses. One of these genes, OsMsr1 (Oryza sativa L. Multiple Stresses Responsive Gene 1, GenBank accession: EU284112), was highly induced in leaf and panicle at all the developmental stages, in response to all stresses. The expression profile of OsMsr1 obtained by the microarray analysis was confirmed by quantitative real-time RT-PCR analysis of the gene. The two sets of data matched very well, suggesting that OsMsr1 is a multiple stresses responsive gene in rice. In order to study its function in stress tolerance, we cloned the cDNA of the gene through amplification by RT-PCR. Sequence analysis showed that the cDNA encodes a protein of 89 amino acid residues with M.W. ≈ 10 kD and pI ≈ 5. Searching sequence databases failed to find similarity to any gene of known function, and/or gene/protein domain. Analysis of the putative promoter region for candidate cis-regulatory elements using PlantCARE software (http://bioinformatics.psb.ugent.be/webtools/plantcare/html/) identified 5 matches to cis-elements related to stress re-sponses. Based on the above analyses and results obtained, we propose that OsMsr1 is a novel candidate gene involved in stress tolerance in rice. Further study on the function of the gene is in progress.

Mapping of QTLs Underlying Tolerance to Alkali at Germination and Early Seedling Stages in Rice

CHENG Hai-Tao; JANG Hua;XUE Da-Wei;GUO Long-Biao;ZENG Da-Li;ZHANG Guang-Heng;QIAN Qian

Acta Agron Sin. 2008, 34(10):  1719-1727.  doi:10.3724/SP.J.1006.2008.01719

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A double haploid (DH) population including 120 lines derived from a cross between indica rice (Oryza sativa L.) TN1 and japonica rice CJ06 was used to detect quantitative trait loci (QTLs) for 10-trait relative values of alkali damage at germination period and early seedling stage under 0.15% Na₂CO₃ stress. Correlation analyses showed that alkali damage rate in germination period (ADG) had significant positive correlation with relative germination energy (RGE), relative germination rate (RGR) and relative germination index (RGI), and alkali damage rate at early seedling stage (ADS) had significantly correlation with relative seedling height (RSH), relative root length (RRL), relative root number (RRN) and relative seedling dry weight (RDW). ADG and ADS can be used as evaluation indexes of alkaline tolerance in rice. By using QTLNetwork 2.0 software, 14 additive QTLs and 13 epistatic QTLs controlling the tolerance to alkali were mapped. Two main effect QTLs were detected in same region, RM251–RM3280, on chromosome 3, and three main effect QTLs were mapped between RM3286 and RM1279 on chromosome 7. Epistasis analysis showed that some epistatic loci, like RM1–RM1195, RM1358–RM290, RM1279–RM505, and RM1246– RM519 on chromosome 1, 2, 7, and 12 respectively were important under alkali stress, included two or more epistatic QTLs, in-dicating that the QTLs displayed their effects through different ways of interaction. Among the key loci under alkali stress one may be pleiotropic or some closely linked each other. Comparing QTLs with those found in other researches, some alkali resis-tance QTLs were likely to be in the same region with some salt resistance QTLs. A presume was made that QTLs in this article might include two types, one for resistance to ions (K⁺ or Na⁺) stress and other for resisttance to high pH stress, the latter may play an important role for tolerance to alkali. Many rice varieties have different resistance QTLs for alkali stress; we can pyramid them through marker-assistant selection to breed varieties suitable to growth in saline-alkalized land.

Genetic Analysis of Rice False Smut Resistance Using Major Gene Plus Polygene Mixed Genetic Model

LI Yu-Sheng;ZHU Zhen;ZHANG Ya-Dong;ZHAO Ling;WANG Cai-Lin

Acta Agron Sin. 2008, 34(10):  1728-1733.  doi:10.3724/SP.J.1006.2008.01728

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Rice false smut, a fungus disease caused by Ustilaginoidea virens (Cooke) Takahashi, has become one of the most important rice diseases in China. It is of practical guiding significance to probe resistant mechanism for programming rice breeding for resistance to false smut. The present study was aimed to estimate the genetic model and genetic parameters of rice false smut resistance using the artificial inoculation technique to induce the rice false smut efficiently, and the disease rate index scored based on percentage of the infected grains. The experiment was conducted using 157 recombinant inbred lines (RILs) population of F10 derived from a cross of IR28 (indica) ´ Daguandao (japonica), two parents exhibited resistant and susceptible to rice false smut respectively. The results showed that the rice false smut resistance was controlled by two major genes plus polygene mixed ge-netic model (model E-1-3), and two major genes had equivalent additive effect of 11.41, their heritability was about 76.67%, while the heritability of polygene was about 22.86%. The resistance to rice false smut had significant major gene effect, and the results implied that not only major gene’s effect but also polygene’s effect should be considered in breeding for resistance to rice false smut.

Interval Mapping of Quantitative Trait Loci Underlying Endosperm Traits with NC III and TTC Designs

WANG Xue-Feng;TANG Zai-Xiang;WANG Ya-Min;SONG Wen;XU Chen-Wu

Acta Agron Sin. 2008, 34(10):  1734-1743.  doi:10.3724/SP.J.1006.2008.01734

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The endosperm of cereal crops is a triploid tissue produced by a male gamete from the pollen grain fusing with two female nuclei. Endosperm traits refer to those characteristics that determined by the physical and chemical properties of grain endosperm. Because many quality traits are closely related to endosperms, the genetic study of endosperm traits plays a fundamental and vital role in improving grain quality. There have been several publications detailing the unique properties of endosperm traits. A series of QTL mapping models and approaches specific for triploid traits have been proposed, using single grain observation or more practical one that obtained from bulked samples. However, current methods based on bulked samples often fail to estimate two dominance effects of endosperm QTL separately, or involve a heavy work of crossing. On the basis of quantitative genetic models for triploid endosperm traits, a new mapping approach based on North Carolina Design III (NC III) and Triple Test Cross (TTC) was proposed in this study. Feasibility and efficacy of the method were investigated through simulated data. Experimental factors considered in the simulations include QTL heritability, number of plants in F₂ population, and number of endosperms collected per family. The results suggested that the two methods had satisfactorily high detection powers, which reached 100% even when the QTL heritability was 5%. But the TTC-based approach tended to have slightly higher power than the NC III-based one. Both approaches can distinguish two dominance effects successfully. But overall, the TTC-based approach can offer better estimation of either QTL position or effect, though this superiority waned as the heritability and sample size increase.

Combining Ability and Genetic Effects of Germination Ability in Different Brassica napus L. Cultivar under Simulated Drought Stress

YANG Chun-Jie;CHENG Yong;ZOU Chong-Shun;ZHANG Xue-Kun;ZHENG Pu-Ying;LI Gui-Ying;YANG Chang

Acta Agron Sin. 2008, 34(10):  1744-1749.  doi:10.3724/SP.J.1006.2008.01744

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The rapeseed breeding for tolerance to drought is one of the most important ways to reduce yield loss from drought stress in autumn. Therefore, an experiment was conducted to estimate combining ability and heritability of drought tolerance during seed germination using complete diallel crossing design of seven cultivars. The germinating seeds of parents and F1 were treated with simulated drought stress in 10% PEG and grew for 7 d, then relative length of stem, relative fresh weight per plant, relative survival percentage, relative germination rate, relative germination energy, and relative vigor index were measured, general combining ability and special combining ability of germination traits were analyzed by Griffing I. The results showed that general combining ability was significantly different in six drought traits. And meanwhile special combining ability in five traits was significantly different except relative vigor index. Among 42 combinations, Zhongshuang 9 had the highest general combining ability effect values of six traits above which were 0.0708, 0.0656, 0.1185, 0.1048, 0.1096, and 0.0861, respectively. Although the general combining ability of Zhongshuang 6 was not very high, but the special combining ability of its combinations Zhong-shuang 6 × Xinongchangjiao and Zhongshuang 6 × Zhongshuang 10 was higher. The combinations can be used in rapeseed breeding for drought tolerance.

QTL Mapping for Grain Filling Rate and Thousand-Grain Weight in Dif-ferent Ecological Environments in Wheat

WANG Rui-Xia;ZHANG Xiu-Ying;WU Ling;WANG Rui;HAI Lin;YAN Chang-Sheng;YOU Guang-Xia;XIAO Shi-He

Acta Agron Sin. 2008, 34(10):  1750-1756.  doi:10.3724/SP.J.1006.2008.01750

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The duration and rate of grain filling determine the individual grain size, thousand-grain weight (TGW), and final grain yield. Several reports have focused on the physiological basis of grain filling in wheat (Triticum aestivum L.), but rare on the genetic mechanism and QTL mapping due to its complexity. To identify QTLs related to grain filling, the F_7:8 generation of 142 recombinant inbred lines (RILs) derived from the cross between Yu 8679 (large spike) and Heshangmai (small spike) were planted in four ecological environments in Beijing (2006 and 2007), Hefei (2007), and Chengdu (2007). Three agronomic traits including mean grain filling rate (GFR_mean), maximum grain filing rate (GFR_max), and TGW were evaluated. A genetic map comprising 170 SSR and 2 EST markers (Tx23-24 and Tx37-38) was constructed based on the 142 RILs. According to the genetic map and phe-notypic data, quantitative trait loci were identified for these agronomic traits using the composite interval mapping (CIM) method. A total of 54 QTLs located on chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 3D, 4A, 4D, 5A, 5B, 6D, and 7D for the three traits were identified over four environments. Among them, 17 for GFR_mean, 16 for GFR_max, and 21 for TGW, accounted for variations of GFR_mean, GFR_max, and TGW by 7.17–20.83%, 6.31–15.95%, and 4.36–16.80%, respectively. Ten genomic sections involving chromosomes 1A, 1B, 2A, 3B, 4D, 6D, and 7D with “pleiotropic effects” were detected. These QTLs with pleiotropic effects are useful for understanding the relationship between grain filling and other related grain yield traits at gene level.

Linkage Relationship between T-type Restorer Gene Rf3 and K-type Male Sterile Gene rfv1 in Triticum macha L.

SONG Xi-Yue;DONG Pu-Hui;HU Yin-Gang;MA Ling-Jian;LI Hong-Bin;HE Bei-Ru

Acta Agron Sin. 2008, 34(10):  1757-1761.  doi:10.3724/SP.J.1006.2008.01757

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Wheat (Triticum aestivum L.) breeding line Tm3314 is a T-type non-1B/1R material carrying 1BS of T. macha. KTm3314A, a K-type non-1B/1R male sterile line developed from Tm3314, is easily restored in fertility, does not produce haploids in reproduction, and has high temperature-sensitivity, thus has potential in wheat hybrid breeding. The T-type restorer gene Rf3, which is closely linked to K-type male sterile gene rfv1 on 1BS in T. spelta, is used as a marker of rfk1 under the background of T. timophvee cytoplasm. However, some male sterile materials with substitutive chromosome fragments of the 1BS of T. macha have been found the absence of rfv1 under T. timophvee cytoplasm background. To understand the linkage relationship between Rf3 and rfv1 in T. macha, the segregation generations of (T504A/Tm3314) F₂ and T504A//KTm3314A/90(13)21 as well as their backcross populations with a K-type sterile line K119A were used in field experiments in 2003–2006. The results showed that crossing-over value between Rf3 and rfv1 was 16.54%.

Preliminary QTL Analysis of Several Chemical Components in Flue- Cured Tobacco (Nicotiana tabacum L.)

XIAO Bing-Guang;LU Xiu-Ping;JIAO Fang-Chan;LI Yong-Ping;SUN Yu-He;GUO Zhao-Kui

Acta Agron Sin. 2008, 34(10):  1762-1769.  doi:10.3724/SP.J.1006.2008.01762

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The chemical components are the important traits influencing the leaf quality of tobacco. QTLs linked to the chemical components can be used for marker-assisted selection in leaf quality improvement in tobacco. The objective of this study was to identify QTLs linked to several chemical components in the flue-cured tobacco. A population of 137 doubled haploid (DH) lines derived from a cross between two flue-cured tobacco cultivars G-28 and NC2326 was employed to construct the genetic linkage map. Twenty-three new markers were obtained by ISSR and RAPD analysis, and were combined with the previous marker data for the construction of linkage map. A genetic linkage map consisting of 11 ISSR markers and 158 RAPD markers was developed. The map consisted of 27 linkage groups and spanned 2 094.60 cM with an average distance of 15.95 cM between adjacent markers. The data for three chemical components including total sugar (TS), nicotine (NIC) and potassium oxide (KO) were collected from a field experiment conducted in four different environments, and a full-QTL model and the corresponding mapping software were used for the preliminary QTL analysis. Seven additive effect QTLs and nine pairs of epistatic QTLs were detected. The results indicated that epistasis played important roles in the genetic basis of the chemical components in the flue-cured tobacco. For the epistatic QTLs, in which the individual QTL showed no additive effect, it should be efficient to select the QTL combinations rather than the single QTL. Three additive QTLs and three pairs of epistatic QTLs were found to involve in QTL-by-environment interactions (QE): The additive QTL-by-environment interactions were detected for NIC and KO, and the epistatic QTL-by-environment interactions were detected for TS and KO. QTL-by-environment interactions presumably arise from the differential gene expression in various environments and their application in marker-assisted breeding programs would require careful consideration with regard to a particular set of environmental conditions. The present study provides a starting point for detecting QTLs for economically important traits and for understanding the genetic basis of the traits.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Differences in Tolerance to Low-Potassium Supply among Different Types of Cultivars in Cotton (Gossypium hirsutum L.)

TIAN Xiao-Li;WANG Gang-Wei;YANG Fu-Qiang;YANG Pei-Zhu;DUAN Liu-Sheng;LI Zhao-Hu

Acta Agron Sin. 2008, 34(10):  1770-1780.  doi:10.3724/SP.J.1006.2008.01770

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Commercial cotton production is currently limited by varying levels of potassium (K) deficiency in China. Investigating tolerance to low-potassium (TTLP) of different types of cultivars is important for choosing the adaptive cultivars to guide the potassium fertilizer application in cotton production. Forty-eight cotton cultivars, mainly predominant cultivars/lines developed in China in 2004, were classified into transgenic insect-resistant cotton (TIRC, thirty-three cultivars) and non-insect-resistant cotton (NIRC, fifteen cultivars) / conventional cotton (CC, thirty-three cultivars) and hybrid cotton (HC, fifteen cultivars) / different-maturity cotton. The dry weight (DW), K⁺ absorption amount (KAA) and internal utilization index (total plant biomass produced per unit K concentration, KUI) of seedlings in a low K⁺ (0.02 mmol L^-1) solution and dry weight of reproductive organs (FRDW, including squares, flowers and uncracked and cracked bolls) in a field with potassium-deficient soil (59.88 mg kg^-1) were compared among different types of cultivars. The results indicated that TTLP of TIRC was inferior as compared with that of NIRC, and DW, KAA and KUI at seedling stage and FRDW in a field decreased by 20.1% (P<0.01), 15.0% (P<0.05), 23.7% (P<0.01) and 20.9% (P<0.05), respectively. Additionally, five cultivars concerning minimum DW of seedlings were all TIRC, and four out of five cultivars concerning minimum FRDW were TIRC. Thus the foreign genes (Bt and CpTI) encoding insecticidal protein and their introduction processes surely affected TTLP of cotton. However, the underlying mechanisms controlling TTLP still remained unclear. HC showed greater TTLP as compared to CC; with 28.0%, 19.9%, 26.4%, and 43.2% increase in DW, KAA, KUI, and FRDW, respectively. In addition, four from five cultivars concerning maximum both DW and FRDW were HC. These suggested that TTLP of cotton showed significant heterosis. It was further found that the heterosis of TIRC in TTLP was higher than that of NIRC. For example, DW, KAA, KUI, and FRDW of hybrid TIRC were 37.0%, 24.6%, 44.3%, and 59.4% higher, respectively, than those of conventional TIRC, whereas hybrid NIRC only showed 27.7% and 29.9% higher in DW and FRDW, respectively, than conventional NIRC. However, maturity did not affect TTLP of cotton. Significant genotypic variation in TTLP was also observed within each type of cultivars. TTLP of the best cultivars of conventional TIRC was equal to that of the middle cultivars of conventional NIRC and hybrid TIRC.

Effects of Key Enzyme Activities in Sucrose Metabolism on Fiber Quality in High Quality Upland Cotton

LIU Juan;SONG Xian-Liang;ZHU Yu-Qing;LI Xue-Gang;CHEN Er-Ying;SUN Xue-Zhen

Acta Agron Sin. 2008, 34(10):  1781-1787.  doi:10.3724/SP.J.1006.2008.01781

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Fiber strength is an important index that measures the fiber quality, which determined by cellulose deposition characteristics. Cellulose synthesis and accumulation are affected by many enzymes including sucrose synthetase (SS), sucrose phosphate synthetase (SPS) and so on. Up to date, there have been few reports about cellulose accumulation and key enzymes relating to sucrose metabolism in high quality upland cotton cultivars. To investigate the relationship between fiber quality differences and relating sucrose metabolism enzymes, a filed experiment was conducted at Shandong Agricultural University in 2006–2007. Three upland cotton cultivars including Ludimianlu 324 and Yumian1(YM-1) (high quality) and Lumianyan (18) (common quality) were used in the experiment. Leaves were sampled at 15, 30, 45, and 60 days after leaf unfolding. Flowers were labeled at anthesis and sampled every 7 days from 7 days after anthesis. The result showed that the sucrose content was higher with higher SPS activities in high quality upland cotton leaves. The simulation with Logistic equation of cotton cellulose accumulation showed that the accumulation duration was longer and the accumulation rate was moderate, so the final cellulose content was higher in high quality upland cotton cultivar. Compared with common upland cotton, the sucrose content was higher in fiber at early growth stage in high quality upland cotton, which supplied enough original substrate for secondary wall thickening. Meanwhile, the SS activity was higher and consistent with cellulose accumulation duration in high quality upland cotton. Furthermore, high quality upland cotton had higher SPS activity before termination of cellulose accumulation duration. It was suggested that SPS activity in leaves, SS and SPS activities in fibers had close correlation with cellulose accumulation and fiber quality.

Development of Small Starch Granule in Barley Endosperm

WEI Cun-Xu;ZHANG Jun;ZHOU Wei-Dong;CHEN Yi-Fang;XU Ru-Gen

Acta Agron Sin. 2008, 34(10):  1788-1796.  doi:10.3724/SP.J.1006.2008.01788

Abstract ( 1997 )   PDF (6007KB) ( 1518 )   Save

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Mature starchy endosperm of barley is mainly composed of starch. The structural characteristics and physicochemical properties of barley starch differ with granule size, which is important in final product applications of barley flours. To produce barley cultivars with predominantly large or small starch granules, it is necessary to understand the development of large and small starch granules during barley endosperm development. However, only large starch granule in barley has been studied currently, while little information is available on small starch granule development. In this study, we used Yangsimai 3 as the material to investigate small starch granule development in barley endosperm. Starch granules in barley mature endosperm showed a three-size distribution after differential sedimentation. The average long axis of A-, B-, and C-type starch granules was 16.1, 7.9, and 2.6 mm, and their percentage in total starch weight was 87.2%, 11.9%, and 0.9%, respectively. Large starch granule (A-type) increased quickly in size with approximate maximum diameter at 12 days after ear stem emerging from flag leaf sheath (DAE). The number of large starch granules in endosperm cell changed little after 16 DAE. Small starch granules (B- and C-types) initi-ated at 12 DAE and increased quickly in number from 12 to 20 DAE. After 20 DAE, the magnitude of increase in number of small starch granules reduced. Scanning electron micrographs indicated that large starch granules showed a disk shape and small starch granules showed a spherical or irregularly polygonal shape. Endosperm cells had large amyloplast that exhibited protrusions from envelope at 10 DAE. Spherical small amyloplast appeared at 12 DAE and increased quickly in number at 20 DAE. Some small amyloplasts showed polygonal shape at 24 DAE. Many irregularly polygonal small starch granules were observed around large starch granules after 28 DAE. Transmission electron micrographs with conventional glutaraldehyde-osmium tetroxide fixation showed that early endosperm cells contained amyloplasts that contained single starch granule. Large amyloplasts with large starch granules divided and increased in number through binary fission at 12 DAE. One large amyloplast had only one large starch gra- nule. The envelopes of large and small amyloplasts were difficultly observed after 12 DAE. Transmission electron micrographs with potassium permanganate fixation showed a distinct endomembrane organization, in particular, the structure associations of the amyloplast envelope with amyloplast proliferation during endosperm development. Endosperm cells had large amyloplasts that exhibited protrusion at 12 DAE, and some of the protrusions contained small starch granules. Small amyloplasts with small starch granules formed new small amyloplasts to produce small starch granules by the way of protruding of their envelopes at 16 DAE. Many small starch granules formed and developed in one small amyloplast. With small starch granules development in one small amyloplast, some small starch granules became irregularly polygonal shape when they enlarged close to one another. The amyloplast envelope began to degrade and released starch granules into cell matrix when amyloplast was full of starch granules. The above results showed that small amyloplasts came from the protrusion of amyloplast envelopes. Many small starch granules, which were compound starch granules, formed and developed in one small amyloplast.

Comparison and Cluster Analysis of Photosynthetic Characters and Water Use Efficiency in Tea (Camellia sinensis) Cultivars

GUO Chun-Fang;SUN Yun;CHEN Chang-Song;CHEN Rong-Bing;ZHANG Mu-Qing

Acta Agron Sin. 2008, 34(10):  1797-1804.  doi:10.3724/SP.J.1006.2008.01797

Abstract ( 1889 )   PDF (511KB) ( 1507 )   Save

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The importance of carbon input in tea productivity can be appreciated from the fact that 95% of the dry weight of the plant is derived from photosynthesis. Therefore, an increase in net photosynthesis and more efficient partitioning are logical steps for increasing productivity, which was subject to the tea genotypes. The photosynthetic parameters in leaves of 52 tea cultivars were determined under field conditions, and studied by using phenetic classification, principal component, cluster, discrimination analyses. The results showed that there were significant differences (P<0.01) in net photosynthesis rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), water use efficiency (WUE) among the tested cultivars. The first three principal components were analyzed and their cumulative contribution of variance accounted for 96.98%. P_n, T_r, and G_s were the main factors in the first principal component. WUE and C_i were the main factors in the second and third principal com-ponents respectively. Fifty two tea cultivars were clustered into five groups based on P_n, T_r, G_s, and WUE. The group I including 15 tea cultivars with high photosynthesis rate, medium transpiration rate, lower stomatal resistance and high water use efficiency could be used for improvement of tea cultivars. Then, with discrimination analysis, the parameters of P_n, T_r, G_s, and WUE greatly affecting the classification were selected, and five discrimination models with better distinguishing ability were set up.

Photosynthetic Characteristics and Photoprotective Mechanisms in Highland Barley

CHENG Ming;LI Zhi-Qiang;JIANG Chuang-Dao;SHI Lei;TANG Yu-Dan;ZHANG Jin-Zheng

Acta Agron Sin. 2008, 34(10):  1805-1811.  doi:10.3724/SP.J.1006.2008.01805

Abstract ( 1786 )   PDF (598KB) ( 1563 )   Save

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As a local crop of Qinghai-Tibet Plateau, highland barley (Hordeum vulgare L.) has acclimated to the typical habitat with strong light and low O₂ to CO₂ ratio. Low O₂ to CO₂ ratio may have a great influence on photorespiration which plays an important role in protecting photosynthetic apparatus against photoinhibition. In this study, we hope to know whether photorespiration plays an important role in photoprotection of highland barley and what are the main photoprotective mechanisms of highland barley. Gas exchange, fluorescence quenching kinetics and reflectance spectrum were investigated to explore the photosynthetic characteristic and allocation of excitated energy in two highland barley cultivars. Results showed that light saturation point of highland barley was about 1 000 μmol m^-2 s^-1. Photorespiration rate (P_r) increased with light intensity increasing while it did not change significantly above 500 mmol m^-2 s^-1. The percentage of photorespiration to total photosynthesis (P_r/P_m) declined gradually with the increase of light intensity. The efficiency of open centers of photosystem II (F_v’/F_m’), actual photosystem II efficiency (Φ_PSII) and photochemical quenching (qP) all declined with the increase of light intensity; non-photochemical quenching increased with light intensity increasing, indicating that more and more excited energy dissipated as thermal dissipation. Spectrum analysis showed that the change of photochemical reflectance index (△PRI) increased significantly when fully dark-adapted plants were suddenly exposed to light. On these bases, we concluded that photorespiration is not the main pathway for highland barley to relieve strong light stress; thermal dissipation relying on xanthophyll cycle may play an important role in dissipating excessive excited energy in highland barley.

Monitoring Canopy Chlorophyll Density in Seedlings of Winter Wheat Using Imaging Spectrometer

TAN Hai-Zhen;LI Shao-Kun;WANG Ke-Ru;XIE Rui-Zhi;GAO Shi-Ju;MING Bo;YU Qing;LAI Jun-Chen;LIU Guo-Qing;TANG Qiu-Xiang

Acta Agron Sin. 2008, 34(10):  1812-1817.  doi:10.3724/SP.J.1006.2008.01812

Abstract ( 2141 )   PDF (1314KB) ( 2022 )   Save

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Imaging spectrometer is a new kind of remote sensing sensor, which receives images of ground objects and their spectrum components. It has great potentials in accurately quantitative analysis with remote sensing of high spatial and spectral resolutions. MSI200 is an imaging spectrometer manufactured by the authors. It was used in this study to monitor canopy chlorophyll density in winter wheat (Triticum aestivum L.) at seedling stage in comparison with ASD Fieldspc FR2500, a well-known non-imaging spectrometer. Correlation analysis showed that R720, FD660, FD550, TCARI, GNDVI, PPR (550, 450), and NRI obtained by the 2 spectrometers were both significantly correlated (P<0.01) with canopy chlorophyll density. This primarily indicated the reliability of MSI200. The precisions of predicted model on chlorophyll density were 91.26–95.54% and 86.61–92.79% for MSI200 and ASD Fieldspc FR2500, respectively. Among these parameters, PPR was the best one to monitor canopy chlorophyll density with root mean square error (RMSE) of 0.0979 and 0.8391 for MSI200 and ASD Fieldspc FR2500, respectively. Compared with the traditional non-imaging spectrometers, MSI200 predicted better the canopy chlorophyll density in wheat with smaller errors, and the selected wavelengths were important to spaceflight and airborne remote sense.

Effects of Simulated Salt and Alkali Conditions on Seed Germination and Seedling Growth of Sunflower (Helianthus annuus L.)

LIU Jie;ZHANG Mei-Li;ZHANG Yi;SHI De-Cheng

Acta Agron Sin. 2008, 34(10):  1818-1825.  doi:10.3724/SP.J.1006.2008.01818

Abstract ( 1989 )   PDF (352KB) ( 1945 )   Save

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Salinization and alkalization of soil are a widespread environmental problem, including salt-stress and alkali-stress in terms of the salt characteristics. In fact, the destructive effects caused by alkali-stress are more serious than that by salt-stress. The resistance to salt- and alkali-stress of sunflower (Helianthus annuus L.) is stronger than that of the other crops, as some sunflowers are able to grow on alkalinized soil. The stress conditions of 6 salinities and 6 alkalinities were simulated by mixing two neutral salts (NaCl and Na₂SO₄) and two alkaline salts (NaHCO₃ and Na₂CO₃) both in the molar ratio of 9:1 respectively. The concentration range of treatments was from 40 to 240 mmol L^-1 for the salt-stress, and 10 to 60 mmol L^-1 for the alkali-stress. A sunflower cultivar Baikuiza 6 with higher resistance to salt-alkaline stresses, was used to determine emergence time, emergence rate, survival seedling rate, and physiological indexes including leaf area, water content, biomass of seedlings, and content of Na⁺ and K⁺ under salt- and alkali-stresses. The results showed that the maximum intensity of salt-stress for baikuiza 6 germination and seedling growth was pH 6.98 and electric conductivity of 1.311 dS m^-1 in the culture medium, and alkali-stress was pH 9.71 and electric conductivity of 0.360 dS m^-1. Under the salt or alkali conditions that seedlings could be able to grow, not only the emergence rate and survival seedling rate decreased, but also the time of emergence delayed significantly with the increasing intensity of salt-stress. Whereas the survival seedling rate decreased and the emergence time didn’t delay with the increasing of alkali-stress intensity. Moreover, various growth indexes of seedling decreased with increasing intensity of salt- or alkali-stress, and the extent of decrease was greater under alkali-stress than under salt-stress. In conclusion, the mechanisms of salt- and alkali-stresses effects on germination and seedling growth of sunflower are different, and the tolerance and response of sunflower to the both stresses are different during the two growing stages, proving that salt-stress and alkali-stress are two kinds of stresses.

Grain Morphological Traits Measured Based on Vision Detection Tech-nology and Their Relation to Grain Weight in Rice under Different Water Condition

ZHANG Wei-Xing;ZHU De-Feng;XU Yi-Cheng; LIN Xian-Qing; ZHANG Yu-Ping;CHEN Hui-Zhe;ZHAO Zhi;ZHOU Ping

Acta Agron Sin. 2008, 34(10):  1826-1835.  doi:10.3724/SP.J.1006.2008.01826

Abstract ( 2151 )   PDF (1026KB) ( 1302 )   Save

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Based on machine vision detection technology, with Shanyou 63 (a representative common hybrid rice) and Guodao 6 (a super hybrid rice) as experiment materials, designed different water treatment from beginning to 30 days after panicle initiation and determined soil moisture by W.E.T Sensor (ML2x type, made in USA) and electronic balance (made in Shanghai, China), the grain morphological traits of full panicle and different position within a rice panicle under different water condition was studied, the relationship among these traits and their relation to grain weight was analyzed. The results indicated that the response of grain length, projective area, and 1000-grain weight to soil moisture was more obvious, the change of GRWA (ratio of grain weight to area) was caused by the effect of water deficit on grain area and weight, the response of ratio of grain length to width manifested complexity in a certain extent, and that of grain width to water was different in Shanyou 63 and Guodao 6. The grain morphologi-cal traits, yield and its components showed a drop trend of different extent with enhanced degree of water deficit, these grain morphological traits and grain weight reduced observably while controlling soil moisture from beginning to 30 days after panicle initiation, the effect of water deficit was most significant during 0–30 d control water, secondary, during 10–20 d heavy or middle water deficit and 0–10 d or 20–30 d heavy water deficit. The expressive laws of the effect of controlling water at different stage on grain morphological traits and weight of different position within a panicle was basically inosculated with the order of panicle initiation, growth and development. Among these morphological traits (except for width) all showed significant positive correla-tion at 0.01 probability level, while the relationship of grain width with other morphological traits was significant negative corre-lation at 0.01 or 0.05, respectively. The correlativity existed significantly between grain weight and grain length, projective area and ratio of grain length to width at 0.01 or 0.05, respectively. Therefore, the three traits can be used as grain morphological effec-tive index to appraise drought-resistance in rice.

Effects of Soil Texture on Activities of SPS, SS, and Relationship with Starch Accumulation during Grain Filling in Wheat

WANG Wen-Jing;HE Jin-Huan;LIAN Yan-Xian

Acta Agron Sin. 2008, 34(10):  1836-1842.  doi:10.3724/SP.J.1006.2008.01836

Abstract ( 2089 )   PDF (651KB) ( 1195 )   Save

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A wheat (Triticum aestivum L.) cultivar, Yumai 49 was used in a pool experiment to investigate the activities of key enzymes involved in sucrose metabolism in leaf, sheath, stem, and grain during grain filling in clay-loam, mid-loam, and sand-loam soils. The changes of sucrose phosphate synthase (SPS) and sucrose synthase (SS) activities in different organs during grain filling in three types of soil showed a single-peak curve. In the sand-loam soil, SPS activities were the highest in different organs expect grains. In the mid-loam soil, the SPS activity in grains at the early filling stage and the SS activity at the medium-to-late filling stages were significantly higher than those in the clay-loam soil. The 1000-grain weight and starch content in the mid-loam soil and sand-loam soil were significantly highter than those in the clay-loam soil, but those were not significantly different between mid-loam soil and sand-loam soil. This showed that the mid-loam soil and sand-loam soil could affect the sucrose synthesis and degradation in Yumai 49. The sand-loam soil was available for sucrose synthesis in the vegetative organs of wheat, but the mid-loam soil was available for sucrose synthesis in grains of wheat. The SPS and SS activities all correlated significantly or very significantly with grain filling rate, amylopectin and starch accumulation rates in grains in the mid-loam soil and sand-loam soil, but the correlation between the enzymes activities, expect SPS activities in grains, and starch accumulation rate was not significant. It is more important for the sucrose synthesis catalyzed by SPS in the vegetative organs and the sucrose degradation catalyzed by SS in grains to accumulate the starch and amylopectin in grains of wheat in the mid-loam soil and sand-loam soil.

RESEARCH NOTES

Cloning a New Member from Glu-B3 Locus in Durum Wheat and Deve- loping Its Specific Marker

ZHAO Yong-Tao;KONG Xiu-Ying;ZHAN Ke-Hui

Acta Agron Sin. 2008, 34(10):  1843-1848.  doi:10.3724/SP.J.1006.2008.01843

Abstract ( 1940 )   PDF (1177KB) ( 1247 )   Save

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A new member of Glu-B3 gene family was isolated from durum wheat Langdon variety. According to the alignment of the conserved N- and C- terminal domains of the deduced amino-acid of LMW-GS genes in GenBank, a pair of degenerate primers was designed. Using this primer pair, an M-type LMW-GS gene was identified from Langdon. The gene, designated as LMWLDN-M, encodes 350 amino acids. Compared with other sequences of Glu-3 isolated from Langdon in our laboratory, a SNP was detected and thus a gene specific marker was developed. This marker can also be used to map the gene LMWLDN-M onto the chromosome 1B using LDN D-genome disomic substitution lines and CS nulli-tetrasomic lines as templates. By comparison with other members of Langdon isolated before, we confirm that LMWLDN-M is a new member of Glu-B3 family. After sequencing the BAC carrying this gene, it can help us to understand the complex Glu-3 loci well.

Effects of Exogenous Nitric Oxide Donor SNP on Contents of Chlorophyll and Free Proline, Activity of Antioxidative Enzyme in Rice Seedlings under NaCl Stress

XIAO Qiang;CHEN Juan;WU Fei-Hua;ZHENG Hai-Lei

Acta Agron Sin. 2008, 34(10):  1849-1853.  doi:10.3724/SP.J.1006.2008.01849

Abstract ( 2127 )   PDF (238KB) ( 2049 )   Save

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In this study, the contents of chlorophyll, free proline and the activities of GPX, SOD, CAT, and the producing rate of superoxide radicals in rice seedlings treated with a varying concentration of SNP under 100 mmol L^-1 NaCl stress were investigated. The results showed that the contents of chlorophyll and free proline increased by treatment with low SNP concentration under salt stress. SNP alleviated significantly the oxidative damage caused by salt stress in leaf and root of rice seedlings. Different enzyme activities were regulated by SNP between leaf and root in rice seedlings under salt stress, SNP alleviated significantly the oxida-tive damage via promoting SOD and CAT activities in rice leaf, whereas, via regulating GPX activity mainly besides promoting SOD and CAT activities in root.

Changes of Oil Content and Oil Biosynthesis-Related Enzymes Activities and Their Correlation during Seed Formation in Brassica napus

XU Yi-Lan;GUAN Chun-Yun;TAN Tai-Long;YU Long-Xi

Acta Agron Sin. 2008, 34(10):  1854-1857.  doi:10.3724/SP.J.1006.2008.01854

Abstract ( 1877 )   PDF (415KB) ( 1245 )   Save

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Two lines of rapeseed with high and low oil contents respectively which have the same genetic background were used to study the dynamic changes of oil-content, glucose 6-phosphate dehydrogenase (G6PDH) activity, and phosphatidate phosphatase (PPase) activity during seed formation, and the correlation between enzymes and oil content in Brassica napus was analysed. The results showed that Oil content, G6PDH activity, and PPase activity increased gradually and reached the peak at 24–31 d after flowering. Significant correlation between two lines in oil content, G6PDH activity and PPase activity were existed; G6PDH and PPase activities were significantly correlated with oil content. From the results above, we can come to the inference that G6PDH and PPase are the key factors affecting oil content.

SSR Analysis of New Developed Soybean Lines Resistant to Soybean Cyst Nematode (Heterodera glycines Ichinohe) Race 4

YUAN Cui-Ping;LU Wei-Guo;LIU Zhang-Xiong;LI Ying-Hui;LI Wei-Dong;GUAN Rong-Xia;CHANG Ru-Zhen;QIU Li-Juan

Acta Agron Sin. 2008, 34(10):  1858-1864.  doi:10.3724/SP.J.1006.2008.01858

Abstract ( 1955 )   PDF (615KB) ( 1264 )   Save

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Soybean cyst nematode (SCN, Heterodera glycines) is a seriously destructive pest in soybean production worldwide and causes great yield loss every year. Planting resistant variety is an effective and economical method to decrease its damage. At present we obtained 41 elite soybean lines from the crosses of Hartwig × Jin 1261, Hartwig × Jin 1265 and Hartwig × Jin 1267, and genotyped them with 130 SSR markers from 20 linkage groups of soybean, in order to provide new soybean germplasm as well as molecular markers used in soybean breeding for resistance to SCN. The results suggested that Hartwig and Jin 1261, Jin 1265 or Jin 1267 had different resistance genes to SCN 4, with genetic similarity of 0.362. Twenty-two SSR markers from 11 linkage groups were associated with resistance to SCN 4, and at Satt684, Sat_230, Sat_222, Satt615 and Satt231 loci, the allele from Hartwig was resistant type, while the allele from Jin 1261, Jin 1265 and Jin 1267 was susceptible one, on the contrary at the other 17 SSR loci, the allele from Hartwig was susceptible type, while the allele from Jin 1261, Jin 1265 and Jin 1267 was resistant one. We supposed that Jin strains had at least a new resistance gene on linkage group D1b. We could effectively identify the resistance of these soybean lines to SCN 4 with Satt684 and Sat_400.

Preliminary Identification of a Novel Sanming Dominant Male Sterile Gene in Rice (Oryza sativa L.)

HUANG Xian-Bo;TIAN Zhi-Hong;DENG Ze-Qin;ZHENG Jia-Tuan;LIN Cheng-Bao;TANG Jiang-Xia

Acta Agron Sin. 2008, 34(10):  1865-1868.  doi:10.3724/SP.J.1006.2008.01865

Abstract ( 1901 )   PDF (377KB) ( 1365 )   Save

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In the studies on the fertility in Fengyuan village, Xicheng town, Youxi county, Fujian province in 2001, a special sterile plant was found in the F₂ populations of No. S221 from combination SE21S/Basmati 370. Its pollen abortion type was different from others. From the studies of test-crossing, back-crosses and sib-crossing, sterile and fertile plants segregated in a 1:1 ratio in the descendant populations. When the sterile plant was used as female parent and crossed to normal variety, sterile and fertile plants segregated in a 1:1 ratio in the descendant populations also, and no sterile plants cound be separated from fertile plants. All of the results proved that the male sterility of S221 is controlled by one pair of dominant male sterility gene.