Fine mapping of locus S-b for F1 pollen sterility in rice （Oryza sativa L.）

Strong heterosis existed in the hybrid of the subspe-cies in rice[1,2]. However, the partial sterility of the hy-brid hinders the utilization of the heterosis[3,4]. Ikehashi et al.[5,6] considered the female gamete as the main ste-rility form and proposed…     

Genetic diversity of rice cultivars （Oryza sativa L.） in China and the temporal trends in recent fifty years

Public concern is often expressed at cultivars because the domestication and modern plant breeding have led to a reduction in the genetic diversity of crops and loss of genes, which could result in crops' genetic vulnerability to changes in the spectrum of pestssity of varieties in this zone is very important to the whole rice production in China. REZV, a important japonica rice production areas with more than 278 thousands ha rice which was about 71% of rice area in north China, accounted fo…     

Genetic analysis and mapping of rice （Oryza sativa L.） male-sterile （OsMS-L） mutant

A rice male-sterile mutant OsMS-L of japonica cultivar 9522 background, was obtained in M4 population treated with ^60Co γ-Ray. Genetic analysis indicated that the male.sterile phenotype was controlled by a single recessive gene. Results of tissue section showed that at microspore stage, OsMS-L tapetum was retarded. Then tapetal calls expanded and microspores degenerated. No matured pollens were observed in OsMS-L anther locus. To map OsMS-L locus, an F2 population was constructed from the cross between the OsMS-L (japonica) and LongTeFu B(indica). Firstly, the OsMS-L locus was roughly mapped between two SSR markers, RM109 and RM7562 on chromosome 2. And then eleven polymorphic markers were developed for further fine fine-mapping. At last the OsMS-L locus was mapped between the two lnDel markers, Lhsl0 and Lhs6 with genetic distance of 0.4 cM, respectively. The region was delimited to 133 kb. All these results were useful for further cloning and functional analysis of OsMS-L.     

Genetic analysis and molecular mapping of a presenescing leaf gene psll in rice （Oryza sativa L.）

A rice psl1 （presenescing leaf） mutant was obtained from a japonica variety Zhonghua 11 via radiation of ^60Co-γ in M2 generation. Every leaf of the mutant began to wither after it reached the biggest length, while the leaves of the wild variety could keep green for 25--35 d. In this study, genetic analysis and gene mapping were carried out for the mutant identified. The SSR marker analysis showed that the mutant was controlled by a single recessive gene （psl1） located on chromosome 2. Fine mapping of the psl1 locus was conducted with 34 new STS markers developed around psl1 anchored region based on the sequence diversity between Nipponbare and 93-11. The psl1 was further mapped between two STS markers, STS2-19 and STS2-26, with genetic distances of 0.43 and 0.11 cM, respectively, while cosegregated with STS2-25. A BAC contig was found to span the psl1 locus, the region being delimited to 48 kb. This result was very useful for cloning of the psl1 gene.     

Fine mapping of a semidwarf gene sd-g in indica rice（Oryza sativa L.）

The semidwarf gene sd-g which has been usedin indiea rice breeding in southern China is a new one, non-allelic to sd-1. To map sd-g, an F2 population derived fromthe cross between Xinguiaishuangai and 02428 was con-structed. The sd-g was roughly mapped between two mi-crosatellite markers RM440 and RM163, with genetic dis-tances of 0.5 and 2.5 cM, respectively. Then nine new poly-morphic microsatellite markers were developed in this region.The sd-g was further mapped between two microsatellitemarkers SSR5-1 and SSR5-51, with genetic distances of 0.1and 0.3 cM, respectively, while cosegregated with SSR418. ABAC contig was found to span the sd-g locus, the region be-ing delimited to 85 kb. This result was very useful for cloningof the sd-g gene.     

Genetic basis of heterosis and inbreeding depression in rice （Oryza sativa L.）

The genetic basis of heterosis was studied through mid-parent, standard variety and better parent for 11 quantitative traits in 17 parental lines and their 10 selected hybrids in rice (Oryza sativa L.). The characters were plant height, days to flag leaf initiation, days to first panicle initiation, days to 100% flowering, panicle length, flag leaf length, days to maturity, number of fertile spikelet/panicle, number of effective tillers/hill, grain yield/10-hill, and 1000-grain weight. In general the hybrids performed significantly better than the respective parents. Significant heterosis was observed for most of the studied characters. Among the 10 hybrids, four hybrids viz., 17Ax45R, 25Ax37R, 27Ax39R, 31Ax47R, and 35Ax47R showed highest heterosis in 10-hill grain yield/10-hill. Inbreeding depression of F2 progeny was also studied for 11 characters of 10 hybrids. Both positive and negative inbreeding depression were found in many crosses for the studied characters, but none was found significant. Selection of good parents was found to be the most important for developing high yielding hybrid rice varieties.     

Characterization and mapping of a lesion mimic mutant in rice （Oryza sativa L.）

A rice initiation-type lesion mimic mutant (lmi) was identified, which was isolated from an indica rice Zhongxian 3037 through γ radiation mutagenesis. Trypan blue staining and sterile culture revealed that the mutant spontaneously developed lesions on the leaves in a developmentally regulated and light-dependent manner. Genetic analysis indicated that the lesion mimic trait was controlled by a single resessive locus. Using public molecular markers and an F2 population derived from lmi and 93-11, we mapped the lmi locus to the short arm of chromosome 8, nearby the centromere, between two SSR markers RM547 and RM331. The genetic distance was 1.2 and 3.2 cM, respectively. Then according to the public rice genomic sequence between the two SSR markers, lmi was further finely tagged by three CAPS markers: C4135-8, C4135-9 and C4135-10. And lmi locus was a co-segregated with marker C4135-10, providing a starting point for lmi gene cloning.     

Infection Mechanism of Neovossaia horrida in Male Sterile Lines of Rice （Oryza sativa L. ）

After male sterile rice plants are inoculated with secondary sporidia of Neovossia horrida in the field,the process of infection is comparatively studied in four male sterile rice lines by scanning electmnmi-croscope. The infection process of Neovossia horrida is similar in these four male sterile lines. The results show, that the hyphae of fungus penetrates directly to the stigma, and then to the ovary after inoculation for 8h. The initial teliospore is formed between the aleurone layer and seed coat after 7d and matured in 9d. Although fungus penetrates through stigma without pollination, teliospore occurs only in the healthy developing endosperma.     

Genetic analysis and gene mapping of leafy head （lhd）, a mutant blocking the differen-tiation of rachis branches in rice （Oryza sativa L.）

Flowers, fruits and seeds are products of plant re- productive development and provide the important sources of foods for humans. Therefore, the moleculargenetic mechanisms of floral development have been ahotspot of research of plant developmental biology[1]. Rice is one of the most important staple food crops. Theoutcome of its reproductive development would determine the yield and quality of grains. Rice is also a model plantof cereals. Hence, the study of rice reproductivedevelopment, esp…     

Genetic analysis and fine mapping of an enclosed panicle mutant esp2 in rice （Oryza sativa L.）

The phenomenon of panicle enclosure in rice is mainly caused by the shortening of uppermost internode.Elucidating the molecular mechanism of panicle enclosure will be helpful for solving the problem of panicle enclosure in male sterile lines and creating new germplasms in rice.We acquired a monogenic recessive enclosed panicle mutant,named as esp2 (enclosed shorter panicle 2),from the tissue culture progeny of indica rice cultivar Minghui-86.In the mutant,panicles were entirely enclosed by flag leaf sheaths and the uppermost internode was almost completely degenerated,but the other internodes did not have obvious changes in length.Genetic analysis indicated that the mutant phenotype was controlled by a recessive gene,which could be steadily inherited and was not affected by genetic background.Apparently,ESP2 is a key gene for the development of uppermost internode in rice.Using an F 2 population of a cross between esp2 and a japonica rice cultivar Xiushui-13 as well as SSR and InDel markers,we fine mapped ESP2 to a 14-kb region on the end of the short arm of chromosome 1.According to the rice genome sequence annotation,only one intact gene exists in this region,namely,a putative phosphatidylserine synthase gene.Sequencing analysis on the mutant and the wild type indicated that this gene was inserted by a 5287-bp retrotransposon sequence.Hence,we took this gene as a candidate of ESP2.The results of this study will facilitate the cloning and functional analysis of ESP2 gene.     

Molecular evolution of rice S 5 n and functional comparison among different sequences

The wide compatibility gene, S ₅ ⁿ , can overcome embryo sac sterility between indica and japonica subspecies of rice. Therefore, it is very important to characterize the features of the S ₅ ⁿ sequence to reveal the origin and evolution of S ₅ ⁿ . In this paper, 26 cultivated rice haplotypes and 22 wild rice accessions harboring S ₅ ⁿ were used to sequence S ₅ ⁿ . The results showed that 15 genotypes among the 48 materials were fully consistent with control cultivar 02428 (CK). The other 33 accessions had different degrees of variation in the S ₅ ⁿ sequence. Variations in the coding region mainly occurred in the second exon and eight materials showed a 10-bp deletion at 1710?C1719 bp, including wild (O. nivara) and cultivated rice, such as IRW501 and Yuetai B. S ₅ ⁿ sequences were not biased and evolved neutrally. The 48 materials could be divided into 4 categories using a phylogenetic tree of the amino acid sequences. Most of the wild rice clustered together, and the cultivated rice clustered into another group. Eight cultivated rice and O. nivara (wild rice) clustered in another group, which were found to lack 10 consecutive bases in exon 2. Eight rice varieties with high numbers of differences in their S ₅ ⁿ coding regions were crossed with testers (typically indica and japonica) to produced test cross F₁ populations. The F₁s were examined for their ability to overcome indica-japonica hybrid sterility. The result showed that the embryo sac fertility of S ₅ ⁿ -containing hybrids increased significantly compared with control hybrids, but there were no differences among the materials with divergent sequences, indirectly proving that S ₅ ⁿ is a non-functional gene.     

亚洲栽培稻5种不同生态类型与籼粳间的杂种F1育性研究

为全面系统地研究亚洲栽培稻种内不同生态类型材料与籼、粳亚种杂交育性,对19份包含亚洲栽培稻种内5种不同生态类型品种与云南温带粳品种滇粳优1号及国际水稻所选育的籼稻品种IR64的杂种F₁育性进行分析. 结果表明,亚洲栽培稻不同类型中,温带粳与籼亚种间普遍存在杂种不育,温带粳与热带粳间、籼籼部分组合也存在杂种不育,Aus类型与籼、粳亚种的杂种不育程度与品种相关. 研究结果为系统研究亚洲栽培稻不同生态类型与籼、粳间杂种不育奠定了基础,为认识亚洲栽培稻的分化提供证据,并为利用亚洲栽培稻种内丰富的遗传变异来培育新品种、新组合提供理论指导.     

Genetic analysis and fine mapping of a lax mutant in rice

We have analyzed a lax mutant that exhibits altered panicle architecture in rice.The primary and secondary rachis-branches are normally initiated and each branch ends in a terminal spikelet,but all the lateral spikelets are absent and the terminal spikelet displays variegated structures in the mutant.An F2 population from the cross between the lax mutant and a japonica variety,W11,was constructed and analyzed.Using microsatellite and CAPS markers,the lax locus was mapped on the long arm of chromosome 1,co-segregated with a CAPS marker,LZ1,within an interval of 0.28 cM between a CAPS marker,HB2,and a microsatellite marker,MRG4389.RT-PCR analysis revealed that the expressions of the rice B-function MADS-box genes OsMADS2,OsMADS4,OsMADS16 and OsMADS3 were significantly reduced,whereas the expression of the rice A-function gene RAPIA was not altered.     

水稻光敏核不育突变体与其原种的比较研究

本文对水稻光敏核不育突变体农垦５８Ｓ与其原种农垦５８进行了比较研究。结果表明,光敏核不育突变体农垦５８Ｓ与其原种农垦５８在各个生育期都存在明显的差异。农垦５８Ｓ表现出苗期株高、根长、叶绿素含量比农垦５８显著提高;生殖生长期,农垦５８Ｓ对光周期反应敏感,冠层叶片长度、株高、茎杆重和结实率在长日照或短日照处理下存在显著差异,农垦５８在生殖生长期对光周期反应不敏感。根据以上实验结果和已有的文献报道得出结论：水稻光敏核不育突变体农垦５８Ｓ不仅仅是雄性育性受育性转换期光周期调控这一个性状的突变,而且是同时伴随着多种性状的突变。