Mining Of Elite Alleles For Outcrossing-Related Traits In Rice(Oryza Sativa L.)

The area of hybrid indica rice (Oryza sativa L.) planted annually is over16000000ha and accounts for about52%of total rice area in china. The yield of hybrid rice accounts for about66%of total rice yield. The area of japonica rice planted annually is8280000ha and accounts for27%of total rice area in china. The area planting japonica hybrid rice is only3%of the total area of japonica rice. The major reasons for this situation are that comparatively weak heterosis and the low yield of F1seed production in japonica hybrid rice. The key factor of enhancing seed-producing yield of japonica hybrid rice is to improve its outcrossing characteristic, which affected directly the rate of outcrossing in seed production field. If the percentage of exerted stigma of sterile line is high, and the rate of female’s and male’s blooming period and blooming time is increased, then seed production will achieve the high yield and stable yield. Therefore, In order to provide reference for breeding sterile line and high seed production, it is necessary to study systematically outcrossing habit in riceA natural population composed of ninety five rice varieties from the rice core germplasm in Taihu lake region was used for test materials, This paper conducted the following studies:A natural population was phenotyped for the6traits(flag leaf angle, filament length, anther length, stigma length, percentage of exerted stigma and angle of glumes opening) in paddy rice field and genotyped with93SSR molecular markers contributed on12chromosomes, so as to describe population genetic characteristics, including genetic diversity, population structure and linkage disequilibrium. Association between the markers and the six traits was analyzed by using general linear model (GLM) in software of Trait Analysis by aSSociation, Evoluation and Linkage (TASSEL). A set of elite alleles and their carrier varieties with large phenotypic effect were detected. and then identify elite lines through SSR genotypic information, the aim is to provide parents materials for rice breeding. Meanwhile, it can also provide reference for discovering gene germplasm and innovation research. The results obtained were as follows:(1) In natural population, PES had the largest variation (CV=62.9%), followed by FLA (CV=50.2%), and FL had the smallest variation (CV=9.9%) amomg the six outcrossing traits, indicating that improving potential of the two traits, PES and FLA, was greater than that of the other four traits investigated in natural population.(2) In the genetic diversity analysis,93SSR molecular markers generated a total of430alleles in the ninety five rice varieties. The average number of alleles per locus is5, ranged from2to11. The average gene diversity is0.593, ranged from0.021to0.866. and the average PIC per locus is0.529, ranged from0.021to0.851, indicating that natural population used in this study have an abundant genetic diversity.(3) The natural population was divided into10sub-populations by means of the STRUCTURE. To futher analyze biology significance of the number of sub-population, finding that sub-population division of natural population was associated with tassel period. Indicating that differentiation in genetic is related to the division ecotype.(4) Variable LD was detected not only among markers on the same chromosome but also different ones. Of the4278pairwise loci in LD,1334loci pairs (～31.2%) were significant (p<0.01) in landrace population, and354loci pairs (～8.27%) were significant in released cultivar population. The distribution of D’value and its average value in population of released cultivars was higher and more extensive than those in population of landrace, artificial selection increase the degree of LD.(5) In total47SSR marker loci associated with the6traits were detected. Among them,11with flag leaf angle (FLA),9with filament length (FL),34with anther length (AL),10with stigma length (SL),12with percentage of exerted stigma (PES) and3with angle of glumes opening (AGO).(6) A set of elite alleles and their carrier varieties with large phenotypic effect were detected. RM450-138bp band in variety Wumang zaodao had the largest effect in increasing FLA, FL and AL. RM336-145b band in Xianhui429had the largest effect in increasing SL. RM234-143bp band in Nannongjing62401had the largest effect in increasing PES. RM257-189bp band in C-bao had the largest effect in increasing AGO.