| As a major food of the world, rice has been domesticated more than 10000 years by human being. Germplasm resources play an important role in crop breeding as innovative cultivars were always bred successfully by using favorable alleles that discovered in the germplasm. Several cloned genes have revealed important roles in building rice plant structure and/or increasing yield productivity. Genetic diversity and new allele mining of favorable genes in rice germplasm are of very significance for rice molecular breeding. Two hundred eighty-seven accessions, including the mini-core collection of 213 landraces, varieties and elite parents of hybrid rice,46 African cultivated rice (O. glaberrima), and 28 AA-genome wild rice accessions(O. rufipogon, O. nivara, O. barthii and O. meridionalis), were used for allelic diversity analysis and allele mining. The objectives of this study are:to investigate the agronomic characters, of the collection and construct a database of the germplasm collection; analyze gene diversity in the rice mini core collection, subspecies, and wild ancestor; discovery favorable alleles by association mapping. The main results are as follows:1. Fifteen important agronomic characters of the collection were investigated in 4 environments according to the "rice germplasm describe criterion and data standard". A database was constructed base on the phenotypic dataand can be searched in intra-network.2. The mini-core collection holds abundant diversity of agronomic characters with average CV range from 0.14 to 0.48. There are significant correlation coefficients between different agronomic characters. Notably, the SPAD value has close relationship with 10 agronomic characters.3. A set of 24 unlinked SSR markers from 12 chromosomes were used to analysis population structure. Based on model-based estimation of the 24 SSR markers, the germplasm population showed a predominant structure with two subpopulations in correspondence with indica and japonica subspecies.4. We discovered three polymorphic loci in starch biosynthesis genes RSs3,SDE-Iso and SDE-pu. The three markers together with 4 markers targeted to the other starch biosynthesis genes were used to assess diversities in a panel of rice germplasm which included the 213 Chinese mini core collections,6 African cultivated rice (O. glaberrima), and 29 AA-genome wild rice accessions (O. rufipogon, O. nivara, O. barthii and O. meridionalis). Genealogy treesshowed that there is a distinct divergence between indica and japonica. Furthermore, wild rice has new alleles in the 6 starch biosynthesis related genes, and the O. glaberrima has a set of unique alleles in the starch biosynthesis pathway distinct from that in O. sativa.5. Two novel polymorphic loci, RGS1 and RGS2, were discovered in the last intron and the final exon of GS3, respectively. Together with other two polymorphic loci SF28 and SR17, a number of alleles at these four polymorphic loci were observed in a total of 287 accessions including the mini core collection, African rice and AA-genome wild relatives. Association mapping showed that polymorphic loci SF28, RGS1 and RGS2 were all highly associated with rice grain, and explained a large propotion of the variation. The genic marker RGS1 based on the motifs (AT)n was further validated as a functional marker using two sets of backcross recombinant inbred lines.
|
PDF Full Text Request