Seminar

Title：Genomic diversity and introgression in O. sativa reveal the impact of domestication and breeding on the rice genome.

Reporter: Keyan Zhao

 　　　　　　  Cornell University, Ithaca, NY, USA

Host: Weiwei Zhai

Time：3:00 pm.-4:00 pm. On Nov.10, 2009

Location：Conference room 202, Beijing Institute of Genomics，CAS

Abstract:

The domestication of Asian rice (Oryza sativa) was a complex process punctuated by numerous episodes of introgressive hybridization among and between different subpopulations and varietal groups. Deep genetic divergence between the two main varietal groups (Indica and Japonica) suggests domestication from at least two distinct wild populations. However, genetic uniformity surrounding key domestication genes across divergent subpopulations suggests cultural exchange of genetic material among ancient farmers.  In this study, we utilize a novel SNP panel genotyped across 395 diverse accessions of O. sativa to study genome-wide patterns of polymorphism, to characterize population structure, and to infer the introgression history of domesticated Asian rice. Our population structure analyses support the existence of five major subpopulations (indica, aus, tropical japonica, temperate japonica and aromatic/GroupV) consistent with previous analyses.  Our introgression analysis shows that most accessions exhibit some degree of admixture, with many individuals within a population sharing the same introgressed segment due to artificial selection. Genes in these regions control a myriad of traits including plant stature, blast resistance, and amylose content.  Admixture mapping and association analysis of amylose content and grain length illustrate the potential for dissecting the genetic basis of complex traits in domesticated plant populations. The deep population structure also imposes challenges for approximate statistical methods in this kind of mapping populations. These analyses highlight the power of population genomics in agricultural systems to identify functionally important regions of the genome and to decipher the role of human-directed breeding in refashioning the genomes of a domesticated species.

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