Evaluation of genetic diversity of rice landraces (Oryza sativa L.) in Yunnan, China

Genetic diversity and geographic distribution of rice landraces in Yunnan, Southwest China were investigated based on 31 morphological traits (including Ding and Cheng's classification traits) using 6,121 accessions, 41 morphological traits and 12 polymorphic isozyme loci within the primary core collection of 912 accessions, and 20 microsatellite markers within the core collection of 692 accessions. Yunnan is the richest center of genetic diversity of rice (O. sativa L.) germplasm in China, in which indica varieties were derived from 108 counties in 16 prefectures and japonica varieties from 99 counties in 17 prefectures. Geographic distribution and diversity of six ecogroups and classification traits displayed clear differences. The average diversity indices of six ecogroups of rice landraces in Yunnan ranked as follows: javanica (1.2319), aman (1.1738), communis (1.1726), nuda (1.1618), aus (1.1371) and boro (0.9889), and the percentages were 3.6%, 43.9%, 32.1%, 18.1%, 2.1% and 0.2%, respectively. Lincang, Simao, Xishuangbanna and Dehong prefectures form the genetic and gene diversity center of rice landraces in Yunnan, especially Lincang Prefecture is not only the main genetic diversity center of rice landraces in Yunnan but also the diversity center of Ding's and Cheng's classification traits. South marginal paddy-upland rice region with Myanmar is the center of the gene diversity of rice landraces in Yunnan. A core collection from Yunnan rice landraces was identified based on morphological, isozyme and DNA variations, which have confirmed that Yunnan is the center of genetic differentiation of indica and japonica subspecies of Asian cultivated rice.