Abstract:

We used field experiments in Hani’s terraced fields in Yuanyang County, Yunnan Province, to compare 23 phenotypic traits of 135 paddy rice landraces, including 66 ones that used to be grown during the 1970s (past-grown landraces) and 69 ones that have been grown during the past decade (current-grown landraces). Comparing 23 phenotypic traits, the average Shannon-Wiener diversity index of the past-grown landraces (H′ = 1.784) was higher than that of the current-grown landraces (H′ = 1.766), while the average coefficients of variation and that of similarity of the past-grown (19.5% and 0.2107, respectively) were lower than those of the current-grown (21.7% and 0.2149, respectively). There were eight and six principal components with eigenvalues > 1 in the past-grown and current-grown landraces, respectively, accounting for 81.4% and 83.2% of their overall variation, respectively. Based on a cluster analysis of the 23 phenotypic traits and a scatter plot of the first three principal components, these landraces could be grouped into two subspecies, indicaand japonica. There was a slightly lower proportion of the indica, waxy, and red pericarp color varieties, as well as strong seed-shattering types in the current-grown landraces than in the past-grown ones. Average plant height, panicle neck length, node length under spike, 1,000-grain weight and flag-leaf angle were all lower in the current-grown. On the other hand, average panicles per plant, flag-leaf width, filled grains per panicle and seed-setting rate increased in the current-grown landraces. In addition, the current-grown landraces had more compact plant types. The simplification and decrease in the genetic diversity of current-grown landraces compared to past-grown landraces may have resulted from the increased use of hybrid rice, selection for high yield traits, and less consideration of the traditional cultural habitude by local ethnic groups. More attention should be paid to both conservation of rice landraces as well as to the traditional rice culture in Yuanyang Hani’s terraced fields in Yunnan Province.

Key words: Oryza sativa, agronomic traits, genetic similarity, principal components, cluster analysis