Genetic Diversity Analysis Of Currently Cultivated Rice Landraces From Hani’s Terraced Fields In Yunnan Province

Yunnan province is one of the biggest centers of the origin and diversification for Asian cultivated rice. In order to utilize and conserve the currently cultivated rice landraces from Hani’s terraced fields in Yunnan effectively, it is very essential to carry out the studies on genetic diversity, agronomic characters and quality traits of rice landraces. In this study, we analyzed the genetic diversity, population structure, agronomic traits and quality traits of 111 cultivated rice landraces which collected from 10 representative villages of Hani’s terraced fields in 2012-2013. The main results were as follows:(1) The results from analyses of 13 main agronomic and yield characters showed that the currently cultivated rice landraces from Hani’s terraced fields had a higher plant height, the more numbers of tillers and secondary branches, the longer of the sword leaf and the rice grain, the lower of the seed setting rate than that of new released cultivars. Among the main agronomic and yield characters, the variation coefficient of four characters, such as plant height, tiller number, sword leaf length and secondary branch number, was more than 15%, which showed that the currently cultivated rice landraces from Hani’s terraced fields had relative diverse phenotypes. Correlation analysis showed that the grain thickness affected on the seed setting rate and the thousand seed weight in the agronomic and yield characters. Cluster analysis showed us that the materials in this study could be divided into three groups(AⅠ、AⅡ、AⅢ) based on agronomic and yield characters, group AⅠ had a higher plant height, longer ear length and more branches than that of the other groups, and group AⅡ had a lower plant height, the thicker grain thickness and the higher seed setting rate than that of the other groups, and group AⅢ had a longer grain length and the more tillers than that of the other groups. The cultivar number in group AI was the largest, accounting for 90% of the total materials.(2) The main physic-chemical quality characters including appearance amylose content (AAC), gelatinization temperature(GT), gel consistency(GC) and RVA profile were analyzed, and the data showed that most of the currently cultivated rice landraces from Hani’s terraced fields had a high AAC, soft GC. The coefficient of variation of GT was low, but the one of the RVA eigenvalues was high (above 20%). It could be indicated that the currently cultivated rice landraces from Hani’s terraced fields had relative diverse physic-chemical quality characters. The correlation analysis in the main physic-chemical quality characters showed that the AAC and GC have highly significant correlation with other quality characters from the eigenvalues of GT, RVA, which was significant useful value in rice breeding. Cluster analysis showed that the tested materials were divided into non-glutinous rice group (QI) and glutinous rice group (QII). QI was the largest group, accounting for 80.18% of the total materials.(3) Fifty-one SSR markers were used in this study, which showed that there were 123 alleles, ranged from 2 to 4 per locus, with the mean of 2.41, the genetic diversity index varied from 0.15 to 0.54 with an average of 0.34, the polymorphic information content (PIC) changed from 0.14-0.50 with the average of 0.29. The genetic diversity of the currently cultivated rice landraces from Hani’s terraced fields was lower than that of the previous reports. All the landraces could be divided into two groups, i.e the partial indica group (group Ⅰ) and the partial japonica group (group Ⅱ). The group Ⅱ was the largest group, accounting for 83% of the total materials.(4) The allelic variation of two important quality related genes, Wx and ALK, was determined by using gene-specific markers, and the results showed that there was no new allelic locus found. Six and three alleles were detected for Wx and ALK, respectively, which generated 12 combinations within these two genes in this study. AAC, GC and RVA had a rich variation within the same Wx allele; there might be new mutation sites in the Wx locus of the currently cultivated rice landraces from Hani’s terraced fields.(5) The genetic diversity of the landraces was relatively rich, but it had a simplification trend. With the supporting of national policy, evaluation mechanisms of local government management, special rice brand creation and conducting of local rice diversity conservation education would be conducive to the preservation and continuation of rice landraces in Hani’s terraced field.