Study On Genetic Diversity Of Upland Rice Resources

Rice is one of the most important food crops in China. The increasing shortage of water resources has been threatening severely to rice production. Upland rice, with strong ability of drought resistance, can adapt the environment of water-deficient. Recent years, the investigative hot-point has been forming in exploring the rice germplasm with drought resistance, advancing the ability of drought resistance of rice, and researching the mechanism of drought resistance of rice. This study focuses on the genetic diversity of upland rice based on 11 morphological traits and 38 SSR primers by conducting the experiments using 144 upland rice varieties which are coming from 4 different geographic regions (including Africa, South America, Asian countries and China). The results are found as follows:1. The analysis of drought resistance indicated that 38.3% of materials tested were identified to have strong drought resistance were identified from the upland rice germplasm tested, revealing more materials with drought resistant materials in upland rice. There existed differences in drought resistance in different rice growing stages. About 27.7% of the materials which showed poor tolerance to drought in seedling stage were discovered to have good drought tolerance in planting recovered stage. Thus it was better to adopt the recovered method to evaluate drought tolerance in vegetative stage.2. The descriptive statistical computations showed that the values of variances of all traits in the experiment are very high, and the coefficients of variation (CV) range from 9.5% to 33.3%, at 11 phenotypic characters. The genetic diversity indices (I) of 11 phenotypic characters range from 1.747 to 2.075, with the average value of 1.990. Among 4 geographic sources, Asia had highest genetic diversity. While that of indica rice is 1.967 which is almost the same as 1.958 of the japonica rice, with no significant.3. A total of 137 alleles were detected by 38 SSR primers from 144 upland rice varieties tested, ranging from 2 to 9 with the average of 3.605 alleles per primer. Polymorphic information content (PIC) ranged from 0.440 to 0.854 with the average of 0.599. The genetic distance and genetic similarity ranged from 0.0822 to 3.6376 and from 0.0263 to 0.9211, respectively. The Nei's gene diversity indices (He) ranged from 0.121 to 0.854, with the average of 0.598. The He (0.558) of indica rice was higher than that(0.415) of japonica one, with the significant at 0.01 level. The allele number (Na) and the He in Asia countries was highest among 4 geographies regions. Therefore, the gene diversity of indica upland rice was more exuberance than that of japonica one.4. The analysis of molecular variance (AMOVA) showed that 76.3% and 23.7% of total genetic variation was existed within subspecies and between subspecies respectively, with significant at 0.01 level. On the other hand, 97.2% and 2.8%of total genetic variation was existed within geographic regions and among geographic ones, with significant at 0.01 level, showing the most genetic variation of upland rice was came from within subspecies and geographic regions. 5. Based on Euclidean distance of 12 morphologic characters, the cluster analysis showed that the materials could divide into 5 groups, but indica and japonica subspecies as well as geographic regions could not clearly identified from the groups. Based on Nei's genetic distance using 38 SSR primers data, 144 upland rice materials could be identified into two types: indica and japonica, which was consistency with the classifying method on the basis of 6 morphological characters. But the SSR method could not classify geographical regions.To sum up, upland rice germplasm is a gene pool having many varieties with strong drought resistance, showing its prolific genetic diversity. Indica upland rice had higher genetic diversity than that of japonica one. There existed greater genetic differences in upland rice among 4 geographic regions. The above results could provide a strong material base for saving water consumption in upland rice breeding, rice production and genetic study. The recovered method setting up by the present study has proved that it was a satisfied way to evaluate drought resistance in rice vegetative growth stage. This method could apply for screening materials with drought resistance in large-scale, judging drought resistance for populations of gene localization, as well evaluating rice drought resistant level of varieties and lines, which showed its important application value.