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Genetic Diversity Detected with RFLP Markers among Rice Cultivars (Oryza Sativa L.) and Its Utilizaton in Hybrid Rice Breeding

Zhang Peijiang et al (Anhui Academy of Agricultural Sciences, Key Laboratory of Rice Genetics & Breeding Ministry of Agricultural, The P. R. China, Hefei 230031)  
Seveteen parents of hybrid rice and 3 new plant type lines and 24 Nuda, Javanica cultivars were used to evaluate genetic diversities by RFLP markers between parents. The possibility was explored that genetic diversity estimated from RFLP banding patterns was used in hybrid rice breeding. Results indicated that Forty-two probes using in this study generated 69 different restriction fragments in the 44 varieties. Twenty (47.6%) probes detected 47 (68.1%) polymorphic fragments that were different at least between two parents. Each of those polymorphic fragments were scored 1 for present and 0 for absent. Based on the pair-wise comparisons of restriction fragments the genetic distance was calculated using Nei's genetic distance and a dendrogram was constructed using an unweighted pair group method with arithmetical averages (UPGMA). The indica and japonica cultivars were easily classified into separate groups by cluster analysis, and temperate and tropical japonica cultivars were classified into separate subgroups, too. But Nuda and javanica cultivars were usually clustered in mixed subgroup. In general, a higher level of polymorphism was found between japonica and indica subspecies while fewer polymorphisms were found between Nuda and javanica cultivars within the japonica subspecies, and the genetic distance between temperate japonica and Nuda was further than the genetic distance between temperate japonica and javanica. The results from the dendrogram were found that the economical heterosis between temperate japonica cultivars was low, the heterosis between subgroups was stronger and the heterosis between groups (indica / japonica) was strongest. Making use of Nuda and javanica, parents of hybrid rice as distinct from ecotype were bred, and high-yield hybrid rice combinations had been bred.
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