Development And Characterization Of Substitution Lines From A Cross Of Oryza Sativa And Oryza Minuta

Cultivated rice (Oryza sativa L.) is one of the most important crops in the world. The wild species are rich in extremely valuable genes and genetic diversity. To search beneficial genes from wild rice which have been lost or weakened in cultivated rice is one of the important researches on rice resources and breeding. In this study, an substitution lines populations derived from Oryza minuta (Acc. No. 101133), was rich in resistant gene sources, such as resistance to blast blight, bacterial blight (BB), whitebacked planthopper, and brown planthopper, as a donor, and an indica cultivar IR24 (Oryza sativa L.), developed by International Rice Research Institute, which had high yield and good quality, as a recipient, was used to identify quantitative trait loci (QTL) associated with 9 yield and its components traits and 3 grain type traits using advanced backcross QTL analysis (AB-QTL). At the same time, we report the characterization of the interspecific hybrids and the backcross progenies, and a new bacterial blight resistance gene from O. minuta genetic analysis and mapping. The main results were as follows:1. Interspecific hybrids were obtained from the cross of O. sativa L. (IR24) and O. minuta (Acc. No. 101133) with 5.58% crossability, which was 0.11%, 0.37% and 1.62% in the BC₁, BC₂, BC₃ generations, respectively. The chromosome numbers of interspecific hybrid was 36, and that of the backcross progenies were 24 to 48.2. A total of 175 pairs of SSR primers distributed over all 12 chromosomes of cultivated rice, were used to amplify genomic DNA samples prepared from cultivated rice IR24 and wild rice O. minuta (Acc. No. 101133). Simple sequence repeat markers analysis showed that the polymorphism ratio of SSR bands between IR24 and O. minuta (Acc. No. 101133) was 93.2%. The average donor segment number, length, donor genome size, and percentage of donor genome of 92 BC3F1 plants (2n=24) were 24.1, 17.8 cM, 438.4 cM and 26.2, respectively.3. After inoculation with eight Xoo strains, O. minuta (Acc. No. 101133) showed high resistance to all eight Xoo strains (lesion lengths less than 1.0 cm), while IR24 was susceptible to all eight Xoo strains. The F₁ plants were resistant to all eight Xoo strains, while amongst 56 BQ plants, differential reaction to differential Xoo strain was observed. The resistance of BC₁ plants was segregated. 4. Based on the genotypes of BC₄F₁ population and the investigation of 12 traits of BC₄F₂, quantitative trait loci (QTL) associated with 12 traits were detected using AB-QTL analysis. For 9 yield and its components traits, 28 and 31 QTLs were detected in Wuchang and Hainan, positive alleles from O. minuta (Acc. No. 101133) were 46.4% and 48.4%, respectively. For 3 grain type traits, 12 QTLs were detected in Wuchang, 5 favorable QTL derived from O. minuta (Acc. No. 101133).5. Using a BC₂F₂ populations and its F₃, F₄ families, we discovered a new bacterial blight resistance gene derived from Oryza minuta (Acc. No. 101133) through genetic analysis and identification of anti-spectrum, and designated as Xa31(t). Using SSR marker, the Xa31(t) locus was mapped to a region of about 1.76 cM. This locus co-segregated with marker RM144 and was 0.66 cM from marker RM6293 on one side and 1.1 cM from marker RM7654 on the other side, in rice chromosome 11.