Molecular Marker-based Genetic Analysis Of Some Important Traits For Improvement Of Shanyou 63, An Elite Rice Hybrid

We took shanyon 63(Zhenshan 97/Minghui 63), an elite rice hybrid of China, as material to carrt out this study to discuss the genetic basis for improvement of its quality and bacterial blight resistance(Xanthomonas oryzae pv. oryzae). The main results are as follows: 1). Two kinds of DNA-bascd markers SSR and RAMP were analyzed and used inthe diversity evaluation and genome mapping. The detected polymorphisms were quite similar for the two kinds of markers. In a single PCR reaction RAMP could detect more bands than SSR could. No allclism was detected among the amplified bands of the RAMP, and the mapped bands appeared to be dominant markers. By surveying the selected accessions covering indica, japonica and O. nifipvgon the order of the detected allclcs(or bands) and the PIC by SSR or RAMP was indica>japonica>O. nifipogon. indicating the diversity in the inclica rice arc higher than the other two subspecies. With 11 SSR markers the selected 46 accessions could be clustered into three subgroups, supporting the "two-line evolution" hypothesis. Similar result could be drown with the RAMP. These results implied that the simple repeat sequence was changed coordinately with the evolution of the rice genome, and both SSR and RAMP could be useful for germplasm evaluation and utilization.Thirty SSR and RAMP markers were integrated into the constructed RFLP linkage map without any biased distribution in the genome. Some of the markers were just filled up the linkage gaps of some chromosome, or mapped into the centremeres.2). Inoculated with different Xoo strains by testing the F₂,3 families and the RIL population derived from the same cross, an dominant R gene was detected in Minghui 63. With the RFLP linkage map the gene was verified to be Xa and was finely mapped on the top. of chromosome 11 where clustered several resistance genes.3). The Wx gene was also mapped and evaluated in rice quality determination. By analyzing 75 representative cultivars of different quality it was found that amylose content(AC), gel consisteney(GC) and gelatinization temperature(GT expressed byASV, alkali spread valuc)were highly correlated with cach other. All the parents of three line rice hybrid except Minghui 63 were with very high AC, hard GC and low GT, and similar situation was found for some famous high yielding landraces which were all with low quality to have been climinated through selection: whereas the quality rices were with intermediate to low AC, soft GC and intermediate to low GT. Too high AC was the major cause for low palatability grade. To improve the quality of hybrid rices should begin with reducing the AC of the parents.' Another finding was that two SSR motifs as (CT) and (AATT) located near the transcription of the Wx gene were correlated with each other and related to AC of the grain. Eight allcles were found with the (CT)n repeat. Those varieties with n>14 were all with lower AC whereas those with n≤14 were all with very high AC. The waxy rice could not be distinguished from the low AC verities by the (CT) repeat indicating other genetics was involved in the AC for waxy rices. Combined with the RFLP data of the F_<sub>2:3 and RIL populations the AC. GC and GT were all determined by the Wx gene region, which was confirmed by QTL scanning . With the fine map of the corresponding region a system suitable for marker-assisted selection against the Wx gene was set up.4). Analysis was carried out to delect the QTLs for the quality characters with the linkage map. The traits of the paddy grain and the brown rice grain were highly-correlated and the corresponding QTL involved were approximately the same. The grain length was mainly controlled by the inten'al of chromosome 3, with the explained phenotype variation of more than 40% by the QTL. The grain width was affected by the two adjacent QTLs located on chromosome 5 with each explaining 20% of the phenotype variance. The QTL affecting grain shape was not detect...