Construction Of A High-density Molecular Linkage Map Of Rice And Mapping Of QTLs For Storage-tolerance Of Seeds

Based on a population of recombinant inbred (RI) lines derived from a cross between two indica rice varieties, H359 and Acc8558, a high-density molecular marker linkage map was constructed by integrating SSR markers into an existing map consisting of RFLP and AFLP markers.The parents were surveyed for DNA polymorphisms using 509 pairs of published SSR primers. 331 pairs of the primers revealed polymorphisms between the two parents, and 79 pairs of them were selected for genotyping the RI lines. With the obtained genotype data of SSR markers and the previous data of RFLP and AFLP markers, a new molecular map was constructed, which contains 306 markers (including 147 RFLPs, 78 AFLPs and 81 SSRs) and covers a total length of 1987.5cM with an average distance of 6.5cM between adjacent loci. The SSR markers are evenly distributed over all chromosomes. In this map, the RFLP probes are from the map constructed by the Japanese Rice Genome Program, while the SSR primers are from the maps constructed by Cornell University. So, this map can serve as a bridge for the cross-reference of genetic information between the two maps.With the RI population and the new map, mapping of QTLs for the storage-tolerance of rice seeds was conducted. Seeds of each line were treated for one week and two weeks, respectively, for speeding up seed aging under the condition of 40癈 and over 90% RH. Untreated seeds were used as the control. The germinating ability (including germination percentage, germinating potential and germination index) and paste viscosity (including the three parameters of RVA profile: peak viscosity, hot paste viscosity and cool paste viscosity) of seeds were investigated. The relative alteration of each trait after the aging processing treatment [= (treatment-control)/control] was used as an index of seed storage-tolerance. Principal component analysis was performed with all indexes of the two treatments and two largest components, the storage-tolerance of seed vigor (the first principal component) and thestorage-torlance of grain quality (the second principal component), were obtained, which could explain 76.46% of the variation. QTL mapping was conducted with the two principal components, respectively. Seven QTLs for the storage-tolerance of seed vigor were detected, which could explain 32.49% of total phenotypic variation; 14 QTLs for the storage-tolerance of grain quality were detected, which could explain 58.48% of total phenotypic variation. The positions of two QTLs (qSVSS and qSVST) underlying the storage-tolerance of seed vigor are close to the reported QTLs for seed dormancy, implying that seed dormancy might be reletive to seed storage-tolerance in rice.