Genetic and physical fine-mapping of the Sc locus conferring indica-japonica hybrid sterility in rice (Oryza saliva L.)

摘要

Hybrid sterility is a major hindrance to utilizing the heterosis in indica-japonica hybrids. To isolate a gene Sc conferring the hybrid sterility, the locus was mapped using molecular markers and an F_2 population derived from a cross between near isogenic lines. A primary linkage analysis showed that Sc was linked closely with 4 markers on chromosome 3, on which the genetic distance between a marker RG227 and Sc was 0.07 cM. Chromosome walking with a rice TAC genomic library was carried out using RG227 as a starting probe, and a contig of ca. 320 kb covering the Sc locus was constructed. Two TAC clones, M45E14 and M90J01 that might cover the Sc locus, were partially se-quenced. By searching the rice sequence databases with sequences of the TACs andRG227 a japonica rice BAC sequence, OSJNBb0078P24 was identified. By comparing the TAC and BAC sequences, six new PCR-based markers were developed. With these markers the Sc locus was further mapped to a region of 46 kb. The results suggest that the BACOSJNBb0078P24 and TAC M45E14 contain the Sc gene. Six ORFs were predicted in the focused 46-kb region.