Search

To specifically improve preharvest sprouting (PHS) and amylose content (AC) in the cytoplasmic male-sterile (CMS) line G46A, two simple sequence repeat (SSR) markers, RM3754 and RM447, that are closely linked to qPSR8, a major quantitative trait locus for PHS, were adopted to select for reduced PHS; SSR marker 484/485, which is tightly linked to the waxy gene, was used to select for AC. In the backcross progenies with G46B, the maintainer of G46A, as recurrent parent and 'Lemont' as donor parent, most plants with a homozygous Lemont allele at both RM3754 and RM447 showed good PHS resistance. Amylose content in the progeny of G46B/Lemont was significantly related to a difference in alleles at the 484/485 locus. Based on agronomic trait performance and evaluation for PHS and AC, 28 elite lines obtained from the BC3F5 generation were then used in further backcross schemes to breed improved CMS lines. Subsequently, two improved CMS lines showed traits similar to G46A but with improved PHS resistance and intermediate AC. [ABSTRACT FROM AUTHOR]

Preharvest sprouting (PHS) is caused by early breaking of seed dormancy. In Sichuan, a major hybrid rice seed production area of China, PHS in hybrid seeds originated from ‘G46A’ parent may lead to severe yield loss, causing serious damage to agricultural production. To detect quantitative trait loci (QTLs) governing PHS, we developed an F2 population of 164 plants derived from ‘G46B’ and ‘K81’, a near-isogenic introgression line of G46B, with high level of resistance to PHS. PHS was evaluated under controlled field and laboratory conditions. Using simple sequence repeat markers, we constructed a linkage map from this population and identified three QTLs for PHS, namely qPSR2, qPSR5 and qPSR8, which were located on chromosomes 2, 5 and 8, respectively. Among these QTLs, qPSR8, residing in the interval between RM447 and RM3754 on chromosome 8, was the major QTL controlling PHS, for it had a relative high logarithm of the odds (LOD) score and explained 43.04% of the phenotypic variation. These results were correspondent to those identified in extreme low germination rate plants (ELGP) using linkage and linkage disequilibrium. At all loci, ‘K81’ was responsible for enhancing the resistance to PHS. [ABSTRACT FROM AUTHOR]