Marker-assisted selection and evaluation of the QTL for stigma exsertion under japonica rice genetic background.

Stigma exsertion is one of the important traits which contribute to the efficient improvement of commercial seed production in hybrid rice. In order to understand the genetic factors involved in the stigma exsertion of an indica variety--IR24--a QTL analysis was conducted using the F2 population between a japonica variety--Koshihikari--and a breeding line showing exserted stigma selected from the backcross population between IR24 as a donor and japonica varieties. As a result, a highly significant QTL (qES3), which had been predicted in the recombinant inbred population of IR24, was confirmed at the centromeric region on chromosome 3. qES3 increases about 20% of the frequency of the exserted stigmas at the IR24 allele and explains about 32% of the total phenotypic variance. A QTL near-isogenic line for qES3 increased the frequency of the exserted stigma by 36% compared to that of Koshihikari in a field evaluation, which suggests that qES3 is a promising QTL for the development of a maternal line for hybrid rice.