Heterosis is a heterozygous trait, depending on the genetic diversity of both parents. An approach to tag the heterosis trait with a molecular marker should be different from any other approaches for homozygous traits. To achieve this objective, it is necessary to identify the genetic diversity related to heterosis between both parents. This part of genetic diversity should be closely related to the parental combining ability, which is the most important factor for the performance of the hybrids. Based on the principle of parental combining ability, the simple sequence repeat (SSR) markers favorable and unfavorable to heterosis were identified in the previous study. In the present study, using these markers, two restorer lines with a very high combining ability, MGR44 and MGR45, were developed from the elite restorer line, Minhui63. In these two lines the favorable alleles were maintained while the unfavorable alleles were removed, resulting in the obvious increase of both the general combining ability (GCA) and special combining ability (SCA). Also, the spike density and 1000-grain weight traits were enhanced as compared with Minhui63. These results indicate that the previously selected molecular markers are very useful for hybrid rice breeding programs. Also, it was confirmed that the method described in our previous report is suitable and effective for screening molecular markers for hybrid rice breeding.
2004 by JAPANESE SOCIETY OF BREEDING