The Effects Of Rf4 And The Genetic Mechanism Behind Fertility Restoration Of Wild Abortive Cytoplasmic Male Sterility (WA-CMS) In Japonica Rice (Oryza Sativa Ssp. Japonica)

Wild abortive-type cytoplasmic male sterility (WA-type CMS) has been exclusively used in hybrid seed production in indica rice cultivars, and fertility restoration in WA-type CMS is controlled by two major restorer genes, Rf3 and Rf4, through a sporophytic mechanism. However, the genetic mechanism underlying fertility restoration in WA-type CMS in japonica cultivars is poorly understood. In the present study, C418, a leading Chinsurah Boro II- (BT)-type japonica restorer line, showed partial restoration ability in WA-type japonica CMS lines. The 1:1 segregation ratio of partially fertile to sterile plants in a three-cross F 1 population indicated that fertility restoration is controlled by one dominant gene. Gene mapping and sequencing results revealed that the target gene should be Rf4 . The Rf4 gene restores fertility through a sporophytic mechanism, but the Rf4 pollen grains show a preferential fertilization in the testcross F 1 plants. Furthermore, Rf4 was confirmed to have only a minor effect on fertility restoration in WA-type japonica CMS lines, and Rf gene dosage effects influenced the fertility restoration of WA-type CMS in japonica rice. The results of our study not only provide valuable insights into the complex genetic mechanisms underlying fertility restoration of WA-type CMS but will also facilitate the efficient utilization of WA-type CMS in japonica rice lines.