Edects ofRit 1 , Rit 3 and Rif 6 ( D Genes on Fertility Restoration in Rice ( 0 i : yza sativa L . ) with WA - and BT - type Cytoplasmic Male Sterility

Genes involved in the fenility restoration (llf) ofwild-abortive (WA)-type cytoplasmic male sterility (CMS) in rice have not been clearly identified, because of the inconsistency of their number and map position, Although the IILI genes, which restore Chinsurah Boro (BT)-type CMS, have been recently isolated, their efi fects on WA-type CMS are still unclear, In the present study, near-isogenic lines (NILs) ofJ'oponica rice, differing at ilf' leci, were developed using marker-assisted selection (MAS) to determine the effect of each llf'gene on WAor BT-cytoplasm in aJ'aponica background. The NILs were crossed with aJ'aponica CMS line, then the pollen and seed fertility of he hybrid plants was analyzed. The IIAI locus consisting oftwo Rf'genes from IR36 was suencient to restore fertility n the hybrids with BT-type CMS but conferred very little f rtility to those with WA-type CMS. IIL3 on chromosome 1, a weak Rf'gene, and Rl16(Z) on chromosome 10 were unable to confer seed fertility to plants with BT-type or WA-type CMS, Both fYgenes, however, could accelate the development of abortive pollen in the case of WA-type CMS and their effect was additive. Crossing of CMS rice with chromosome segment substitution lines carrying i!floci from IR24 resulted in similar pollen development and seed fertility.