Identification of segregation-distortion-neutral alleles to improve pollenfertility of indica-japonica hybrids in rice (Oryza sativa L.)

Utilization of the pronounced heterosis of indica-japonica hybrids in rice had been difficult due to panicle sterility caused by male and female gamet e abortion in such hybrids. But the female gamete abortion in the most indi ca-japonica hybrids has been solved by using an abortion-neutral gene S-5(n ) called as wide compatibility gene. On the other hand, the problem of poll en sterility remains to be solved for such hybrids. This study was conducte d to identify abortion-neutral genes for pollen that may be utilized to all eviate pollen sterility in distant crosses. Some cultivars like Ketan Nangk a (KN) and Dular, which are known as wide compatibility variety (WCV), were tested to find whether they possess neutral alleles for segregation distor tion of marker genes. The distorted segregation of markers as well as norma l segregation were confirmed among progeny lines of three-way crosses, WCV/ indica//japonica and japonica//indica/WCV. Neutral alleles for segregation distortion were identified at two gamete gene loci ( ga), i.e., ga-14(t) on chromosome 3 and ga-11 on chromosome 7. A new locus ga-14(t) was identifie d in between Pgi-1 and bc-1 and independent of ga-3 on chromosome 3. The ne utral alleles at the two loci may be used to solve pollen sterility in indi ca-japonica hybrids.