A new gene controlling sterility in F1 hybrids of two cultivated rice species

The interspecific F1 hybrid between the two cultivated rice species, Oryza sativa L. and O. glaberrima Steud., is male sterile but female fertile. To extract and examine elements causing F1 pollen sterility, a backcross experiment was carried out. The sativa (Taichung 65) and glaberrima (W025) parents were considered to be Sa3/Sa3 and S3/S3, respectively. The S3 locus had no deleterious effect on the development of microspores in the homozygote but induced abortion of pollen not carrying It in the heterozygote S3/Sa3 There appears to be no adverse effect of S3 on megaspores or somatic cells, which differs in genic action from the S1 and S2 alleles reported previously. The Sa3 locus was tightly linked with la (lazy habit) on chromosome 9. In addition, plants homozygous for S3 proved to be photoperiod sensitive and showed the heading date about 10 days later than those having S3/Sa3 or Sa3/Sa3 in the summer seasons. Frequently observed sterility genes of gametophytic type In rice are discussed in relation to their origin.