Multiple alleles controlling F1 sterility in remote crosses of rice (Oryza sativa).

Abstract

We reported previously that Indonesian rice varieties belonging to the so-called Javanica varieties could be classified into some different types in respect to F1-sterility relationships with a set of Indica and Japonica testers. Firstly, in this study, we observed that the F1 Plants between these different types were fertile with a few exceptions. Secondly, to look into the genetic basis of the sterility of the F1 hybrids between a variety, Penuh Baru II and Indica or Japonica testers, we made threevarietal crosses involving Penuh Baru II, a “wide-compatibility” variety Ketan Nangka, and IR 36 or IR 50 (Indica tester). The progeny of the three-varietal crosses showed an association of spikelet fertility with certain gene markers. The segregation pattern for the spikelet fertility was explained by a model of one-locus allelic interaction. It was postulated that the Japonica tester as well as Penuh Baru II have the same allele S-5j while the Indica tester has S-5i at the S-5 locus belonging to linkage group I, and that female gamates with S-5j are aborted in plants with the genotype of S-5i/S-5j. Ketan Nangka was found to have a wide-compatibility allele S-5n which does not confer sterility in combination with other alleles. The F1 sterility of Penuh Baru II with Japonica tester appeared to be controlled by sterility genes other than those at S-5 locus. The wide-compatibility gene S-5n can be usefull in the breedig of Indica-Japonica crosses and also in developing Indica-Japonica F1 varieties.