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-5^j while the Indica tester has S-5ⁱ at the S-5 locus belonging to linkage group I, and that female gamates with S-5^j are aborted in plants with the genotype of S-5ⁱ/S-5^j. 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.