Allelic Relationship and Location of Gene Controlling Short Stature in Thai Wild Rice ‘SPR 82-83’

Abstract

The Thai wild rice, ‘SPR 82-23’, re-identified as Oryza nivara was reciprocally crossed with IR 8 to test the allelic relationship of ‘SPR 82-23’ with Dee-geo-woo-gen derivatives; and as a male parent was crossed with 12 primary trisomic stocks to locate its short stature gene. F1 and F2 Analysis the F1 and F2 generations of the cross between ‘SPR 82-23’ and Dee-geo-woo-gen derivatives showed that the short stature genes of ‘SPR 82-23’ share the same sd1 compound locus but the two parents differed in the ultrastructure of the locus. Differences between parents in the genetic materials adjacent to the sd1 locus could give rise to trans and cis configurations which lead to the appearance of intermediate and tall F2 phenotypes. In the case of IR36/’SPR 82-23’, larger proportions of intermediate and tall F2 plants were obtained. Different genetic backgrounds of the two parents could allow modifying genes (modifiers) in the positive direction (taller heights) to express themselves, although IR36 and ‘SPR 82-23’ also share the sd1 compound locus. The chromosomal location of ‘SPR 82-23’ was determined by trisomic segregation ratios. Due to low F2 population size, conclusive evidence was not obtained on the exact location of the two semi-dwarfing genes. It is probable that the genes might be located in either chromosome 4, 1, 2, 3, 9 or 12. Further studies are needed to confirm the gens system controlling the short stature of ‘SPR 82-23’. Moreover, refined techniques and larger population sizes are needed to pinpoint the exact location of the semi-dwarfing genes in the wild rice.