Introduction of a xantha mutation for testing and increasing varietal purity in hybrid rice

Abstract

A xantha mutant (yellow plant) was induced by gamma rays irradiation of a cytoplasmic male sterile (CMS) maintainer line II32 B of rice ( Oryza sativa L.). It was identified earlier as a low gelatinization temperature mutant and named as Mgt-1. Through a series of backcrosses of Mgt-1 to CMS line II32 A, a new CMS line was developed and named as Huangyu A (B). Genetic analysis showed that the xantha mutation was controlled by a single recessive locus, and all F 1 plants from crosses of Huangyu A (B) with other normal green varieties showed normal green leaves. The xantha mutation resulted in reduction of photosynthetic pigments content at various levels, e.g., 48% of chlorophyll a (Chl a), 71% of chlorophyll b (Chl b), and 30% of carotenoids (Car), and consequently increased the ratios of Chl a/Chl b and Car/Chl in Huangyu A (B) against II32 A (B). Unexpectedly, Huangyu A (B) had higher photosynthetic rates in comparison with II32 A (B), and so did the F 1 plants of Huangyu A/R3027 as against those of II32 A/R3027. Huangyu A had similar male sterility completeness and stability as II32 A, but the former showed significantly better combining ability than the latter. The yellow color made the seedlings and plants of Huangyu A (B) visually distinguishable from the green ones and thus it was a very distinct marker applicable for rapid testing and efficient increasing varietal purity in seed and paddy production of hybrid rice.