Endosperm mutants in rice: gene expression in Japonica and indica backgrounds

Abstract

Dull, sugary, shrunken, floury, white-core, and amylose extender endosperm mutants induced in japonica rice varieties were transferred to IR36, an indica variety, after two backcrosses. Differential pollen staining was used to select heterozygotes among low-amylose (dull) mutants and the high-amylose recurrent parent (IR36). Segregation distortion was observed in some mutants during gene transfer from japonica to IR36. Phenotypic expressions of mutant genes in IR 36 and japonica background were almost similar. However, shrunken-1, which showed partly chalky and partly translucent endosperm in japonica, was completely chalky in indica background. Floury-2 showed variation in phenotype, depending on the degree of distribution of the translucent fraction. Scanning electron photographs showed no starch granules in the endosperm cells of sugary mutants. All the floury-1 and white-core mutants had intermediate amylose (20- 50%) in the IR36 background. Floury-2, on the other hand, produced low amylose in both backgrounds. In general, the amylose content of dull mutants was slightly higher in IR36 background. The amylose extender gene increased the amylose content of IR36 from 25% to as high as 40%, an increase of about 60%.