Epistatic Relationships among Genes Related to Endosperm Starch Synthesis in Rice

The mutants of sugary-2 (su-2), floury (flo), shrunken-1 (shr-1), and dull-1 (du-1) were crossed to waxy (wx) to produce F 2 seeds. Chi-square analysis on the segregating ratio of the F 2 seeds revealed that flo, su-2, and shr-1 were independently transmitted with wx, while wx was epistatic over du-1. The floury and sugary-2 were crossed to Hwasunchalbyeo, a waxy variety, and then the F 4 of floury-waxy and sugary-2-waxy seeds were developed, respectively. As the parents phenotypes of sugary-2 and floury, the grains of these two lines showed lower hardness and grain weight than normal grain of Hwacheongbyeo. For alkali digestive value (AVD), the sugary-2-waxy showed lower ADV than Hwacheongbyeo. For the gel consistency of grain flours, the floury was medium like Hwacheongbyeo, while those of the sugary-2, floury-waxy, and sugary-2-waxy were soft like Hwasunchalbyeo. The amylose contents in the grains of the sugary-2 and floury were decreased to ~15% whereas that of Hwacheongbyeo was 19.1%. All the lines showing waxy endosperm (Hwasunchalbyeo, floury-waxy, and sugary-2-waxy) showed less than 4% amylose contents. Interestingly, the free sugar content in the brown rice was increased to 9.27% in the sugary-2-waxy, showing transgressive segregation phenomenon where the free sugar contents in its parents, sugary-2 and Hwasunchalbyeo, were 5.98% and 3.98% respectively. Also, the floury-waxy showed transgressive segregation phenomenon, containing 6.15% of free sugar content in the grains