Development of early maturing and semi-dwarf in rice by induced mutations

Crop improvement using classical induced mutagenesis is now well standardized. A large number of new promising varieties in different crops have successfully been developed world wide using both physical and chemical mutagenes. Domsia is one of the best quality and local rice variety in Iran, but it is tall and nearly late in maturity. The dry seeds of this variety were treated with gamma rays at doses 100, 200 and 300 Gy. The irradiated seeds were seeded in nursery, and then transplanted in main land. At the end of first year of experiment, main panicle of some randomly selected plants were harvested and planted as a panicle-to-row at M2 generation. A semi-dwarf mutant line and an early maturity mutant line were obtained from 300 and 100 Gy respectively, at M2 generation. These mutant lines were showed no segregation at next generations. The height of semi-dwarf mutant line was 60cm shorter than the control (165cm). The length reduction of internodes 2 through 5 caused the height reduction in semi-dwarf line. Reduction in length of internode closed to panicle was more significant than the other internodes. There was no significant difference in panicle length between semi-dwarf mutant lines and control. The number of tillers in semi-dwarf mutant line was significantly more than the control (No.12). The yields of semi-dwarf line were less than control, because of some sterility caused by gamma rays. We are recovering fertility by back crossing of this line with control. Also an early maturity mutant line with 15 days earlier than parent was obtained. The yield of this mutant line was not significantly different from the control. Some traits were studied in mutant lines at M7 generation, they are includes: plant height, number of culm, uppermost internode length, second internode length, flag leaf length and width, days to heading, days to maturity, panicle length, grain length and width, Spikelet fertility, number of grain in panicle, grain yield, 100-grain weight, amylose (%), gel consistency and gelatination temperature. In this paper I will discuss the details of these traits. (author)