Induction of earliness and awnless mutants in rice (Oryza sativa L.) Domsiah cultivar

Domsiah is one of local rice cultivar with best quality in Iran, but it is nearly late with long awn. This study was conducted to induce earliness and awnless characterstics in Domsiah cultivar from 1995 to 1999. The seeds were irradiated with gamma rays at 100, 200 and 300 Gray, and Dimethyl Sulfate (DMS) at 0.1%, 0.2% and 0.3%(for 24 hrs. in room temperature), separately. At the end of first year of study, main panicels of some randomly selected plant were harvested and planted at M2 generation as a panicle-to-row. Results showed no sigificant varition among the DMS treatments, hence these treatments were removed from the study. Four early mutant populations (E1 to E4) were obtained from treatments of gamma rays at M2 generation. These mutant populations showed segregation for maturity. Meanwhile, the E1 population showed segragation for awnless. The plant height, culm number, maturity and panicle length were studied in mutant lines at M3 generation. The E3 line was 15 days earlier than control at M4 generation. The plant height of this line was significantly different compared to control, the awnless mutant line was also shorter and earlier. In order to study some morphological characteristics and yield at M5 generation, the E3 and awnless mutant lines were planted in randomized completed block design with three replications in Rasht and Tonekabon in 1999 and 2000. The characteristics under study were included: plant height, culm number, peduncle, second internode length, flag leaf length and width, days to panicle emergence (DPE), days to maturity (DMA), panicle length, grain length and width, spikelet fertility, grain no. per panicle, grain yield, 100-grain weight, amylose (%), gel consistency and gelatination temperature. There were no significant differences in second internode length, DPE, spikelet fertility, amylose %, gel consistency and gelatination temperature. Generally, the correlation coefficient between DPE and DMA in rice is positive and significant, however, it was found non significant in this study. Because of highly significant correlation (r =0.7**) between yield and 100-grain weight, it is possible to improve grain yield through 100-grain weight. Although, there was not a significant difference between early mutant and awnless lines in DMA, however, 100 grain weight and no. of grain per panicle in awnless mutant line were higher than in early mutant line. These two mutant lines has significant difference for DMA compared to control i.e. they were 13 days earlier than control