Induction of Useful Short Stature and Early Maturing Mutants in two Japonica Rice Cultivars1

Abstract

Short stature and early maturing mutants were induced in two japonica rice (Oryza sativa L.) cultivars by 60Co gamma irradiation. Frequency of useful mutants in the M2 generation grown from bulked seed of M1 plants was 1.89% in ‘Calrose’ and only 0.62% in ‘Colusa.’ The most promising mutant was the short stature Calrose selection D7.D7 was about 25 cm shorter than its parent cultivar Calrose. In 11 large‐plot tests conducted over 2 years, D7 equaled the yield of the tall check cultivar ‘CS‐M3’ (a cultivar similar to Calrose), was 35 cm shorter and had more lodging resistance. The short stature of D7 was controlled by a single recessive gene.Two early maturing Calrose mutants, D18 and D31, may be useful as germplasm sources of early maturity. One short stature, early Colusa mutant, D38, may also be useful as germplasm.Several different short stature phenotypes were induced in Calrose. When Calrose M1 plants from the 25 kR treatment were handled in a pedigree fashion, nearly 10% of the M1 plants produced mutants possessing some degree of short stature.