We irradiated seeds of variety Seratus Malam with different doses of gamma rays (10, 20, 30, and 40 krad) in 1983. The M2 generation plants were selected for semidwarf stature, and from 50,000 M 2 plants, 130 semidwarf mutants were selected. A semidwarf mutant, SM-268 /PsJ, selected from the 20-krad treatment, was used for analysis of allelic relationship. In the allelic test, semidwarf mutant SM-268/PsJ was crossed with IR36. However, in the F3 an early maturity line Obs-1647/PsJ was selected and tested for yield potential in the F10 generation. The agronomic characters of Obs-1647/PsJ and the mother varieties are in Table 1.