Extending number of days to first bloom is a positive means for increasing total growth for short-season, determinate growth habit soybeans . Increasing number of days to first bloom is also effective in increasing the height of lowest pods. In an attempt to develop productive strains of Group IV maturity with good quality seed, we used PI 171.450 as a parent.

The male-sterile (female-fertile) mutant ms1 is identified by three characteristic features. Kenworthy et al. (1973) reported occurrence of twin seedlings, at a low frequency. We are reporting the two additional characteristics: failure of cytokinesis following telophase II; and production of twice as many pollen mother cells as are found in male-fertile sibs.

Some mutants and mutation-derived lines of 'S.J.2' and 'Sansai' soybean varieties were obtained after seed irradiation with gamma rays (Smutkupt, 1973; Smutkupt and Gypmantasiri, 1974). Among .them, three of S.J.2 lines, three of Sansai lines, including each control and one 'S.J.l' line (see Table 1) were selected to evaluate for seed yield, protein, oil, fatty acid composition, and other characteristics. Certain plant characteristics of these selected lines are shown in Table 1.

Chief', a very tall Maturity Group IV variety, was used as a donor parent in backcrossing to 'Clark' to transfer Np (a gene for high phosphorus tolerance). In the field in 1963, I grew progenies from 40 selected Np F2 plants from Clark BC5 and was surprised to see 2 of the progenies uniformly very tall and 3 of them segregating approximately 1/4 tall plants. The Np gene appears to have no effect on field-grown plants in normal soils.