Seeds of S.J.2, a Thai soybean variety, were treated with gamma rays of a cobalt source in five different doses: 5, 10, 15, 20 and 30 krad, respectively. In M2 generation , yellow seedlings appeared in the treated materials, with the frequency ranging from 0.20 to 0.70%. Two different types of yellow seedlings were observed.

Glycine max (L.) Merrill (soybean) is said to have at least 18 loci responsible for the development of chlorophyl (Bernard and Cremeens, 1970). One of these, y11, discovered by Weber and Weiss (1959), is characterized by the development of golden yellow color of the leaves and stem in homozygous (y11 y11 ) combination. The heterozygous plants are light green and differ from the y11y11 homozygotes which have normal, dark green color.