Soybean ( Glycine max): A new test system for study of genetic parameters as affected by environmental mutagens

Abstract

The light green, Y 11 y 11, plants of varieties T219 and L65-1237 of soybean have some dark green, yellow and twin (or double) spots resembling the phenotypes controlled by Y 11 Y 11, y 11 y 11 and Y 11 Y 11– y 11 y 11 genotypes, respectively. The process of somatic crossing over is considered responsible for the origin of double spots. Some of the single spots, undoubtedly, originate by failure of one of the two components of the double spots. Non-disjunction, segmental losses and/or point mutations are also inferred to cause some of the spots seen on the heterozygous Y 11 y 11 plants as well as light green spots seen on the Y 11 Y 11 and y 11 y 11 homozygotes. When seeds are treated with caffeine, mitomycin C or 3H 2O the increase in the frequency of all three types of spots on the Y 11 y 11 leaves is parellel. Somatic crossing over is considered as the major, common basis for the origin of spots. The treatment with sodium azide (NaN 3) increases, on the Y 11 Y 11 plants, the frequency of dark green and yellow spots equally; doubles increase only slightly or not at all. The y 11 y 11 plants lack any spots. The data suggest that NaN 3 causes non-disjunction in this material. γ-Rays, on the other hand, increase the frequency of yellow spots much more than that of dark greens or doubles on Y 11 y 11 leaves. Also light green spots are found on y 11 y 11 as well as Y 11 Y 11 plants. These data may mean that spots result from somatic crossing over, point mutations and segmental losses. A list of many other agents tested is included. Because different mutagens increase the frequency of the three types of spots, either equally or differentially, it is suggested that the pattern of action of a given mutagen can be studied by analyzing the relative increase of different types of spots. This material provides the investigator with a eukaryotic, in vivo test system which is relatively rapid and inexpensive.