Major genes for copper tolerance in Mimulus guttatus

Abstract

HEAVY metal tolerance in higher plants has proved to be an excellent model system which has provided insight into several aspects of the evolutionary process (see ref. 1 for review). But comparatively little is known about the formal genetics of this character in higher plants, since the grasses which have been the subject of most of the ecological work are not readily amenable to genetic analysis. Antonovics et al.1 argue that the data indicate that tolerance is governed by a polygenic system, though it has been shown that in yeast2,3 and Paramecium4 that major genes are responsible. The discovery5 that the yellow monkey flower, Mimulus guttatus, has also developed copper tolerant races has enabled this hypothesis to be tested—the genetics of M. guttatus are readily investigated since it is easily destaminated and crossed, produces up to 400 seeds at a time, and can complete a generation in less than 100 d. The data presented here suggest that there are only two genes responsible for most of the tolerance observed in this plant.