Genotype x environment interactions. IV. The effect of the background genotype.

Experimental evidence from sternopleural chaeta number and yield of offspring in Drosophila melanogaster bears out the expectation (Mather, 1975) that the value of the regression of g, measuring genotype X environment interaction, on e, measuring the overall effect of environmental change , depends on genes in which the contrasting genotypes are alike as well as on the genes in which they differ. With yield of offspring there is evidence of some genotypes reacting to the environmental changes in the opposite direction to others.