Genetical variation for enzyme activity in a population of Drosophila melanogaster. VII. Genotype-environment interaction for alcohol dehydrogenase (ADH) activity.

Genotype-environment interaction was detected for ADH activity amongst a set of 18 highly inbred lines of Drosophila melanogaster which had been extracted from the laboratory population, "Texas". The genotype-environment interaction for ADH activity was not wholly associated with genotype-environment interaction for body weight or total protein level. Detailed analyses of the responses of the individual inbred lines in ADH activity in relation to the environmental index, ej and following the procedure of Jinks and Pooni (1979), showed substantial diversity in the form of response. Lines homozygous for the AdhF allele were more environmentally sensitive than AdhS/S lines. Amongst the 16 AdhS/S lines, models of linear, quadratic or two intersecting-straight-lines were used to illustrate the varied responses of genotypes to the environment. The heterogeneity in the response characteristics of the inbred lines was attributed to variations in the conditions of culture media normally present within populations and laboratories. Moreover the non-linear responses shown by some lines to the environment are consistent with a model of genotype-environment interaction for ADH activity mediated by varied genotype-specific sensitivities to different environmental factors.