Alpha-amanitin resistance in three wild strains of Drosophila melanogaster.

Three wild strains of D. melanogaster have been identified which are resistant to normally lethal levels of the fungal toxin, alpha-amanitin. Dietary LD50S for Oregon-R, the reference strain, and Ama-KTT, Ama-MI and Ama-KLM, the resistant strains, are 1.2, 35, 30 and 10 micrograms alpha-amanitin/vial, respectively. Resistance in all three strains is a digenic trait, being determined by two independently acting dominant genes, Ama-1, Ama-2, either of which is sufficient to confer resistance and which are located at approximately 18.8 and 100.7, respectively, on chromosome 3. Resistance to alpha-amanitin in all three strains is apparently not mediated by modification of RNA polymerase form II nor by failure of toxin transport or by toxin inactivation.