INHERITANCE OF DIELDRIN-RESISTANCE IN THE ONION MAGGOT

Abstract
A dieldrin- resistant strain of Hylemya antiqua from Thedford, Ont. was crossed with a normal strain, and the manner of inheritance to the F2 indicated that the dieldrin-resistance was due to a single main gene allele, neither dominant nor recessive. Diagnostic dosages distinguishing the 3 genotypes were established for the following adult susceptibility test methods: topical application, spray tower, and impregnated paper. Application of these dosages to test data for field populations indicated that dieldrin- resistant onion maggot at La Salle, Ont. in 1961 contained approximately 90% homozygotes for the resistance gene.