SUSCEPTIBILITY OF INBRED LINES OF OILSEED RAPE, BRASSICA-NAPUS, TO FEEDING DAMAGE BY THE CRUCIFER FLEA BEETLE, PHYLLOTRETA-CRUCIFERAE (GOEZE) [COLEOPTERA, CHRYSOMELIDAE], AND ITS INHERITANCE

Seventy-seven inbred lines of Brassica napus L. were assessed for antixenosis to damage by the crucifer flea beetle, Phyllotreta cruciferae (Goeze). The resistance was quantified by measuring the level of damage inflicted on seedlings of each line in laboratory tests. One of these lines, M12, was more susceptible than another line, L19, in a series of replicated tests, but individual seedlings could not be identified as resistant or susceptible because inter-seedling variation in the damage level was high. The F3 families from reciprocal crosses between L19 and M12 showed segregation for the resistance, demonstrating that the antixenosis has a genetic basis. Two or more genes probably control the expression of the resistance, but the number could not be estimated. Electrophoresis of seed endosperm proteins revealed a band, P-74, that occurred in M12 and eight cultivars of B. napus, but not in L 19. This banding pattern was inherited as a simple recessive allele, but it proved not to be linked with the resistance in the F3 families. Further screening of B napus for highly resistant genotypes and identification of linked genetic markers are needed to establish agronomically useful levels of flea beetle resistance in this crop.