Diallel analysis of resistance in carrot to Alternaria leaf blight

Diverse carrot (Daucus carota L.) inbreds were evaluated as young plants in the greenhouse and mature plants in the field for resistance to the pathogen Alternaria dauci (Kuhn) Groves and Skolko. Persistence of leaves after infection was the criterion used to estimate disease damage by the pathogen. Partial resistance was identified. A five-parent diallel evaluated for resistance indicated a preponderance of additive variation with some dominant gene action for resistance. Reciprocal cross differences were significant for certain crosses, Responses of most inbreds were useful in predicting resistance in their hybrids, but exceptions to this trend did occur. Field resistance ratings generally correlated well with resistance ratings obtained in greenhouses, even in grower fields where fungicides were applied.