A 6-parent diallel was used to study combining ability and type of gene action contributing to resistance in tomato (Lycopersicon esculentum Mill.) to anthracnose caused by Colletotrichum dematium (Pers. ex Fr.). The 6 parents, one set of F1, hybrids, and 5 selected reciprocal crosses were grown at 2 locations. Ripe fruit were harvested, puncture-inoculated with the pathogen, and subsequently evaluated for resultant lesion diameter. No reciprocal effects were found at either location for the 5 crosses studied. The analysis of variance for parent and F1 hybrid performance revealed a genotype × location interaction. Combining ability analysis based on the F1 hybrids alone indicated a significant general combining ability (GCA) effect. The specific combining ability (SCA) and GCA × location interaction mean squares were smaller than the GCA value but were still significant. Differential performance over locations of the hybrids of one line was primarily responsible for the GCA × location interaction. Analysis of variance and covariance of parental arrays indicated partial dominance in the direction of susceptibility. Narrow sense heritability for the trait was 70% over both locations.
Research Plant Pathologist.
Received for publication June 6, 1983. Scientific Article No. A-3472, Contribution No. 6545 of the Maryland Agricultural Experiment Station (Dept. of Horticulture). The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.