Inheritance of resistance to blackmold (Alternaria alternata (Fr.) Keissler) in two interspecific crosses of tomato (Lycopersicon esculentum X L. cheesmanii f. typicum)
1994
Cassol, T. | St Clair, D.A.
Inheritance of resistance to blackmold, a disease of ripe tomato fruit caused by Alternaria alternata, was studied in two interspecific crosses. The parents, F1 and F2 generations of a cross between the susceptible Lycopersicon esculentum Mill. cultivar 'Hunt 100' and the resistant L. cheesmanii f. typicum Riley accession LA 422, and the parents, F1, F2, F3, and BC1 P2 generations of a cross between the susceptible L. esculentum cv. 'VF 145B-7879' and LA 422 were evaluated. The following disease evaluation traits were used: symptom rating (a symptom severity rating based on visual evaluation of lesions), diseased fruit (the number of diseased fruits divided by the total number of fruit scored), and lesion size (a function derived from the actual lesion diameter). Generation means analysis was used to determine gene action. The data of the 'Hunt 100' X LA 422 cross fit an additive-dominance model for all three traits. The 'VF 145B-7879' X LA 422 cross data best fit a model that included the additive x additive and additive X dominance interaction components for the trait diseased fruit, whereas higher-order epistatic models would have to be invoked to fit the data for the traits symptom rating and lesion size. A minimum of one gene segregated for all three traits. Broad-sense heritability estimates ranged from 0.09 to 0.16 for all three traits, indicating that selection for improved resistance to blackmold will require selection on a family performance basis.
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