Inheritance of Tomato Late Blight Resistance from 'Richter's Wild Tomato' and Evaluation of Late Blight Resistance Gene Combinations in Adapted Fresh Market Tomato Backgrounds

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Late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary, is a destructive disease of tomato worldwide. Originating in the highlands of central Mexico, through migration, mutation, and sexual recombination, this pathogen has proven mobile and highly variable. Three monogenic R genes (Ph-1, Ph-2, and Ph-3) for resistance to late blight have been identified in tomato. However, P. infestans isolates which overcome each of these individual R genes have been documented. The objectives of this research were to characterize the inheritance of late blight resistance in the home garden tomato 'Richter's Wild Tomato', to determine if this resistance is allelic to any of the three previously identified resistance sources, and to evaluate late blight resistance of R gene F1 hybrid combinations relative to individual R genes. 'Richter's Wild Tomato' was crossed with NC215E-1, a late blight susceptible fresh market breeding line, and evaluation of derived BC1F2, BC2F2, and BC3F1 populations indicated single gene inheritance of late blight resistance. Evaluation of an F2 population derived from the cross 'Richter's Wild Tomato' x 'Legend' (Ph-2) indicated that the monogenic resistance conferred by 'Richter's Wild Tomato' was allelic to Ph-2. Combinations of Ph-2, either from 'Richter's Wild Tomato' or 'Legend', and a fresh market line possessing Ph-3 displayed superior resistance versus individual R genes and other R gene combinations in North Carolina field trials under natural inoculation. Combined resistance has the potential to not only provide a superior level of resistance, but to also be more stable over time.



phytophthora infestans, late blight





Horticultural Science