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Tomato Early Blight Resistance in a Breeding Line Derived from Lycopersicon hirsutum PI 126445. A. F. Nash, Former Graduate Research Assistant, Department of Horticultural Science, North Carolina State University, Raleigh 27695-7609. R. G. Gardner, Associate Professor, Department of Horticultural Science, North Carolina State University, Raleigh 27695-7609. Plant Dis. 72:206-209. Accepted for publication 28 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0206.

Field studies were conducted in 1983, 1984, and 1985 comparing NC EBR-1, an early blight-resistant breeding line derived from Lycopersicon hirsutum PI 126445, with the resistant lines 71B2 and C1943 and with a susceptible check, Flora-Dade. Additional field studies were conducted in 1984 and 1985 comparing NC EBR-1 with the early blight-susceptible lines Piedmont and NC 8233(X)-2(X) and with the F1 hybrids of Piedmont and NC 8233(X)-2(X) crossed to NC EBR-1. Area under the disease progress curve (AUDPC) was used to measure resistance levels. AUDPC values for C1943, 71B2, and NC EBR-1 did not differ in any of the three seasons and were much lower in all three seasons than values for Flora-Dade. AUDPC values for NC EBR-1 were lower than for Piedmont and NC 8233(X)-2(X) in both years, and the F1s were intermediate to their respective parents in both years. In three greenhouse studies, lesion diameters resulting from point inoculation of leaflets were measured over time. NC EBR-1 had significantly smaller lesion diameters than NC 8233(X)-2(X) in all experiments. NC EBR-1 had significantly smaller lesion diameters than Piedmont in one experiment, and in two other experiments, there was a trend for smaller lesion diameters for NC EBR-1 than for Piedmont. The F1s were intermediate to their respective parents, but they were not always significantly different from either or both parents.

Keyword(s): Alternaria solani, tomato diseases.