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.