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Evaluating Strawberry Plants for Resistance to Colletotrichum fragariae. Bryan R. Delp, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650. R. D. Milholland, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 64:1071-1073. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-1071.

A reliable technique for evaluating strawberry plants (Fragaria × ananassa) for resistance to Colletotrichum fragariae involves spraying the distal half of attached petioles with a 106 conidia per milliliter suspension, incubating at 100% RH and 2830 C for 48 hr and then maintaining the plants near 25 C. A disease index was developed based on petiole reactions; flecking was considered resistant and girdling to petiole death was susceptible. Because plants inoculated in the crown died, this method was discontinued. The age of inoculum did not affect the amount of infection. Optimum inoculum density for resistance evaluation was 106 conidia per milliliter. Optimum time in the moist chamber was 48 hr; all plants became susceptible after 72 hr. Optimum temperature was 25 C; resistant cultivars became susceptible at 30 C.