APS Abstract of Presentation

Fraser fir, a new host of Phytophthora capsici
L. M. QUESADA OCAMPO (1), D. W. Fulbright (1), M. K. Hausbeck (1)
(1) Michigan State University, East Lansing, MI, USA
Phytopathology 98:S129

Phytophthora cinnamomi, P. drechsleri, P. citricola and P. cactorum limit Fraser fir production whereas P. capsici affects primarily vegetable crops. Our objectives were to determine whether P. capsici can infect and cause disease on Fraser fir. Seedlings were stem-inoculated (no wound or 1- or 3-mm-diameter wound) with P. capsici isolate OP97 and incubated in growth chambers at 20 or 25°C. Four diverse isolates were used to stem-inoculate seedlings (no wound or 1-mm-diameter wound) incubated at 25°C. Seedlings were soil-inoculated (2 or 4 g of infested millet seed and 2 or 5 × 10(^3) zoospores/ml of a zoospore solution) with OP97 and incubated at 25°C. Four isolates were used to soil-inoculate seedlings (2 or 4 g of infested millet seed) incubated at 25°C. Four hundred seedlings were planted in vegetable fields with a known history of P. capsici. Experiments were conducted twice and controls were included. All P. capsici isolates infected inoculated seedlings despite the inoculation method or incubation temperature used. Seedlings planted in the field presented symptoms and died (72%). The pathogen was reisolated from symptomatic seedlings and the phenotype (mating type and mefenoxam resistance) was confirmed for inoculated seedlings and determined for isolates from seedlings planted in the field. Identification was confirmed by species-specific PCR. To our knowledge, this is the first report of P. capsici infecting Fraser fir. This study suggests that planting Fraser fir in fields infested with P. capsici could result in infection.

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