|GORDON, T R|
|DAVIS, R M|
Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: 8/11/1995
Publication Date: N/A
Technical Abstract: Monosporascus cannonballus and an Acremonium sp. have been associated with vine decline and/or vine collapse of watermelon and cantaloupe in California. Pathogenicity and virulence evaluations of numerous isolates often have given erratic results. Greenhouse studies were conducted to evaluate seedling disease reaction in response to different CFU concentrations. Three isolates of each fungus were tested using 0, 5, 10, 20, 30, 40, and 50 CFU/g of soil for M. cannonballus and 0, 1,000, 10,000, 20,000, 30,000, 40,000, and 50,000 CFU/g of soil for Acremonium sp. Cucumis melo cv Magnum 45 were evaluated 28 days after planting. Based on root rot ratings, plant stunting, and differential isolate virulence, the optimum CFU/g of soil for evaluating pathogenicity was determined to be 20 for M. cannonballus and 10,000 for Acremonium sp. Some of the less virulent isolates may appear non-pathogenic at these densities but the moderate to highly virulent isolates can be evaluated without overwhelming the plants. Because different isolates of each fungus produce drastically different inoculum densities, it is paramount that CFU's be determined when comparing pathogenicity and virulence between isolates.