Submitted to: Sociedad Espanola de Fitopatologia
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1996
Publication Date: N/A
Technical Abstract: Significant losses in melon ( Cucumis melo L.) production, due to vine collapse, have occurred along the Mediterranean coast of Spain since the early 1980's. Isolations from 1987 through 1994 showed that Acremonium cucurbitacearum was the predominant pathogen. It was isolated from 94% of the 165 melon fields sampled. Monosporascus cannonballus was isolated from 26%, both fungi were present in 20%, and 6% of the fields had M. cannonballus alone. Greenhouse studies were conducted to evaluate seedling disease reaction in response to different CFU/g of soil and to compare virulence of Spain isolates with isolates from the United States. The cultivar Magnum 45' of C. melo was used in these tests. Relative virulence tests using three isolates of each fungus were conducted 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 for A. cucurbitacearum. Based on comparisons with M. cannonballus isolates from California and Texas (United States), isolates from Spain are generally less virulent. A large percentage of Spanish isolates appear to be afflicted with the dsRNA. Additional isolates, using 20 CFU/g of soil, need to be tested to more accurately determine virulence within the population of M. cannonballus in Spain. Based on root damage ratings, Spain isolates of A. cucurbitacearum were highly virulent. California isolates were similar in virulence to the Spain isolates and the Texas isolates were generally less virulent than either. Based on the conditions of these studies, the required CFU/g of soil for evaluating pathogenicity and relative virulence of A. cucurbitacearum on C. melo was determined to be 10,000.