Effects of Fusarium Inoculum Density and Root-Knot Nematodes on Wilt Resistance in Summer Squash. C. M. Caperton, Former Graduate Research Assistant, Texas A&M University System, College Station 77843. R. D. Martyn and J. L. Starr, Associate Professors, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, Texas A&M University System, College Station 77843. Plant Dis. 70:207-209. Accepted for publication 28 August 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-207.

Resistance of summer squash (Cucurbita pepo var. melopepo) cultivars to Fusarium oxysporum f. sp. niveum (F. o. niveum) was dependent on the concentration of initial inoculum and, in one cultivar, on the presence of root-knot nematode (Meloidogyne incognita). Four cultivars (Hyfric, Golden Eagle, Straightneck, and Early Prolific Straightneck) showed increasing susceptibility to Fusarium wilt as the concentration of F. o. niveum increased from 10³ to 10⁶ microconidia per milliliter. Cultivars Crookneck and Goldneck were unaffected by increasing levels of F. o. niveum. With the moderately wilt-resistant cultivar Early Prolific Straightneck, concomitant infection with M. incognita increased both the earliness of symptom development and the total wilt incidence. Resistance in the highly Fusarium wilt-resistant cultivar Goldneck was unaffected by the root-knot nematode. All squash cultivars tested were equally and highly susceptible to M. incognita on the basis of degree of root-galling and egg-mass production.