Effect of Fusarium oxysporum f. sp. vasinfectum Inoculum Density, Meloidogyne incognita and Cotton Cultivar on Fusarium Wilt Development

Abstract

A greenhouse experiment was conducted to evaluate the interactive effects of different Fusarium oxysporum f. sp. vasinfectum isolates at increasing inoculum densities with Meloidogyne incognita on partially resistant (Stoneville (ST) 4554B2RF) and susceptible (FiberMAX (FM) 9058F) cotton cultivars. Disease incidence and area under the disease progress curve (AUDPC) were significantly higher for FM 9058F compared to ST 4554B2F for all the Fov isolates, densities and M. incognita combinations. Differences in pathogenicity were observed among the Fov isolates tested, suggesting that variability in aggressiveness may exist in populations of the fungus, though all isolates were within the same Race grouping (Race 1). A total of four isolates showed significantly higher AUDPC in the absence of M. incognita at higher inoculum densities of Fov; while two isolates had significantly higher AUDPC in the presence of M. incognita at low inoculum densities. Plant growth differed between cultivars where FM 9058F plants were shorter, and had decreased root, shoot, and total plant weights compared to ST 4554B2RF. Plants inoculated with M. incognita had root galls and were stunted with reduced shoot weight and total plant weight. Management of Fusarium wilt can be substantially improved by using partially resistant cultivars or reducing the inoculum density of root-knot nematode.