VIEW ARTICLE

Ecology and Epidemiology

Influence of Glomus fasciculatus and Soil Phosphorus on Verticillium Wilt of Cotton. R. M. Davis, Graduate research assistant, Department of Plant Pathology, University of California, Riverside, CA 92521; J. A. Menge(2), and D. C. Erwin(3). (2)(3)Assistant professor, and professor, respectively, Department of Plant Pathology, University of California, Riverside, CA 92521. Phytopathology 69:453-456. Accepted for publication 3 November 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-453.

A sandy soil received superphosphate at 20 or 300 μg of P per gram of soil, and at each P regime soil was infested with Verticillium dahliae alone, Glomus fasciculatus alone, both fungi, or neither fungus. In plants fertilized with 20 μg of P per gram of soil, Verticillium wilt was more severe in cotton plants infected with the vesicular-arbuscular mycorrhizal fungus, G. fasciculatus, than in nonmycorrhizal plants. However, in plants fertilized with 300 μg of P per gram of soil, Verticillium wilt was equally severe in mycorrhizal and nonmycorrhizal plants. In plants fertilized with 20 μg of P per gram of soil, there were more propagules of V. dahliae in petioles of mycorrhizal plants than in petioles of nonmycorrhizal plants. In plants fertilized with 300 μg P per gram of soil, numbers of propagules of V. dahliae were not significantly different in mycorrhizal and nonmycorrhizal plants. Infection of cotton by G. fasciculatus was not affected by V. dahliae in plants fertilized with 20 μg of P per gram of soil, but infection was inhibited by P and further inhibited by V. dahliae in plants fertilized with 300 μg of P per gram of soil. Concentrations of P in leaves of mycorrhizal and nonmycorrhizal plants fertilized with 20 μg of P per gram of soil were similar, but concentrations of P were lower in plants infected with V. dahliae alone than in plants infected with both V. dahliae and G. fasciculatus.