VIEW ARTICLE

Ecology and Epidemiology

Reduction of the Effects of Pathogenic, Root-Infecting Fungi on Soybean by the Mycorrhizal Fungus, Glomus mosseae. L. Zambolim, Former graduate student, Department of Plant Pathology, University of Florida, Gainesville 32611, Current address of senior author: Departmento de Fitopatologia, Universidade de Viçosa, Viçosa, Minas Gerais 36570, Brazil; N. C. Schenck, professor, Department of Plant Pathology, University of Florida, Gainesville 32611. Phytopathology 73:1402-1405. Accepted for publication 20 April 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1402.

Soybean growth responses to Glomus mosseae in combination with either Macrophomina phaseolina, Rhizoctonia solani, or Fusarium solani were studied using autoclaved and/or nonautoclaved field soil (91 ppm P and pH 6.8) in a greenhouse with air temperatures varying from 25- 35 C. After 45 days, plants in autoclaved soil containing either M. phaseolina, R. solani, or F. solani had significantly less root weight, shoot weight, or plant height than control plants in soil not infested with either G. mosseae or the pathogens. Plants exposed to either M. phaseolina, R. solani, or F. solani in autoclaved and nonautoclaved soil had 20- 30% and 10- 16% less seed weight, respectively, than control plants. G. mosseae did not affect the incidence of infection of soybean by the pathogens but the pathogens significantly reduced (average 38%) root colonization by G. mosseae in autoclaved soil. The addition of G. mosseae to autoclaved soils with and without the pathogens significantly increased plant growth responses. Plants with G. mosseae had seed yields increased 50 and 15% in autoclaved and nonautoclaved soil, respectively, over that of comparable control plants without G. mosseae. Significant correlations occurred between the percentage of roots colonized by G. mosseae and root weight, shoot weight, and plant height. The correlation between seed weight and plant growth responses at 45 days was also significant. Although the incidence of infection by the pathogens was about the same in mycorrhizal and nonmycorrhizal plants, plants colonized by G. mosseae appeared to tolerate this infection by the pathogens better than did nonmycorrhizal plants.