Fusarium solani from Ascospores of Nectria haematococca Causes Sudden Death Syndrome of Soybean

Abstract

This is the first report of a teleomorph connection for isolates of Fusarium solani that infect soybean. Nectria haematococca isolated from roots of soybean plants with sudden death syndrome proved to be the ascoma stage of F. solani. A single ascospore culture IN-2X-11A from IN-2X-11 produced sporodochia with masses of blue macroconidia and essentially no microconidia. Another single asco? spore culture IN-2X-11B from IN-2X-11 did not produce macroconidia, but it did produce the perfect state and microconidia. Hypocotyl inoculation of soybeans with macroconidia plus mycelia of IN-2X11A caused severe foliar symptoms typical of sudden death syndrome. In contrast, no foliar symptoms of sudden death syndrome developed in plants inoculated with microconidia plus mycelia. Pathogenicity ofthe N. haematococca isolate producing abundant F. solani macroconidia has been stable in inoculation tests since 1989, and it is more virulent than several other Indiana isolates of F. solani from soybean plants with severe sudden death syndrome.