Fusarium solani on Soybean Roots: Nomenclature of the Causal Agent of Sudden Death Syndrome and Identity and Relevance of F. solani form B

Abstract

Two morphological forms of Fusarium solani pathogenic on soybean, forms A and B, were further characterized and distinguished from other fungi. Questions regarding their identity were addressed. Soybean plants grown in the field and in a growth chamber were inoculated with Fusarium solani form A and F. solani f. sp. phaseoli. F. solani form A incited leaf symptoms typical of sudden death syndrome; F. solani f. sp. phaseoli did not. It was concluded that the two fungi are different and distinguishable on the basis of host specialization and the types of symptoms they incite on soybean. F. solani form A, the causal agent of sudden death syndrome, was designated F. solani (Mart.) Sacc. f. sp. glycines form. nov. Cultural and morphological characteristics of F. solani form B, the cause of seedling disease and root rot of soybean, and Plectosphaerella cucumerina were compared to determine the validity of a report indicating that they were conspecific. Results demonstrated that F. solani form B and P. cucumerina are distinctly different and not conspecific. The relevance of identifying and recognizing the two F. solani forms as separate and distinct members of the F. solani pathogen complex on soybean is discussed.