Symptomless Infection, Persistence, and Production of Pycnidia in Host and Non-Host Plants by Phomopsis batatae, Phomopsis phaseoli, and Phomopsis sojae, and the Taxonomic Implications

Abstract

Phomopsis batatae, P. phaseoli, and P. sojae were able to infect, without production of obvious symptoms, seedlings of sweet potato and of 16 legumes inoculated in the greenhouse. These fungi produced pycnidia on inoculated seedlings incubated in laboratory moist chambers. Under conditions of natural infection in the field, P. sojae was recovered from stems of 14 of 21 legumes. This fungus was also isolated from seeds of cowpea and lima bean as well as from soybean, its usual host. The interpretation of these results questions the validity of regarding these anamorphs as three distinct species. Taken with the close similarity in morphology reported for these taxa in the literature and observed in my own isolates and in herbarium specimens, I conclude that these taxa are all one species, the valid name of which is Phomopsis phaseoli (Desm.) Sacc. For similar reasons, I consider the teleomorphs Diaporthe phaseolorum var. batatatis, var. phaseolorum, and var. sojae to be one and the same taxon, D. phaseolorum (Cooke & Ellis) Sacc. I believe that teleomorphic and anamorphic isolates from stem cankers and blighted tops of soybean should be provisionally called D. phaseolorum f. sp. caulivora and P. phaseoli f. sp. caulivora, respectively, until it can be demonstrated by a non-wounding technique that they can cause these pathological conditions when re-introduced into the host.