Tan spot of lima bean caused by Boeremia exigua var. exigua in New York State, USA

Abstract

In 2013, a new foliar disease was observed in processing lima bean (Phaseolus lunatus L.) plants in fields across western New York State, USA. The fungus Boeremia exigua var. exigua (Desm.) Aveskamp, Gruyter & Verkley was consistently isolated from lesions. The fungus was identified by characterization of morphological features and multiple genes (internal transcribed spacer, partial actin, β-tubulin, translation elongation factor 1-α and calmodulin) informative for speciation within the Didymellaceae. Pathogenicity was confirmed by inoculation of three lima bean cultivars in a repeated greenhouse experiment. Snap bean (Phaseolus vulgaris L.) and soybean (Glycine max (L.) Merr.), which are commonly encountered in the cropping rotation in New York State, were also inoculated, and demonstrated susceptibility to the pathogen. To the best of our knowledge, this is the first report of Boeremia exigua var. exigua causing tan spot disease on foliage of lima bean in New York State, USA.