First report of Didymella fabae, teleomorph of Ascochyta fabae, on faba bean crop debris in Tunisia

Abstract

Ascochyta blight of faba bean, caused by Ascochyta fabae, is one of the most destructive diseases of faba bean (Vicia faba) in Tunisia. Yield losses caused by the disease can reach 35% under conditions favourable for disease development. Despite its widespread occurrence, only the asexual part of Ascochyta life-cycle has been recovered in Tunisia. However, the sexual stage of the fungus is suspected to play an important role in the epidemiology of the disease, given the distribution of the primary infection symptoms. Pseudothecia of Didymella fabae, the teleomorph of A. fabae, were first observed in autumn-winter 2010‒2011, on faba bean debris collected from the region of Beja (Tunisia) and placed in three different locations. Mature pseudothecia were first observed 2 months after the debris placement, with the typical characteristics of Didymella fabae. Isolation from ascospores resulted in typical cultures of A. fabae which produced typical symptoms of the disease when used to inoculate faba bean seedlings. This is the first report of D. fabae in Tunisia. The occurrence of the teleomorph has important implications for epidemiology of Ascochyta blight and therefore, on its management in faba bean crops.