Reproductive consequences of Colletotrichum lindemuthianum (Ascomycota) infection on wild bean plants (Phaseolus vulgaris)

Abstract

Fungal plant parasites can have strong reproductive consequences on their hosts, but little is known about the amount of parasite-induced fitness loss under natural conditions. We present data from wild populations of Colletotrichum lindemuthianum Sacc. & Magn., a fungal parasite that attacks the wild common bean (Phaseolus vulgaris L.). We estimated disease prevalence in two populations and fungal virulence by examining naturally infected plants for three fitness-related traits: number of seeds per pod, mass of seed per pod, and germination rate. We observed that C. lindemuthianum infected nearly all plants in the study populations, but that the amount of infected pods per plant varied greatly. In addition, infection was associated with a reduction of host fitness-related traits only in pods with sporulating lesions. These findings suggest that C. lindemuthianum may constitute a significant selection pressure in wild populations, and that impact of spore production on host fitness may influence virulence evolution in this fungus.