An efficient method for inducing sporulation of cercosporoid fungal species causing leaf spots in cassava

Abstract

This study aimed to develop an efficient method for inducing sporulation of three species of cercosporoid fungi (Cercospora manihobae, Passalora henningsii, and Passalora vicosae) causing leaf spots in cassava. We evaluated a method using mycelial fragments shake-incubated in liquid culture medium followed by a drying process. All evaluated media (potato dextrose, vegetable broth, and V8 juice at concentrations of 10% and 20%) were efficient in inducing sporulation of the species, but in different amounts. The highest conidial production (from 1.8 × 104 to 5.6 × 104 conidia mL−1) was achieved when the isolates were cultured on V8 medium, regardless of the concentration (10 or 20%). In addition, we verified that the conidial production increased when the isolates were cultured in liquid medium under agitation for a longer time. The optimal time of incubation was different for the three species (on average 12.8 days for C. manihobae, 16.7 days for P. vicosae, and over 15 days for P. henningsii). The findings will be useful for studies requiring abundant production of cercosporoid conidia of cassava in artificial media.