Transmission potential of colletotrichum lindemuthianum (Race 65) in association with bean seeds under controlled conditions

Abstract

Anthracnose, caused by Colletotrichum lindemuthianum, is one of the main diseases affecting common bean in Brazil, and field losses can reach 100%. Transmission of this pathogen from seeds to seedlings/plants may vary according to environmental conditions and initial inoculum levels, among other factors. The aim of this study was to quantify the transmission rate of C. lindemuthianum, race 65, from infected bean seeds to seedlings/plants under controlled conditions. Seed inoculation was performed by the water conditioning technique in order to obtain seeds with different inoculum potentials as a result of the exposure time of the seeds to the fungus in pure culture, with the potentials denominated P0, P36, P72, P108, and P144. Inoculated and non-inoculated seeds were individually sown and kept in growth chambers under two temperatures, 20 and 26 °C, for a period of 28 days. There was transmission of the pathogen in both asymptomatic and symptomatic plants. The highest total transmission rate (92%) occurred in plants originating from seeds exposed for 144 hours to the fungus at 20 °C.