Physiological Races of Colletotrichum lindemuthianum, the cause of Bean Anthracnose in Major Bean Growing Regions of Southern and Central Ethiopia

Background: Bean anthracnose (Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara) is one of the major diseases of common bean (Phaseolus vulgaris L.) in Ethiopia causing up to a 63% yield loss. However, information regarding the race variability of the pathogen in Ethiopia is limited.Objectives: The current study was initiated with the objective of characterizing races of C. lindemuthianum prevailing in major bean producing areas in southern and Central Ethiopia.Materials and Methods: Thirty isolates of C. lindemuthianum, collected from potential bean growing districts of Damot Gale, Halaba Special, Melkassa, Hawassa Zuria, and Boricha in 2017 were inoculated on to 12 differential cultivars in a greenhouse using a completely randomized design.Results: The results revealed the presence of 17 physiological races (pathotypes) of the pathogen, of which only three were previously reported from Ethiopia. Race 9 was found to be the most dominant one across the surveyed areas. Four races (2073 from Halaba Special, 2225 from Damot Gale, 2260 from Melkassa, and Hawassa Zuria, and 3047 from Boricha districts) were able to infect the highly resistant differential cultivar G2333, indicating that the Ethiopian C. lindemuthianum populations might be composed of highly virulent races. The cultivars Michelite, Mexico 222, and PI 207262 showed the most susceptible reaction to the tested races, while no cultivar was immune to the pathogen races. The results have demonstrated the existence of highly variable isolates of C. lindemuthianum that cause bean anthracnose in Ethiopia.Conclusions: The Ethiopian bean anthracnose pathogen (Colletotrichum lindemuthianum) has high variability. The pathogen seems to be widely distributed in all studied bean growing areas with highly virulent as well as less virulent races. It is also suggested that the C. lindemuthianum population in Ethiopia could possibly be composed of highly virulent races that can cause much damage even to resistant/tolerant germplasm. The results provides important useful insights into future breeding programs for developing host resistance against bean anthracnose in the country. Identifying the race should continue using techniques that are more advanced and by including additional isolates across different agro-ecological settings in the country.