Pathogens Causing Anthracnose and Fruit Rots of Coffee Associated with the Coffee Berry Borer and the Entomopathogenic Fungus Beauveria bassiana in Puerto Rico

Abstract

Fruit rots reduce coffee production worldwide. Eight Colletotrichum species have been reported to cause coffee fruit rots; the most important is C. kahawae, the cause of coffee berry disease (CBD) in Africa. It is unknown whether these fruit rot pathogens can be dispersed by the coffee berry borer (CBB, Hypothenemus hampei) or whether Beauveria bassiana (a natural enemy of CBB) might reduce coffee fruit rots. We identified pathogens causing coffee fruits rots in Puerto Rico and evaluated whether B. bassiana reduced fruit rot and whether CBB could disperse pathogens. A total of 2,333 coffee fruit with CBB damage were collected; of these, 1,197 had visible growth of B. bassiana. C. fructicola, C. siamense, C. theobromicola, and C. tropicale were isolated and identified from the fruit using morphological traits and phylogeny of three nuclear genes. All four species caused internal and external rot after inoculation of healthy green coffee fruit. Coffee fruit treated with B. bassiana had significantly less fruit rot than untreated fruit, suggesting B. bassiana can protect against fruit rot. To test whether B. bassiana had a protective effect, B. bassiana and Colletotrichum were coinoculated on coffee fruit. Fruit inoculated with both B. bassiana and Colletotrichum had significantly less rot than fruit inoculated with Colletotrichum alone. To test if CBBs dispersed the pathogens, CBBs were exposed to Colletotrichum conidia and placed on green fruit, which resulted in fruit rot. This study identifies new pathogens causing coffee fruit rot, shows that C. kahawae is not the only Colletotrichum that attacks green fruits, suggests a role for B. bassiana in disease management and demonstrates CBB can disperse the pathogens.