Pathogens causing anthracnose and fruit rots of coffee associated with the coffee berry borer and the Entomopathogenic Fungus Beauveria bassiana in Puerto Rico

Authors: Serrato Diaz, Luz; MARIÑO CÁRDENAS, YOBANA - University Of Puerto Rico; BAYMAN GUPTA, PAUL - University Of Puerto Rico

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2020
Publication Date: 7/22/2020
Citation: Serrato Diaz, L.M., Mariño Cárdenas, Y.A., Bayman Gupta, P. 2020. Pathogens causing anthracnose and fruit rots of coffee associated with the coffee berry borer and the Entomopathogenic Fungus Beauveria bassiana in Puerto Rico. Phytopathology. 110: 9. https://doi.org/10.1094/PHYTO-02-20-0057-R.
DOI: https://doi.org/10.1094/PHYTO-02-20-0057-R

Interpretive Summary: Fruit rot causes losses in coffee production worldwide. Eight species of the fungus Colletotrichum, C. acutatum, C. boninense, C. capsici, C. coffeanum, C. fructicola, C. gloeosporioides, C. kahawae and C. siamense, have been reported to cause rots and anthracnoses of coffee fruits. Of these, by far the most important is coffee berry disease (CBD), caused by C. kahawae and limited to Africa at high elevations. It is not known how these pathogens interact with the coffee berry borer (CBB, Hypothenemus hampei, the most devastating pest of coffee) and with Beauveria bassiana (Bb, a natural enemy of the CBB). We identified pathogens causing coffee fruits rots in Puerto Rico and evaluated whether Bb reduced fruit rot and CBB could disperse pathogens. A total of 2,333 coffee fruits perforated by CBB with and without Bb were collected in Puerto Rico; of these, 1,197 had Bb growth. Colletotrichum fructicola, C. siamense, C. theobromicola and C. tropicale were isolated and identified using morphology and phylogeny based on partial sequences of three nuclear genes. All four species caused internal and external rot after inoculation on green coffee fruit at 15 days after inoculation (DAI). Coffee fruits with Bb had significantly lower percent fruit rot than coffee fruits without Bb, suggesting Bb as a potential biological control against fruit rot. To test whether Bb had a protective effect against fruit rot, Bb and Colletotrichum were co-inoculated on coffee fruit in lab and field experiments, and percent fruit rot was evaluated 15 DAI. In both lab and field experiments, coffee fruits inoculated with both Bb and Colletotrichum had significantly less fruit rot than fruits inoculated with Colletotrichum alone. To test if CBB can be a dispersal agent of coffee fruit rot, CBBs were exposed to Colletotrichum conidia and placed on green coffee fruits; percent fruit rot was evaluated 15 DAI. CBBs impregnated with Colletotrichum spp. caused fruit rot, indicating that CBB can be a dispersal agent. 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 Bb in disease management and demonstrates CBB can disperse the pathogens.

Technical Abstract: Fruit rots reduce coffee production worldwide. Eight Colletotrichum species have been reported to cause coffee fruit rots; the most important is C. kahawae, 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 (Bb, a natural enemy of CBB) might reduce coffee fruit rots. We identified pathogens causing coffee fruits rots in Puerto Rico and evaluated whether Bb reduced fruit rot and whether CBB could disperse pathogens. 2,333 coffee fruit with CBB damage were collected; of these, 1,197 had Bb growth. Colletotrichum fructicola, C. siamense, C. theobromicola and C. tropicale were isolated and identified using morphological traits and phylogeny of three nuclear genes. All four species caused internal and external rot after inoculation on green coffee fruit. Coffee fruit treated with Bb had significantly less fruit rot than untreated fruit, suggesting Bb can protect against fruit rot. To test whether Bb had a protective effect, Bb and Colletotrichum were co-inoculated on coffee fruit. Fruit inoculated with both Bb 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 Bb in disease management and demonstrates CBB can disperse the pathogens.