|ROJAS, E. - University Of Maryland
|VAN BAEL, S. - Smithsonian Tropical Research
|HERRE, E.A. - Smithsonian Tropical Research
|CANNON, P.F. - Commonwealth Agricultural Bureau International (CABI)
|CHEN, R. - China Education And Research Network
|PANG, J. - China Education And Research Network
|WANG, R. - China Education And Research Network
|ZHANG, Y. - China Education And Research Network
|SHA, T. - Yunnan University
Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2009
Publication Date: 10/14/2010
Citation: Rojas, E., Rehner, S.A., Samuels, G.J., Van Bael, S., Herre, E., Cannon, P., Chen, R., Pang, J., Wang, R., Zhang, Y., Sha, T. 2010. Colletotrichum gloeosporioides s.l. associated with Theobroma cacao and other plants in Panama: multilocus phylogenies distinguish host-associated pathogens from asymptomatic endophytes. Mycologia. 102(6):1318-1338.
Interpretive Summary: Fungi are a diverse group of organisms that cause serious diseases of agricultural crops but can also protect plants from diseases. One group of fungi causes diseases called anthracnose on many different kinds of plants. Similar fungi are being considered for use to protect plants from diseases. However, it is not known if the fungi that cause disease are really different from those that protect plants. In this research fungi that cause diseases primarily from the chocolate plant were compared with fungi that protect plants. It was determined that some species cause diseases of specific crops such as cacao and mango. Other similar-looking but slightly different species also from cacao exist within the plant but do not cause disease while others can be used to protect the plant. Molecular sequences were used to rapidly distinguish these species. Plant pathologists will use this research to control diseases using helpful fungi.
Technical Abstract: Species of Colletotrichum interact with a vast but as yet undetermined number of plant species as pathogens and as asymptomatic endophytes. It is not known, however, whether these contrasting ecological modes are optional strategies exercised by individual species or whether species ecology is more narrowly circumscribed as either pathogenic or endophytic. We used single and multilocus phylogenetics to assess diversity, establish species boundaries, and evaluate host range and ecological mode within a collection of 77 Neotropical Colletotrichum endophytes and pathogens isolated from cacao and other plants from Panama. Nucleotide variation at introns located in the 5' end of elongation factor-1 (5'-tef1) accurately diagnosed terminal clades and branches that were also resolved and supported in an independent multilocus phylogeny; 5'-tef1 may therefore be useful as a prospective diagnostic marker for screening Colletotrichum biodiversity and for species identification. C. gloeosporioides s.l., which predominated in the Panamanian collection, consists of at least seven phylogenetically distinct lineages, including two clades of host-associated pathogens specific to either cacao or mango and five clades of endophytes. Pathogen species were not isolated as endophytes nor were endophyte species isolated from visibly diseased leaves or unripe fruits. The ability of the cacao pathogen to cause leaf anthracnose symptoms was demonstrated in pathogenicity tests and Koch's postulate was confirmed by reisolation of the pathogen from experimentally induced disease lesions. By contrast, pathogenicity tests with one endophyte species failed to elicit disease symptoms. We describe two new species of generalist endophytes, C. tropicale and C. ignotum, which frequently associate with cacao, and epitypify C. theobromicola, a foliar and fruit pathogen of cacao.