Ecological speciation through host-shift has been proposed as a major route for the appearance of novel fungal pathogens. The growing awareness of their negative impact on global economies and public health created an enormous interest in identifying the factors that are most likely to promote their emergence in nature. In this work, a combination of pathological, molecular and geographical data was used to investigate the recent emergence of the fungus Colletotrichum kahawae. C. kahawae emerged as a specialist pathogen causing coffee berry disease in Coffea arabica, owing to its unparalleled adaptation of infecting green coffee berries. Contrary to current hypotheses, our results suggest that a recent host-jump underlay the speciation of C. kahawae from a generalist group of fungi seemingly harmless to coffee berries. We posit that immigrant inviability and a predominantly asexual behaviour could have been instrumental in driving speciation by creating pleiotropic interactions between local adaptation and reproductive patterns. Moreover, we estimate that C. kahawae began its diversification at <2200 bp leaving a very short time frame since the divergence from its sibling lineage (c. 5600 bp), during which a severe drop in C. kahawae's effective population size occurred. This further supports a scenario of recent introduction and subsequent adaptation to C. arabica. Phylogeographical data revealed low levels of genetic polymorphism but provided the first geographically consistent population structure of C. kahawae, inferring the Angolan population as the most ancestral and the East African populations as the most recently derived. Altogether, these results highlight the significant role of host specialization and asexuality in the emergence of fungal pathogens through ecological speciation.
Coffee Berry Disease, caused by Colletotrichum kahawae, is a major limitation for Arabica coffee cultivation in Africa and for which genetic control is only partially effective. As part of the effort to re-launch coffee cultivation in Angola, our aim was to study the diversity of this pathogen and so contribute to more effective breeding for disease resistance. A collection of 30 C. kahawae isolates showed limited diversity in genetic and colony characters. However, some isolates are distinct, suggesting that breeding for disease resistance in Angola should be dependent on an adequate knowledge of the diversity of local and neighbouring C. kahawae isolates. Analysis of C. kahawae nrDNA nucleotide sequences showed distinct lineages clustering within the broad diversity of C. gloeosporioides, prompting further studies aimed at understanding the origin and pathogenic specialization of C. kahawae.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.