Uncovering the Fusarium community associated with Hemileia leaf rusts and coffee from Africa and South America

A survey of fungi found overgrowing and colonizing pustules of coffee leaf rusts, caused by species of the genus Hemileia, and also occurring as endophytes of Coffea, was conducted in Africa (Cameroon-Ca and Ethiopia - Et) and South America (Brazil - Br and Paraguay-Pa). Among the significant groups of fungi collected as putative mycoparasites of Hemileia, 93 isolates belonged to the genus Fusarium and Neocosmospora. Eight Fusarium coffee endophyte isolates were independently obtained from Brazil and added to the assemblage of isolates. A polyphasic taxonomic study was conducted involving cultural and morphological features, multigene phylogenetic analyses plus information on rust host species and geographic distribution. As a result, the isolates were found to belong to three Fusarium species complexes (Fusarium sambucinum species complex, Fusarium incarnatum-equiseti species complex and Fusarium lateritium species complex). Nine isolates belonged to Neocosmospora (formerly known as Fusarium solani species complex). The vast majority of the isolates fell within the F. lateritium species complex. The assemblage of isolates obtained in the survey included three known taxa, namely: Fusarium citri (Br, Et, Pa), Fusarium coffeibaccae (Br, Ca, Et) and Neocosmospora perseae (Ca, Et). Two new species of Fusarium were also obtained and are described herein: Fusarium hemileiae sp. nov. (Br) and Fusarium hemileicola sp. nov. (Et). None of these species had ever been reported from coffee leaf rust pustules. The most common and widespread taxon in our survey was F. coffeibaccae. The latter was observed here to be a putative mycoparasite of Hemileia spp. and also, the sole species belonging to the assemblage which was regularly isolated as an endophyte from healthy tissues of coffee. The present study provides the taxonomic background for an ongoing evaluation of these putative mycoparasites and endophytes as potential biocontrol agents to be deployed against Hemileia rusts of coffee.