Abstract
Digitopodium hemileiae was described originally in 1930 as Cladosporium hemileiae; growing as a mycoparasite of the coffee leaf rust (CLR), Hemileia vastatrix, in a sample of diseased leaves of Coffea canephora collected in the Democratic Republic of Congo. No cultures from this material exist. More recently, the type material was re-examined and, based on morphological features, considered to be incorrectly placed in Cladosporium. The new genus Digitopodium was erected to accommodate this species. Interest in fungal antagonists of H. vastarix, as potential biocontrol agents of CLR, led to comprehensive surveys for mycoparasites, both in the African centre of origin of the rust, as well as in its South American exotic range. Among the rust specimens from Ethiopia, one was found to be colonized by a fungus congeneric with, and similar to, D. hemileiae. Pure cultures obtained from the Ethiopian material enabled a molecular study and for its phylogenetic position to be elucidated, based on DNA sequence data from the ITS and LSU regions. Molecular data showed that two members of the recently erected genus Hyalocladosporiella (Herpotrichiellaceae: Chaetothyriales) are congeneric with Digitopodium from Ethiopia and morphologically similar to both D. hemileiae and the two Ethiopian isolates. These isolates were found to be morphologically and genetically identical to H. tectonae, described previously from Brazil. Thus, species of Hyalocladosporiella are re-allocated to Digitopodium here; including D. tectonae, and a novel species, D. canescens, recently found in Brazil growing as a mycoparasite of Puccinia thaliae. The potential use of D. hemileiae and D. tectonae for classical biological control of CLR is discussed.
Highlights
Hemileia vastatrix is the most important pathogen of coffee plants worldwide, causing coffee leaf rust (CLR) (Zambolim 2016, Talhinhas et al, 2017)
The phylogenetic analysis indicated that members assigned to Digitopodium do not belong in the Cladosporiaceae
The combination of the morphological evidence and the results of the molecular analysis (Fig. 1), led to the recognition that Hyalocladosporiella represents a younger, heterotypic synonym for Digitopodium, differences in the characteristics of the conidia in the Ethiopian collection to the type of D. hemileiae indicated that these represent a separate species
Summary
Hemileia vastatrix is the most important pathogen of coffee plants worldwide, causing coffee leaf rust (CLR) (Zambolim 2016, Talhinhas et al, 2017). Efforts in mitigating the impact of CLR have included a pioneering initiative towards the development of a classical biological control management strategy, based on the use of fungal natural enemies from the native range of coffee and Hemileia vastatrix in Africa. A number of mycoparasitic fungi of CLR have been reported previously (Carrion & Rico-Gray 2002, James et al 2016). The latter records are all from the (2021) 12:1. Americas, where coffee and H. vastatrix are exotic species. Such mycoparasites are interpreted, as generalists that have jumped from other fungal hosts and did not co-evolve as specialized parasites of the CLR fungus. This publication deals with a reappraisal of the taxonomy of D. hemileiae and related taxa, based on newly-collected specimens obtained during surveys for mycoparasites of H. vastatrix in Africa and of related material collected in Brazil
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