The endophytobiome of wild Rubiaceae as a source of antagonistic fungi against the American Leaf Spot of coffee (Mycena citricolor)

Abstract

Aims The American leaf spot, caused by Mycena citricolor, is an important disease of coffee (Coffea arabica), mostly in Central America. Currently, there are limited pathogen control alternatives that are environmentally friendly and economically accessible. The use of fungi isolated from the plant endomycobiota in their native habitats is on the rise because studies show their great potential for biological control. To begin to generate a green alternative to control M. citricolor, the objectives of the present study were to (i) collect, identify, screen (in vitro and in planta), and select endophytic fungi from wild Rubiaceae collected in old-growth forests of Costa Rica; (ii) confirm endophytic colonization in coffee plantlets; (iii) evaluate the effects of the endophytes on plantlet development; and (iv) corroborate the antagonistic ability in planta. Methods and results Through in vitro and in planta antagonism assays, we found that out of the selected isolates (i.e., Daldinia eschscholzii GU11N, Nectria pseudotrichia GUHN1, Purpureocillium aff. lilacinum CT24, Sarocladium aff. kiliense CT25, Trichoderma rifaii CT5, T. aff. crassum G1C, T. aff. atroviride G7T, T. aff. strigosellum GU12, and Xylaria multiplex GU14T), Trichoderma spp. produced the highest growth inhibition percentages in vitro. Trichoderma isolates CT5 and G1C were then tested in planta using Coffea arabica cv. caturra plantlets. Endophytic colonization was verified, followed by in planta growth promotion and antagonism assays. Conclusions Results show that Trichoderma isolates CT5 and G1C have potential for plant growth promotion and antagonism against Mycena citricolor, reducing incidence and severity, and preventing plant mortality.

Differential Volatile Organic Compound Expression in the Interaction of Daldinia eschscholtzii and Mycena citricolor

“…citricolor (isolate LAMYH1) was recovered from infected coffee plants from San Marcos de Tarrazu, Costa Rica. Both isolates were identified and used in a previous study by our research team . Both fungi are preserved at −80 °C in cryovials with 20% glycerol and in sterile water at room temperature (∼25 °C) in CIPRONA (University of Costa Rica) culture collection.…”

“…For example, in a recent study, several species of endophytes from wild Rubiaceae plants from Costa Rica were effective against M. citricolor in vitro and in planta, reducing disease incidence and severity and promoting plant growth . However, that study hinted only at potential mechanisms of fungicidal or fungistatic effects.…”

“…Among the isolates studied by Escudero-Leyva et al, 34 Daldinia eschscholtzii GU11N, obtained from the plant Randia grandifolia (Rubiaceae), had an antagonistic effect over M. citricolor in an in vitro dual culture experiment. In that study, antibiosis was hypothesized as the mechanism of antagonism.…”

“… 33 For example, in a recent study, several species of endophytes from wild Rubiaceae plants from Costa Rica were effective against M. citricolor in vitro and in planta, reducing disease incidence and severity and promoting plant growth. 34 However, that study hinted only at potential mechanisms of fungicidal or fungistatic effects. Understanding those mechanisms against pathogens, with specific interest in the release of metabolites possessing protective capabilities for essential crops, could lead to the development of effective alternatives for disease control.…”

Agricultural practices influence foliar endophytic communities in coffee plants of different varieties

“…For the culture-dependent approach, the procedures described in Escudero-Leyva et al (2023) were used. Briefly, five segments from each leaf (including lamina tip and base, midrib, and left and right margins) were cut and surface-sterilized in accordance with the previously described immersions to remove external contaminants (e.g., epiphytic microbes).…”