Abstract
<p>Saprobe fungi and necrotrophic pathogens share the same niche within crop stubble and the search for fungi non-pathogenic to plants that are able to displace the plant pathogens from its overwintering substrate contributes to the disease management. Brown eye spot (<em>Cercospora coffeicola</em>) is among the most important coffee diseases, it is caused by a necrotrophic pathogen that has decaying leaves as its major source of inoculum. We have screened saprobe fungi for the ability to reduce <em>C. coffeicola</em> sporulation and viability and determined the possible mechanisms involved in the observed biocontrol. A selected saprobe fungus, <em>Phialomyces macrosporus</em>, reduced the pathogen’s viability by 40% both <em>in vitro</em> and <em>in vivo</em>. The fungus acts through antibiosis and competition for nutrients. It produced both volatile and non-volatile compounds that inhibited <em>C. coffeicola</em> growth, sporulation, and viability. It also produced the tissue maceration enzyme (polygalacturonase), which reduces the pathogen both in detached leaves or in planta. The reduction in the fungal viability either by the saprobe fungus or its polygalacturonase-fraction supernatant resulted in the reduction of the disease rate. Therefore, <em>P. macrosporus </em>is a potential microbial agent that can be used in an integrated management of brown eye spot through the reduction of the initial inoculum of the pathogen that survives and builds up in infected leaves.</p><p> </p>
Highlights
Coffee (Coffea arabica L.) is an important commodity worldwide
Effective fungicide-based alternatives are available for the disease management (Patricio et al, 2008), it should not be the exclusive tool but part of the integrated brown eye spot management such as plant nutrition (Cardoso et al, 2013) and biological control (Sirinunta and Akarapsan, 2015)
The effect of toxic molecules or enzyme produced by P. macrosporus on C. coffeicola was quantified by comparing the mycelia growth and number of conidia
Summary
Coffee (Coffea arabica L.) is an important commodity worldwide. diseases are responsible for many losses in this crop. Brown eye spot (BES), caused by the necrotrophic fungus Cercospora coffeicola Berkeley & Cooke is considered one of the most important coffee diseases and affects both leaves and berries, causing yield losses of approximately 50% (Zambolim et al, 2016). Conditions for germination, the reduction of the initial inoculum should be taken into account as a strategy for the integrated management of the disease This can be achieved by compostaccelerating products which encompasses both fast-growing fungi and cell wall degrading enzymes (Bellotte et al, 2009; Hauptman, 2014). Competition for nutrients is likely to occur since hydrolytic enzymes produced by both pathogen and antagonist target the saprophytic survival on decaying leaves (Jurado et al, 2015; Alvarez-Rodriguez et al, 2016) Among these enzymes are pectinases, which are composed by an heterogeneous group of enzymes that degrades pectin (Falmy et al, 2008). We hypothesize that saprobe fungi might inhibit C. coffeicola growth in crop residues and its production antifungal compounds and cell-wall degrading enzyme may play a role in the pathogen displacement
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