Biblioteca do Café
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Item Isolates of Aspergillus, Clonostachys and Trichoderma from Africa as potential biocontrol agents against coffee leaf rust(Universidade Federal de Viçosa, 2022-03-14) Kapeua Ndacnou, Miraine; Barreto, Robert WeingartHemileia vastatrix – the coffee leaf rust (CLR) fungus – is native from Africa and an exotic invasive species in all other areas of the world where coffee is grown. It causes the worst disease of coffee, but in Africa, it is not regarded as the worst pathogen of the crop. Management of CLR has relied on escaping the disease through the highland plantation, using resistant coffee varieties and fungicide applications. There are limitations for each of these strategies and novel approaches for CRL management are necessary. It has been conjectured that natural enemies of H. vastatrix endemic to Africa might have been overlooked and that such antagonists might have the potential for CLR management. Surveys conducted since 2015 in Cameroon, Ethiopia and Kenya, have revealed numerous mycoparasitic fungi attacking CLR in the field as well as endophytic fungi growing inside healthy coffee plants (several of which were, or are being, described as new to science), which might play a bodyguard role, protecting the plants against the disease. Results of previous studies and of the present research seem to confirm this hypothesis. A series of taxonomic and polyphasic studies allowed to identify isolates of Aspergillus and Clonostachys as belonging to Aspergillus flavus, Clonostachys byssicola, C. rhizophaga and C. rosea f. rosea. All the selected endophytic isolates (confirmed here regardless of the genus, to grow as endophytes in coffee), including Trichoderma strains were demonstrated to inhibit the germination of H. vastatrix in vitro. The isolate of A. flavus was shown not to produce aflatoxin. Beforehand applications of a series of isolates, of Clonostachys, Trichoderma and also of A. flavus, on young C. arabica plants (a combination of soil and foliar applications) followed by inoculation with H. vastatrix led to the significant reductions in CLR severity. Two Clonostachys rhizophaga isolates (COAD 2981 and COAD 2982), and one C. rosea isolate (COAD 2984) yielded the best highly significant (p < 0.001) results for reduction of CLR severity among the Clonostachys isolates. Trichoderma guizhouense (COAD 2398), T. virens (COAD 2400) and T. theobromicola (COAD 2406) also produced highly significant (p < 0.001) levels of CLR severity reduction. This is the first study reporting anti-CLR biocontrol potential for African isolates of A.flavus, Clonostachys and Trichoderma. And, they may pave the way towards preventive treatment of coffee plants with ‘bodyguard’ endophytes antagonistic to H. vastatrix as well as their use for control of CLR in the field. A continuation of this work is required to better assess this possibility. Keywords: Classical biocontrol. Coffee rust. Endophytes. Phylogeny. Taxonomy.