FIGURE

Prelecionista: Dra. Thaisa F. Nóbrega. Data: 01/06/2021, às 16:00 horas pelo ZOOM*. Orientador: Robert W. Barreto.

Coffee leaf rust (CLR) is the main disease that affects cultivated Coffea spp., causing great damage in all producing regions of the world. It is caused by the fungus Hemileia vastatrix. CLR is mainly controlled by the application of chemical fungicides, the planting of resistant cultivars and the escape through highland cultivation. Nevertheless, outbreaks have started in Northern South America and Central America since the early 2010s because of problems with the three management strategies. This highlighted the need for new management approaches. Biological control with antagonistic fungi is a possible alternative. The results on a study concentrated on isolates of Fusarium spp. collected from colonized CLR pustules in Brazil and Paraguay, but more focused, for the first time, on isolates obtained from the native region of H. vastatrix and cultivated Coffea spp. in Africa (Cameroon and Ethiopia) are reported here. The taxonomy of putative mycoparasitic Fusarium isolates obtained during the surveys was elucidated and a preliminary screening was conducted in order to test their potential against CLR in vitro and in planta. The polyphasic taxonomic study revealed seven distinct species (belonging to four different species complex). Four of those species are being described as new to science. More than 80% of the isolates were characterized as belonging to Fusarium sp. nov. 1 – a member of the Fusarium lateritium species complex (FLSC). In in vitro tests, 17 isolates reduced the severity of CLR by more than 80% in three application time-regimes. Three isolates of Fusarium sp. nov. 1 (COAD 3011, COAD 3041 and COAD 3065) completely controlled the disease and were selected for further testing. Preventive applications of conidial suspensions of the three selected isolates on plants were efficient at reducing CLR severity (up to 70%) in the greenhouse. Control levels attained were superior to preventive copper fungicide treatment. Applications of Fusarium sp. nov. 1 culture filtrates from two isolates (COAD 3011 and COAD 3065) also significantly reduced CLR severity. In planta applications of conidial suspensions and filtrates after pustule formation did not prevent or reduce CLR progress. However, in parallel it was observed that applications of COAD 3041 conidial suspension, stopped the germination of the majority of the urediniospores of H. vastatrix or led them to produce aberrant germ tubes. Future research may confirm whether one or more among the “elite isolates” of Fusarium sp. nov. 1 have the potential to be uses as an anti-CLR treatment for the benefit of coffee farmers, consumers and the environment.

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