Cultivable root endophytic fungi associated with Acrocomia aculeata and its antagonistic activity against phytopathogenic oomycetes.

Macaw palm (Acrocomia aculeata Jacq.) is a palm, native to Brazilian territory that stands out due to the amount of oil produced with applications in the biodiesel industry, cosmetics, and food. Its commercial exploitation in Brazil, including phytosanitary management is based on concepts and practices of regenerative agriculture, which has the responsibility of sustainable cultivation by avoiding, for example, the use of chemical pesticides. Recently, root and stem rot disease were reported in macaw palm seedlings caused by Phytophthora palmivora. Managing this plant pathogen is complex, and the chemical control of this soil-borne oomycete is not viable, in addition to the negative impact on the environment. Many microorganisms are studied and used as biological control agents (BCAs) against pathogens, among them the community of endophytic fungi associated with plants. This is a sustainable biotechnological alternative for plant disease control. The community of cultivable endophytic fungi associated with healthy roots of macaw palm was explored using the extinction cultivation technique and a screening was carried out to select potential antagonists against oomycetes through the dual culture test. Specific gene regions from the best isolates were amplified for identification. A total of 250 isolates were obtained, and 46 were selected for in vitro tests against representatives of phytopathogenic oomycetes. After tests against Phytophthora heterospora, Phytophthora palmivora, Pythium aphanidermatum, and Pythium deliense, two isolates were selected as potential antagonists. The phylogenetic analysis of selected isolates showed that they belong to two different species: Talaromyces sayulitensis COAD 3605 and Epicoccum italicum COAD 3608. The percentage of inhibition of phytopathogenic oomycetes testedwas until 82% in the antagonism tests conducted. From the 46 isolates selected, only 2 were selected which showed great antagonistic activity towards all oomycetes tested. These fungi will be used in upcoming studies that aim to determine the effectiveness of endophytes in controlling diseases caused by oomycetes in the field.