Identificação e caracterização de bactérias com potencial para controle biológico

Abstract

Biological control through the use of microorganisms is an alternative to reduce the use of pesticides in the control of plant pathogens, which affect plants of agricultural interest. In this context, the objective of this work was to identify and quantify the inhibition potential of previously selected bacteria against phytopathogenic fungi. Eight microorganisms were evaluated: three endophytic isolates obtained from guaranazeiro roots (PcA1, PcA2, PcA3)) and five isolates from Madeira River sediments, from these four actinobacteria (MAD 24, MAD 42, MAD 51 and MAD 189). bacteria (MAD 207)). These were identified by morphomolecular analysis based on scanning electron microscopy and 16S rDNA region sequencing data. Inhibition potential (PIC) against four phytopathogens: Colletotricum siamense, Pseudopestalotiopsis gilvanis sp. nov., Neopestalotiopsis formicarum and Fusarium decemcellulare, were obtained in vitro using the double culture methodology in BDA medium. The mean percentage inhibition (PIC) after 10 days ranged from 46% to 74% depending on the bacteria tested. The isolates PcA1, PcA2, PcA3 and MAD207 performed better against F. decemcellulare (71% ± 2.8, 64% ± 1.7, 72 ± 4.5 and 78% ± 1, respectively). The MAD24 isolate showed better performance against N. formicarum (72% ± 0.5), MAD42 and MAD51 against C. siamense (72% ± 0.5; 74% ± 2.4), and MAD189 against N. formicarum (69% ± 0.5). PcA1, PcA2, PcA3 and MAD207 isolates were identified, based on sequence analysis of the 16S rRNA gene, as members of the Bacillus genus, which were phylogenetically related to B. amyloliconefaciens, B. subtilis, B. nakamurai and B. velezensis respectively. . Scanning electron microscopy data revealed different morphology for each isolate, suggesting that they belong to different species. Isolates MAD24, MAD42, MAD 51 and MAD189 were identified as members of the genus Streptomyces. Samples MAD189 and MAD42 were more phylogenetically related to each other and formed a separate clade, MAD51 showed low phylogenetic relationships with the analyzed species and MAD24 was grouped in the constraricanus clade, S. griseofuscusmurinus. The morphological data corroborate the molecular inferences and differences in size and shape were identified in all isolates.. Keywords: Actinobacteria; Antimicrobials; Biological control.