Efeito in vitro de Saccharomyces cerevisiae sobre Guignardia citricarpa, agente causal da pinta preta dos citros. / In vitro effect of Saccharomyces cerevisiae on Guignardia citricarpa, causal agent of citrus black spot.

AUTOR(ES)

Mauricio Batista Fialho

DATA DE PUBLICAÇÃO

2005

RESUMO

Due to the consumers perception about the impact caused by pesticides utilization over the environment and human health, besides the acquisition of resistance for part of the phytopathogens, the society has exercised pressures that had led to the establishment of governmental politics that restrict the use of fungicides leading agriculturists and researchers to consider the application of techniques of biological control of plant pathogenic fungi. Guignardia citricarpa is the causal agent of citrus black spot that has a great economic importance, therefore interfering in production and causing aesthetic depreciation of the fruits that can interfere with commercialization of fresh-fruit in the external market. In this context, the aim of this work was to evaluate in vitro the potential of Saccharomyces cerevisiae strains, used in fermentative process, as biocontrol agents against G. citricarpa. Through plate assay it was evidenced that among the tested strains of S. cerevisiae (BG-1, CR-1, CAT-1, KD-1, K-1 and PE-2), the strain CR-1 was the one that demonstrated the greatest antagonic activity against the phytopathogen, causing 73% of micelial growth inhibition. It was also demonstrated that the strains were able to produce volatile compounds with fungistatic action inhibiting up to 83% the development of the pathogen. The autoclaved and not autoclaved culture filtrate, as well as the termical inactivated cell obtained from the growth of strain CR-1 in YEPD medium for 24 h, did not cause reduction in the fungal vegetative growth. The production of extracellular hydrolytic enzymes (chitinases, β-1,3-glucanases and proteases) by the yeast was not detected in YEPD medium with glucose or cell wall preparation of G. citricarpa at the evaluated times. Based upon the obtained information it was possible to evidence that the strains of S. cerevisiae, specially the strain CR-1, are potentials antagonists for the control of G. citricarpa. The possible mechanism used for inhibition by yeast is the volatile production, however other mechanisms cannot be discarded. Thus, the present work shows the potential of S. cerevisiae to control G. citricarpa in orange fruits in postharvest.

ASSUNTO(S)

fungo fitopatogênico pathogen mancha-preta-dos-citros yeast biological control orange phytopathogenic fungi citrus black spot levedura laranja controle biológico antagonista antagonist patógeno

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