Potencial de Penicillium citrinum para o controle de Aspergillus niger, agente causal da podridão vermelha do sisal

Abstract

Sisal (Agave sisalana Perrine) production for fiber extraction represents an important economic sector for the Northeastern region of Brazil. However, problems such as sisal red rot disease, caused by Aspergillus niger, have caused a decline of this crop. Amongst the strategies for plant disease control, biological control with the use of antagonistic micro-organisms has been pointed out as a viable method. In this study, the potential of Penicillium citrinum isolated from sisal plants of the semiarid region of Bahia State, in Brazil, was evaluated for control of sisal red rot disease. Penicillium citrinum was identified by using morphological and molecular techniques. Tests of antagonism in CYA and PDA culture media showed that P. citrinum inhibits mycelium growth of A. niger, showing the highest percentage of inhibition (65.76%) on CYA medium, when the pathogen was introduced 72 hours after incubation of CYA medium with P. citrinum. In vitro tests with sisal stem tissue discs, demonstrated highest pathogen inhibition rates for time intervals of fungal inoculation greater than 48 hours. P. citrinum colonizes internal sisal root and stem tissue approximately five days after inoculation. This fungus is not pathogenic to sisal plants and can control up to 100% sisal red rot disease, when inoculated in plants, at least 24 hours before pathogen inoculation. A. niger showed poor ability to survive in soils from sisal plantations, while the population of P. citrinum appeared to be more stable under these conditions, and also, was shown to be effective in reducing the population of A. niger in soil. The metabolites of P. citrinum were effective in inhibiting spore germination of A. niger. In PDA culture medium, 75% of medium with fungal metabolites provided the greatest reduction rate of A. niger mycelium growth. It is concluded that P. citrinum presents the potential to control sisal red rot disease.