Antimicrobial activity of Ocimum gratissimum L. and Carica papaya L. against postharvest pathogens of avocado pear (Persea americana Mill.)

Abstract

Phytopathogenic fungi associated with postharvest rot of avocado pear were isolated and identified. The identification was based on their morphological and microscopic characteristics. The effects of ethanolic plant extracts of Ocimum gratissimum L. and Carica papaya L. on in vitro inhibition of the mycelia growth of the isolates were determined. The isolates were identified as Aspergillus niger, Aspergillus flavus, Galactomyces candidum, Trichoderma viride, Rhizopus delemar and Lasiodiplodia pseudotheobromae and were confirmed by pathogenicity test as the causal agents of fungal rot of avocado pear. The extracts inhibited the mycelia growth of the pathogens except R. delemar, to a significant level (P < 0.05) at different concentrations of 20, 40, 60, 80 and 100 mg/ml. The inhibitory effects of the plant extracts increased with increase in concentration. The fungicidal activity was strongly exhibited by O. gratissimum at 100 mg/ml against all the pathogens except R. delemar which showed no inhibition at all concentration. Carica papaya extract was more effective against A. flavus with inhibitory effects of 38.45 ± 5.18, 30.40 ± 1.85 and 21.47 ± 3.24% at 80, 60 and 20 mg/ml concentration, respectively. The inhibitions were significantly different at P < 0.05. It could be concluded that the plant extracts can effectively control fungal rot of Persea americana Mill and as such potential biofungicide for the management of postharvest losses.