Antimicrobial Activities of Endophytic Fungal Crude Extracts Isolated from Cashew Tree (Anacardium occidentale)

Abstract

This study presents the antimicrobial activities of endophytic fungal crude extracts isolated from leaves, stems and roots of cashew trees (Anacardium occidentale) which showed disease symptoms and those resistant from Fusarium wilt in Mtwara region. Sections of the cashew trees were made and cultured to isolate endophytes. Eight endophytes were isolated and characterized by using morphological and molecular markers. Neopestalotiopsis, Penicillium, Lasidioplodia and Daldinia sp isolated from resistant tree and Auxarthron and Aspergillus sp from diseased tree. Antimicrobial activities of the isolated endophytic fungal crude extracts were done against pathogenic Fusarium oxysporum and three human pathogens namely, Staphylococcus aureus, Escherichia coli, and Candida tropicalis. Results showed that all endophytic fungal crude extracts isolated from resistant plants and one from diseased plants exhibited positive antimicrobial activities against bacteria and fungus Candida tropicalis but they had no antifungal activity against Fusarium oxysporum. This study could contribute to the discovery and innovation of therapeutics. This study also implied that the resistance against Fusarium wilt disease might be caused by other unknown factors. More research work is recommended for establishing other possible factors including endophytic bacteria, biotic and abiotic factors that could contribute to resistance of cashew plants to Fusarium oxysporum.
 Keywords: Antifungal; Phytopathology; Endophyte; Cashew nut disease

Disease-Causing Agents in Cashew: A Review in a Tropical Cash Crop

“…Reports on Cryptosporiopsis, which causes cashew blight disease infecting mainly the apple and nuts, were restricted to Tanzania (n = 8), with a high potential to decrease cashew productivity [47]. The Fusarium genus represented by a single species (F. oxysporum) was associated with root rot disease [63] and, more recently, with Fusarium wilt disease (FWD) in Tanzania [15], which mainly affects the leaf and root/stem and ultimately leads to complete wilting of the cashew canopy and tree death [64]. Our study showed that F. oxysporum occurs in Tanzania (East Africa), Nigeria (West Africa), India, and Indonesia.…”

“…Despite previous reports of root rot disease in Nigeria in 1974 [65] and afterward in Indonesia [63] and India [66], few studies highlighted F. oxysporum as a major pathogen in cashew. Nevertheless, due to the alarming scenario described in recent works from Tanzania [64], where cashew orchards have been devastated by FWD, cashew-producing countries should be vigilant regarding possible future infections by this pathogen. Indeed, due to the lack of proper disease-screening trials in cashew-producing countries, Fusarium should not be discarded as a minor pathogen and remains to be identified at the species level.…”