Fungi associated with a dry invasive white patches on trunks of economic fruit trees in south-west Nigeria

Abstract

An unprecedented number of fungal and fungal-like diseases are the main threat to the diversity and productivity of economic fruit trees in south-west Nigeria. The objective of this study was to investigate the fungi associated with dry invasive whitish patches, noticeable on trunks and branches of cocoa (Theobroma cacao), kola-nut (Cola spp.) and sweet orange (Citrus sinensis) trees prevalent in south-west Nigeria. A total of 108 whitish patch scraped samples were aseptically obtained from the affected cocoa, kola-nut and sweet orange trees in Osogbo, Ife, Ejigbo and Ilesha plantations in south-west Nigeria for this study. Viable fungal populations, were determined using the spread-plate techniques; and pure fungal isolates were identified through their morphological appearance, microscopic features and sporing structures. Mean viable fungal count in the samples ranged from 3.85 x 104 ± 0.00 to 9.75 x 103 ± 0.00 CFU g-1. Viable fungal counts were significantly different (P < 0.05) between fruit tree species and across locations. A total of 52 fungal species belonging to 21 genera were isolated, with Aspergillus and Penicilliumas predominating and occurring at 23 and 17%, respectively. Other isolated genera included seven from cocoa trees; ten from kola-nut trees and five from sweet orange trees. There is need for appropriate control strategies to prevent further spread in contiguous plantations.

Key Words: Aspergillus, kola-nut, sweet orange, Theobroma cacao