Evaluation of the pathogenic effect of some fungal isolates on fruits and seedlings of pepper (Capsicum spp)

Abstract

Laboratory and screenhouse experiments were carried out to identify and establish the pathogenic status of the micro-organisms isolated from the diseased fruits, stems and leaves of naturally infected pepper plants (Capsicum spp) on a devastated field cropped to assorted vegetables during the latter part of the rainy season of 2003 in Ilorin, Nigeria. Pure cultures of several fungal species were isolated on Potato Dextrose Agar (PDA). The consistently isolated fungi from the fruits and seeds were identified as Penicillium digitatum, Aspergillus flavus and Aspergillus niger while a specie of Verticillium was isolated from the leaves and stems. Pathogenicity tests on fresh pepper fruits in –vitro revealed that all the fungal isolates were pathogenic on the two pepper species (Capsicum annuum and C. frutescens) tested in this study. Level of susceptibility and or virulence however differed as measured in the ability of the fruit to support the growth of the fungi and subsequent development of fruit rot. Penicillium digitatum was the least virulent while Aspergillus niger was the most virulent. Pathogenicity test in the screenhouse showed that foliar inoculation of Verticillium sp on four -week old pepper seedlings induced strong symptom response in the form of initial necrotic spots on the leaves and then eventual wilting and dying -off of the seedlings after 4 weeks of inoculation. No fruits were produced on such diseased plants compared to the mock-inoculated control plants. The three other fungi isolates did not induce any visible infection on the seedlings indicating that the Verticillium sp was responsible for the wilting and drying off observed on the field pepper plants.

Keywords: Aspergillus niger, A. flavus, Penicillium digitatum, Verticillium spp, Capsicum annuum, and C. frutescens, fruit rot and wilting.

JARD Vol. 4 (2) 2005: pp. 159-169