Diversity of fungal and fungi-like pathogens of tomato (solanum lycopersicum) from selected parts of Lusaka province.
Date
2023
Authors
Mweemba, Godfrey
Journal Title
Journal ISSN
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Publisher
The University of Zambia
Abstract
Fungal and fungi-like pathogens including Cladosporium fulvum, Alternaria alternate, and Alternaria solani class dothideomycetes are major pathogens of solanaceous crops such as tomato (Solanum lycopersicum) where they cause significant losses. To contribute to the understanding
of the extent to which fungal pathogens affect tomato productivity in a major tomato-growing part of Zambia, the study tested the hypothesis that various fungal and fungi-like pathogens are circulating in tomato-growing areas of Lusaka and show morphological, molecular and virulence
diversity. Tomato tissue showing diverse disease symptoms including leaf spotting, stem rotting and fruit damage were collected from farmers’ fields in various parts of Lusaka Province. Surface-sterilised tissue was cultured on potato dextrose agar to analyse the morphological diversity of isolates.
Purified isolates were used in infection studies to fulfill Koch’s postulates and to analyse the variations in virulence of the isolates. Genomic DNA was extracted from the purified fungal isolates and PCR-amplified using primers targeting the internal transcribed spacer region (ITS). The Sanger dideoxy chain termination sequencing method was used to sequence the PCRamplified genomic DNA. Taxonomic identification of isolates from this study indicate that Alternaria alternata, Epicoccum nigrum and Cladosporium fulvum are some of the tomato pathogens circulating in the study area showing diversity in virulence and morphological characteristics. Selected isolates were found to have varying levels of virulence on Tengeru tomato variety. From 20 plants whose leaves were inoculated with pathogens from each study site, the means lesion diameters were found to be 5.9mm for samples from University of Zambia agriculture research field, 8.29mm for isolates from 13Miles and 6.095mm for those from Kafue. Molecular phylogeny analysis of the sequenced ITS amplicons by the maximum likelihood criterion revealed relatedness between isolates from similar regions of the study area as well as those from various regions of the study area. Results from this study will be useful for tomato breeders and farmers as they conduct breeding projects and use fungicides to control the pathogens circulating in the study area.
Description
Thesis of Master of Science in Molecular Biology.