Seed health tests of traditional leafy vegetables and pathogenicity in plants

Traditional leafy vegetables play a significant role in the daily diets of many people in Zimbabwe. They are produced by smallholder farmers with limited knowledge on the agronomic value of high-quality seed, on seed storage, and on plant- and seed-borne pathogens. The quality of the seed is rarely tested for seed-borne pathogens posing risks of pathogen build-up. This study was conducted in order to determine the seed-borne pathogens associated with traditional leafy vegetable seeds. Seeds were collected from five different farmers in three provinces of Zimbabwe and tested for the presence of pathogens in the plant pathology laboratory of the University of Zimbabwe. A total of 154 fungal and 233 bacterial infections were recorded on 450 seeds for each type of pathogen. Significantly high percentages of the isolates (Xanthomonas campestris, Curvularia spp., Alternaria alternata, Fusarium oxysporum and Pseudomonas syringae) were obtained from the three different species of traditional leafy vegetables (Amaranthus hybridus, Bidens pilosa and Cleome gynandra). F. oxysporum, A. alternata, X. campestris and Bacillus spp. isolates were pathogenic to traditional leafy vegetable plant species as confirmed by pathogenicity tests, hence may have significant effects on traditional leafy
vegetables production. The results indicate that seed sourced from farmers 1, 2, 3 and 4 resulted in seed-borne pathogens on both the seed and plants, clearly showing that seed quality was poor. Although most pathogens observed have a broad host spectrum, pathogenicity and virulence tests confirmed that some pathogens were likely to be closely associated with these traditional leafy
vegetable seed species.