BIOASSAY AND RESPONSE OF PYRETHRUM (Chrysanthemum cinareriifolium) GENOTYPES TO PATHOGENIC FUNGI IN KENYA

Abstract

Fungal pathogens are a major production constraint to quantity and quality of pyrethrin in Kenya and other parts of the world. Pyrethrin is a natural insecticide that is cheap, environmentally friendly, acts with celerity, less harmful to both animals and humans and also can be used against a wide range of insects and because of the above importance of pyrethrum and the problem of fungal diseases as a constraint to higher production of the crop, this study was carried out with the following objectives; 1) To assess the morphological diversity and frequency of isolation of the major fungal pathogens affecting pyrethrum production in Kenya, 2) To assess the pathogenicity of identified fungal isolates and response of selected genotypes under greenhouse conditions and 3) To determine the efficacy of selected control agents in management of identified fungal pathogens in vitro and therefore, A field visit to major pyrethrum growing zone Nakuru county, was done and infected plant parts with symptoms of fungal infection were sampled and taken to laboratory for analysis. Isolation and identification was done and after identification pathogens with higher isolation frequencies were tested for their pathogenicity and virulence on five pyrethrum genotypes Clone 1 - 4 and P4 in an experiment set in split plot arrangement in CRD with genotypes as main plots and isolates as subplots replicated three times. Data on incidence and severity were scored after inoculation at an interval of 14 days using severity scales. Most virulent pathogens were further selected and taken to the laboratory for testing inhibitory efficacies of selected control agents where a split plot arrangement in CRD was set with isolates as main plots and control agents as sub plots replicated thrice. Agar dilution method and dual culture method were used to test control agents and data on mycelial growth inhibition were scored. Results indicate that there was diversity in fungal pathogens isolated from plants showing symptoms of bud disease, pyrethrum wilt and crown rot disease. There was a significant difference in the pathogenicity and response of selected isolates as p <0.05. All the isolates tested were pathogenic and Clone 4 was more tolerant to most fungi. Botanicals showed promising results as garlic performed well like Carbendazim in the in vitro reactions with the test fungi. Selected Trichoderma species displayed antifungal properties against all the test fungi. These results indicate that fungal pathogens are still a problem in farmers’ fields and available genotypes have varied levels of tolerance which can be exploited in the breeding programs in order to achieve a long-lasting solution to fungal diseases.