Symptomatology and Identification of Major Fungal Pathogens of Pyrethrum (Chrysanthemum cinareriifolium) in Kenya

Abstract

Fungal pathogens are major biotic constraints in almost all pyrethrum producing zones in the world. Due to limited information, this study was designed to document on symptomatology and diversity of major fungal pathogens of pyrethrum in Kenya. Stratified random sampling technique was applied during a field sampling in major production zones of Nakuru County where agro ecological zones were considered as strata and on each stratum, biased sampling was used to sample pyrethrum tissues showing symptoms of fungal infections. Disease symptoms on these samples were described based on the findings of earlier scholars. The samples were taken to University of Eldoret Plant Pathology Laboratory for fungal isolation, morphological studies and identification. Surface sterilized samples were cultured on PDA media and incubated at 25 ^oC - 27 ^oC for seven days after which the actively growing fungal mycelia were sub cultured to obtain pure isolates on a freshly prepared PDA and incubated at alternating 12 hours of light and darkness to induce sporulation. A light microscope was used at X1000 magnification to assess micro characteristics while Color charts were used to describe macro characteristics of isolates and laboratory manuals, journals and reference books were used to confirm the actual identities of each isolate. Frequency of occurrence was assessed based on sites as well. Three major diseases were described in both sites; Bud disease, crown rot disease and pyrethrum wilt disease. A total of ten diverse pure isolates belonging to six different genera were obtained from the samples analyzed and from these isolates, genus Fusarium was the most abundant with four different species namely F. oxysporum, F. solani, F. graminearium and F. avenaceum. Followed closely by the genus Alternaria with three species isolated and they include Alternaria solani, Alternaria alternata and Alternaria tenuissima. Other identified fungi were Rhizoctonia solani, Phoma spp and Sclerotinia minor. It is evident that a wide range of fungal pathogens are responsible for low pyrethrum yield and pyrethrum quality in Kenya thus the need to exploit effective management strategies.

Keywords: Symptomatology, identification, fungi, pyrethrum

DOI: 10.7176/JBAH/14-1-09

Publication date: June 30^th 2024