Seed Borne Fungal and Bacteria Pathogens Associated with Farmer-Stored Sorghum Seeds from Eastern, Coast and Nyanza Regions in Kenya

Abstract

Sorghum (Sorghum bicolor (L.) Moench) is an important cereal crop in Kenya. Access to good quality seeds is one of the constraints facing the small scale farmers in key areas growing sorghum. Good quality seed is an important factor for maintaining plant population and increasing crop yield to attain food security. One of the important aspects of good seed, besides high germination and purity is the absence of seed borne pathogens. In the present study, an experiment was carried out to identify fungal and bacterial pathogens associated with farmerstored seeds of sorghum. The seeds were collected from farmers in Nyanza, Coast and Eastern regions, Kenya. The seeds were washed with sterile distilled water and sterilized in 1% Sodium hypochloride for 5 minutes, rinsed with sterile distilled water and dried using a blotting paper. The dried seeds were placed onto prepared Potato Dextrose Agar (PDA) and macerated seeds streaked on nutrient Agar (NA) on sterile Petri dishes and incubated at 23±2 0 C. The growing pathogens were sub-cultured on new media to make pure cultures. A segment of mycelia from the sporulating colonies in each pure culture was examined under a compound microscope and identified based on their morphology, colour and mycelia growth characteristics for fungi while bacterial identification was done using colony color and morphology on nutrient agar and biochemical tests. Ten fungal pathogens and one bacterium were identified growing on the sorghum seed samples. These were Acremonium spp., Alternaria spp., Aspergilus niger, Bipolaris cookie, Collectotrichum graminicola, Fusarium moniliforme, Fusarium solani, Fusarium ventrichosum, Phythium aphanidermatum, Rhizoctonia spp. and a bacterium Xanthomonas spp. It was observed that majority (32%) of the seed samples from Coast region were infected with bacteria Xanthomonas spp. Phythium. aphanidermatum was the most prevalent fungal pathogen detected on seed samples from Nyanza region with about 20% prevalence. Results showed that majority of the seed samples from all the regions were contaminated with various pathogens. This study highlights the need to create awareness to farmers on the use of proper production practices, storage facilities and conditions to improve the quality of stored sorghum seeds.