Occurrence of Fusarium Head Blight–causing Pathogens and Mycotoxins in Kenyan Wheat

Abstract

Fusarium head blight is a devastating disease of wheat and other small-grain cereals, causing grain yield reduction, reduced quality and mycotoxin contamination. This study was conducted in two districts of Kenya to determine the incidence of Fusarium species and mycotoxin contamination in freshly harvested wheat. A survey was carried out during the 2004 growing season in different agro-climatic zones to determine the presence of Fusarium head blight and weather conditions during the critical stages of wheat growth. Fungal contamination was determined by isolation on agar media while mycotoxin analysis was by direct competitive ELISA. Fusarium head blight was reported by 81% of the farmers and wet conditions were prevalent during anthesis. The wheat grain samples were highly contaminated with fungi, especially Epicoccum, Alternaria and Fusarium species. The mean Fusarium infection rate varied from 13 to 18%, with the major head blight – causing species being F. poae, F. graminearum, F. equiseti, and F. avenaceum. Fusarium poae, F. chlamydosporum and F. oxysporum were the most prevalent in all the agro-ecological zones while F. graminearum was isolated in 6 out of the 9 agro-ecological zones. Most grain samples were contaminated with mycotoxins deoxynivalenol, T-2 toxin, zearalenone and aflatoxin B1. The most prevalent mycotoxin was T-2 (86% of the samples) followed by deoxynivalenol (59%), zearalenone (53%), and aflatoxin B1 (52%). The maximum mycotoxin concentration was 302mg/kg, 95.8mg/kg, 65.7mg/kg and 6.9mg/kg for deoxynivalenol, zearalenone, T-2 toxin and aflatoxin B1, respectively. The incidence and levels of the mycotoxins varied depending on the agro-ecological zone. Samples with high proportion of total Fusarium infection contained higher deoxynivalenol and T-2 toxin levels. Co-occurrence of deoxynivalenol, T-2 toxin and zearalenone was fund in up to 35% of the samples. The results suggested the presence of Fusarium head blight in Kenya and associated mycotoxin contamination, though at low but significant levels. The presence of the different mycotoxins, though at low levels, could pose chronic adverse health effects to human and livestock fed on the contaminated wheat products.