VARIATION IN SUSCEPTIBILITY OF WHEAT PARTS TO MAJOR Fusarium HEAD BLIGHT PATHOGENS
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Abstract

Fusarium head blight (FHB) of wheat is caused by a complex of pathogens with F. graminearum, F. culmorum, F. poae, F. avenaceum and F. tricinctum being the most common worldwide. Besides ears, the species have been isolated from wheat roots, foot, stems, ears and leaves. Greenhouse studies were carried out to investigate differences in susceptibility of wheat parts – leaves, stems, kernels and spikelets – to the five Fusarium species inoculated at midanthesis. Tissue susceptibility was assessed by establishing Fusarium spp. re-isolation frequency 20 days post inoculation. Additionally, FHB severity and effect of the disease on grain weight were assessed. Tissue susceptibility to the Fusarium isolates varied significantly (p ≤ 0.05) and was in decreasing order: spikelets (mean 83%), kernels (mean 79%), stems (mean 75%), and leaves (mean 31%). Fusarium graminearum and F. culmorum were re-isolated in the highest frequency from spikelets and kernels, respectively while the corresponding lowest re-isolation frequencies were F. avenaceum and F. poae; and F. poae. Fusarium head blight was initiated earlier and progressed significantly faster (p ≤ 0.05) on plants inoculated with F. culmorum and F. graminearum than the other three isolates. Area under disease progress curve varied significantly (p ≤ 0.05) and decreased in the order: F. graminearum, F. culmorum, F. tricinctumF. avenaceum and F. poae, respectively. All Fusarium isolates except F. poae caused a significant reduction in 1000-kernel weight with F. culmorum resulting in the highest (87%) reduction, compared to non-inoculated controls. Fusarium species infect vegetative wheat parts where they may survive between cropping cycles and contribute inoculum for FHB development in a subsequent crop.