Integrated management of wheat (Triticum aestivum L.) Fusarium head blight and deoxynivalenol contamination through host resistance and fungicide application in Ethiopia

Fusarium head blight (FHB) caused by Fusarium spp. is an emerging destructive wheat disease in Ethiopia. This disease significantly reduces grain yield and quality leading to small, shriveled, lightweight kernels and subsequently contaminating the grain with mycotoxins, particularly deoxynivalenol (DON). Field experiments were conducted in Mareko district, southern Ethiopia during the 2020 and 2021 main cropping seasons to determine the impact of integrated wheat variety resistance and fungicide application against FHB development and associated DON. Three bread wheat varieties (Denda'a, Hidase, and Kingbird), two fungicides (propiconazole and tebuconazole), and untreated wheat were used as a treatment in a split-plot design arranged in three replications. The main plots received wheat varieties, while the subplots received fungicides. The effect of fungicides on the FHB severity index was highly significant. Propiconazole and tebuconazole spraying at the anthesis growth stage reduced FHB incidence, severity, Fusarium-damaged kernels (FDK), and DON contamination in harvested grain while increasing thousand seed weight and yield in all varieties. Kingbird variety sprayed with tebuconazole had low mean FHB disease severity (19.33 and 20.20%), disease progression (0.0065 and 0.0079 units day-1), and AUDPC (316.52 and 330.17%-days) in 2020 and 2021, respectively. High mean grain yields were also obtained from a variety of Kingbird sprayed with tebuconazole. Furthermore, fungicide efficacy was found to be higher in the Kingbird variety treated with tebuconazole, with a 67% DON contamination reduction compared to the control. Unsprayed plots of each variety had the highest disease severity, DON contamination, AUDPC, and the lowest grain yield in both cropping years. The efficacy of fungicides in reducing the FHB severity index and yield increase was lower in the susceptible variety (Denda'a). Grain yield was negatively correlated to severity index, FDK, and DON, whereas the latter traits were positively correlated among themselves. The study indicated that fungicide efficacy in reducing FHB, and increasing grain yield was higher in moderately resistant varieties than in susceptible ones. The results imply that integrating fungicide application at the anthesis growth stage with moderately resistant variety is a more effective management approach for reducing FHB and DON contamination in wheat, than either approach used alone, and increasing wheat production and food security in major wheat growing areas of Ethiopia.