Impact of pathogenic Fusarium species on sorghum in Uruguay

Abstract

Sorghum is the third major rainfed summer crop after maize and soybean in Uruguay. Worldwide this crop is affected by Fusarium spp. that infect and colonize panicles, kernels, peduncles, stalks, and roots, causing yield losses and threatening grain quality. In Uruguay, F. graminearum sensu stricto (F. graminearum s.s.) is the predominant species in grain, followed by F. proliferatum, F. andiyazi, F. fujikuroi, and F. thapsinum, but little is known about these species in the country. To assess pathogenicity, a mixture of three Fusarium isolates from each of the five species were used to inoculate sorghum peduncles and stalks for two years in the greenhouse. Fusarium spp. produced lesions with necrosis surrounded by reddening of the pith tissues on the inside of the lengthwise cut peduncles and stalks. All five species were equally aggressive on peduncle when the disease was conducive, while only F. graminearum s.s. affected stalks. Yield and thousand kernel weight were affected by F. graminearum s.s. and F. fujikuroi in both peduncle and stalk inoculations, when severity was high.