Effect of nitrogen fertilization on seed-borne Fusarium species in oat

Fusarium head blight is a common disease of oat and resistant cultivars are not available in Canada. The effect of nitrogen (N) fertilization on the incidence of seed-borne Fusarium spp. was evaluated under natural field conditions in three locations (Ottawa, ON; Melfort, SK; and Normandin, QC) in Canada in 2013 and 2014. At each site, oat cultivars CDC Morrison, AAC Nicolas, and AAC Noranda were used under four levels of N fertilization (0, 50,100, and 150 kg N ha(-1) ). Of the seven Fusarium spp. recovered, F. poae, F. equiseti, F. graminearum, F. sporotrichioides, and F. avenaceum were the most common species and were isolated from 9.6%, 1.3%, 1.1%, 1.0%, and 0.3% of the harvested grain, representing 72%, 10%, 8%, 7%, and 3% of the pathogen population, respectively. The remaining species, F. acuminatum and F. oxysporum, were each recovered from a single seed only. A significant N treatment effect (P < 0.05) was observed in four of the six location-years in which the highest N treatment of 150 kg N ha(-1) resulted in greater incidence of the predominant species (F. poae) and total Fusarium spp. than the untreated control (0 kg N ha(-1) ). Among the commonly recovered species, only seed-borne infection by F. graminearum increased significantly with the levels of N treatments applied. A highly significant effect of location, year, and location x year interaction (P < 0.01) was observed, suggesting that the field and weather conditions have a stronger influence on incidence of seed-borne Fusarium spp. than the N treatments.