Fusarium head blight in hard red spring wheat: Cultivar responses to natural epidemics

Fusarium head blight (FHB), caused primarily by Fusarium graminearum Schwabe, is an important but sporadic disease throughout major spring wheat (Triticum aestivum L.) production areas in Canada and the USA. Our objectives were to (i) examine the effects of gears, planting dates, cultivars, and their interactions on FHB measures and agronomic traits and (ii) characterize cultivar responses across a range of environments. Eight planting dates and 16 hard red spring wheat cultivars were studied in field trials during 1993 and 1994 at Crookston, MN. Normal and above-normal rain during June and July provided moist conditions during anthesis of most cultivars across several planting dates each year. Incidence and severity of FHB varied markedly with planting date, anthesis date, gear, and cultivar. Cultivars that achieved higher than average grain yield and test weight over all environments did so because they performed well in environments that favored FHB. Cultivar mean grain yield (r = -0.75 P = 0.01) and test weight (r = -0.93, P = 0.01) were inversely correlated with cultivar mean FHB incidence. 'Butte-86,' 'Grandin,' 'Marshall' and 'Nordic' generally had lower mean FHB incidence and severity and were less responsive to environments favorable for disease than other cultivars. These cultivars also had higher grain yield and test weight than most other cultivars. 'Norm,' 'Minnpro,' 'Sonja,' and 'Bergen' were representative of more susceptible cultivars. They had higher levels of disease, were more responsive to environments favorable for disease, and had low er grain yield and test weight. Attempts to avoid FHB by varying planting date were not successful. Careful cultivar selection for tolerance to FHB should provide moderate increases in grain yield (10-20%) and test weight (5-10%) for spring wheat producers in northwest Minnesota.