ASSESSING NONSPECIFICITY OF RESISTANCE IN WHEAT TO HEAD BLIGHT CAUSEDBY INOCULATION WITH EUROPEAN STRAINS OF FUSARIUM-CULMORUM, F-GRAMINEARUM AND F-NIVALE USING A MULTIPLICATIVE MODEL FOR INTERACTION

To determine whether resistance to Fusarium head blight in winter whea t is horizontal and non-species specific, 25 genotypes from five Europ ean countries were tested at six locations across Europe in the years 1990, 1991, and 1992. The five genotypes from each country had to cove r the range from resistant to susceptible. The locations involved were Wageningen, Vienna, Rennes, Hohenheim, Oberer Lindenhof, and Szeged. In total, 17 local strains of Fusarium culmorum, F. graminearum, and F . nivale were used for experimental inoculation. One strain, F. culmor um IPO 39-01, was used at all locations. Best linear unbiased predicti ons (BLUPs) for the head blight ratings of the genotypes were formed w ithin each particular location for each combination of year and strain . The BLUPs over all locations were collected in a genotype-by-environ ment table in which the genotypic dimension consisted of the 25 genoty pes, while the environmental dimension was made up of 59 year-by-strai n-by-location combinations. A multiplicative model was fitted to the g enotype-by-environment interaction in this table. The inverses of the variances of the genotype-by-environment BLUPs were used as weights. I nteractions between genotypes and environments were written as sums of products between genotypic scores and environmental scores. After cor rection for year-by-location influence very little variation in enviro nmental scores could be ascribed to differences between strains. This provided the basis for the conclusion that the resistance to Fusarium head blight in winter wheat was of the horizontal and non-species spec ific type. There was no indication for any geographical pattern in vir ulence genes. Any reasonable aggressive strain, a F. culmorum strain f or the cool climates and a F. graminearum strain for the warmer humid areas, should be satisfactory for screening purposes.