GENETIC-VARIATION FOR HEAD BLIGHT RESISTANCE IN TRITICALE CAUSED BY FUSARIUM-GRAMINEARUM ISOLATES OF DIFFERENT DEOXYNIVALENOL PRODUCTION

Fusarium head blight infection causes severe yield losses and contamin ation of the grain with mycotoxins in triticale (x Triticosecale Wittm ack) grown in temperate and semihumid areas. In a two-year experiment thirty-six genotypes were inoculated separately with two isolates of F usarium graminearum differing fivefold in their in vitro deoxynivaleno l (DON) production and the effect on various traits was studied. All t raits were significantly affected by head blight. The two isolates dif fered considerably in their aggressiveness resulting in a mean reducti on of grain weight per spike of almost 25% and 50%, respectively. Inte r-annual correlation was high for average disease rating (r = 0.63, P less than or equal to 0.01) and low for the other traits. Therefore, d isease rating, averaged from two to three records, was regarded a suit able criterion for screening purposes. The effect of isolates on genot ypes was not stable over years. The mean DON content of five genotypes with diverse resistance levels was 68 mg kg(-1). In vitro DON product ion of the two isolates used for inoculation did not correspond to the ir aggressiveness and DON contamination of the grain.