Genetic variation of head blight resistance in triticale caused by Fusarium graminearum isolates of different deoxynivalenol production

Fusarium head blight infection causes severe yield losses and contamination of the grain with mycotoxins in triticale (x Triticosecale Wittmack) grown in temperate and semihumid areas. In a two-year experiment thirty-six genotypes were inoculated separately with two isolates of Fusarium graminearum differing fivefold in their in vitro deoxynivalenol (DON) production and the effect on various traits was studied. All traits were significantly affected by head blight. The two isolates differed considerably in their aggressiveness resulting in a mean reduction of grain weight per spike of almost 25% and 50%, respectively. Inter-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, disease rating, averaged from two to three records, was regarded a suitable criterion for screening purposes. The effect of isolates on genotypes was not stable over years. The mean DON content of five genotypes with diverse resistance levels was 68 mg kg super(-1). In vitro DON production of the two isolates used for inoculation did not correspond to their aggressiveness and DON contamination of the grain.