ESTIMATES OF COMBINING ABILITY FOR RESISTANCE OF WINTER RYE TO FUSARIUM-CULMORUM HEAD BLIGHT

Head blight caused by Fusarium culmorum and F. graminearum is damaging in all winter rye (Secale cereale L.) growing areas. For hybrid breed ing, the relative magnitude of general (GCA) and specific combining ab ility (SCA) is a crucial parameter for developing appropriate selectio n procedures. Forty single-cross hybrids were produced by crossing six and seven inbred lines of the Petkus and Carsten gene pool, respectiv ely, in a factorial design. Hybrids were evaluated in two years with a rtificial F. culmorum inoculation. Resistance traits were head blight rating and grain weight relative to the non-inoculated control. Both r esistance traits were closely correlated across both years (r approxim ate to-0.8, P = 0.01). Significant genotypic variation was found for b oth traits with medium to high estimates of heritability (h(2) = 0.6-0 .8). Components of variance for GCA were, across years, 10 and 6 times larger than those for SCA for head blight rating and relative grain w eight, respectively. Significant SCA effects were found for 15 to 20% of all cross combinations across both traits in each year. SCA effects were, however, inconsistent over years leading to a high SCA-year int eraction. In conclusion, resistance to Fusarium head blight among the interpool hybrids tested was conditioned mainly by additive gene actio n that could be utilized by recurrent selection in multi-environment t rials.