Genotypic and environmental variation of resistance to head blight in triticale inoculated with Fusarium culmorum

Fusarium head blight (FHB) is a widespread disease of small-grain cereals a nd can cause substantial losses in grain yield. To assess quantitative gene tic parameters as a basis for an efficient breeding programme for resistanc e, 100 triticale (x Triticosecale Wittm.) genotypes were tested in various environments and artificially inoculated at anthesis with an aggressive iso late of fusarium culmorum. A visual rating (1-9 scale) was used to assess h ead blight infection. Five grain yield traits relative to an uninoculated c ontrol were also measured. The mean value of the average rating, calculated from our or five readings, was 4.4. It ranged from 3.0 to 5.9 and showed c ontinuous variation. Infection caused a 48% reduction of mean kernel weight per spike, which was the result of 26% fewer kernels per spike and a 32% l ower 1000-kernel weight. The 50-ml kernel weight was affected by only 20%. The range and genotypic variation was highest for relative kernel weight pe r spike. For all relative grain yield traits, the most important source of variation was the environment, followed by genotype-environment interaction , with genotype generally coming last. In contrast, genotypic variation was the most important factor for the disease rating, which also had the highe st heritability (h(2) = 0.89). Phenotypic correlations between the average head blight rating and relative grain yield traits were moderate (r = 0.42- 0.57). In conclusion, an average disease rating provides a quantitative ass essment of resistance and is suitable for screening large numbers of genoty pes. Relative kernel weight per spike gives a ranking of the genotypes that is very similar to the visual score.