GRAIN-YIELD, NET BLOTCH AND SCALD OF BARLEY IN FINNISH OFFICIAL VARIETY TRIALS

Data on grain yield, and terminal severity of net blotch (Pyrenophora teres f. teres) and scald (Rhynchosporium secalis) from Finnish offici al barley (Hordeum vulgare) variety trials were analysed to indicate t he pattern of disease incidence over six years and five sites for nine teen barley genotypes, and the effect of the diseases on yield and the genotype by environment interaction for yield. The effect of climatic factors on net blotch severity were also investigated. The genotype b y site interaction for net blotch severity was not statistically signi ficant, but that for yield was. Net blotch severity differed between y ears, but was similar across sites and there were statistically signif icant first order interactions between year, site and genotype. 'Saana ' and 'Thule' had relatively low mean terminal net blotch scores and t heir reaction to the disease was less sensitive to the environment tha n was that of 'Tyra' for example. Analysis of yield data adjusted for net blotch severity indicated that the magnitude of the genotype by en vironment interaction terms were not accounted for to any significant degree by differences in relative net blotch resistances among the bar ley genotypes. Overall, mean scores for scald severity were lower than those for net blotch. Terminal net blotch severity was correlated wit h May rainfall and growing degree days.