QUANTITATIVE RESISTANCE TO PYRENOPHORA-TERES IN 6 NORDIC SPRING BARLEY ACCESSIONS

Resistance to Pyrenophora teres Drechs. f. teres Smedeg., the net blot ch pathogen, was studied in six 6-row Nordic spring barleys (Hordeum v ulgare L.) in the field and in the greenhouse. The barley genotypes we re: Arve, Agneta, Artturi, H6221, Pohto and WW7977. Disease progress w as monitored in the field (1994 and 1995) in small artificially infect ed plots, sown at commercial seeding rates, and in infected hill plots (1994). Areas under the disease progress curves (AUDPC) and apparent infection rates (r) were calculated for the uppermost 3 or 4 leaves. T erminal severities (TS) were also recorded. Infection response of seed lings to a range of P. teres isolates was assessed in the greenhouse u sing a standard scale. In small plots in the field, Arve and Agneta we re very susceptible to P. teres infection, as indicated by large value s for AUDPC and TS. H6221 and WW7977 were highly resistant, while Artt uri and Pohto were moderately resistant. In hill plots the situation w as similar, except that Artturi and Pohto appeared less resistant than in the small plots. The relatively greater resistance of H6221 and WW 7977 was reflected in seedling infection responses. According to the r esults of these experiments, H6221 and WW7977 possess adequate levels of quantitative resistance to P teres to make them useful parents in f uture crossing programs aimed at improving net blotch resistance in Fi nnish spring barleys.