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.