INFLUENCE OF BARLEY VARIETY MIXTURES ON SEVERITY OF SCALD AND NET BLOTCH AND ON YIELD

Two susceptible barley cultivars and two moderately resistant advanced breeding lines were grown as pure stands and as the 11 possible equi- proportional mixtures over three field seasons, in the presence of sca ld and net blotch. Plots were either inoculated with infested straw, o r non-inoculated and sprayed with fungicide. On average, the variety m ixtures restricted leaf disease development by 12%. However, mixtures of either or both susceptible cultivar/s with the moderately resistant line 1861018 restricted disease severity by 20-32%. Generally, the mi xtures did not increase yield relative to the mean of the pure stands. However, in the year of highest disease severity, yield was increased by 7% owing to mixing in the inoculated plots. In addition, one mixtu re consistently increased yield (mean of 4%) and one mixture had consi stently lower yields (mean of 6%) over years and inoculation treatment s. Thus, careful evaluation is required in this environment and with t hese genotypes in order to identify mixtures with positive effects on disease control and yield.