Partial resistance of barley to leaf rust, Puccinia hordei. II. Relationship between field trials, micro plot tests and latent period

Summary

Of 16 barley cultivars the partial resistance to leaf rust, Puccinia hordei, was measured in field plots isolated from each other by at least 30m of winter wheat. The partial resistance caused by a lower infection frequency, a longer latent period, a lower sporulation rate or a shorter sporulation period, or a combination of these, varied greatly among the cultivars, of which 9 were tested in 1973 and all 16 in 1974. The correlation with the assessments obtained from small, adjacent plots, where the epidemic is determined by the spreader rows and the susceptible cultivars, was very high (r=0.95 to 0.96), The correlation with latent period in the seedling stage was moderate (r=0.57), with latent period in the young flag leaves very high (r=0.92). The assessments obtained from the small, adjacent plots, although evaluating the partial resistance of the cultivars in the right order did under estimate the partial resistance very strongly. As cultivar testing for variety-lists is generally done in this way, though the plots may be larger, the values for partial resistance entered into such variety-lists may often under estimate the resistance seriously.