Field Screening is Effective for Identifying Genetic Resistance to Scald of Barley

To evaluate barley (Hordeum vulgare L.) for resistance to scald by Rhynchosporium commune, field trials including advanced yield tests, yield and germplasm screening (YGS) trials, and race variation (RV) tests were conducted across central Alberta, Canada, from 2010 to 2014. Broad-sense heritability of scald resistance was estimated using scald severity data from these field trials. Moderate to high heritability estimates, ranging from 0.57 to 0.91, were obtained in 21 of 23 tests, each consisting of two to four sites. The heritability estimates determined were similar among the three types of field trials with the RV test having slightly higher heritability estimates. Genotype plus genotype x environment interaction (GGE) biplot analyses were used to visualize interactions between genotype and environment, and to identify scald-resistant genotypes. The scald resistance in genotypes identified based on biplots was validated by barley parentage and published data. The identified resistant genotypes are being used in an Alberta-based breeding program as sources of scald resistance. However, the reactions of some highly resistant cultivars varied with test location. Scald resistance expression depended on the virulence of local scald pathotypes and interactions with variable environmental conditions. Selection for resistance should be effective, as indicated by moderate to high heritability and field validation. Both biotic factors including R. commune pathotypes and other diseases such as the net form of net blotch (Pyrenophora teres. f. teres) and abiotic conditions affected expression of resistance. Screening over multiple years and locations is recommended along with accounting for the development of nontarget diseases.