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Leaf stripe, caused by the fungus Pyrenophora gramineaIto et Kuribayashi [anamorph Drechslera graminea(Rabenh. ex. Schlech.) Shoemaker], is an important seed‐borne disease of barley (Hordeum vulgareL.). The objective of this study was to verify the reliability of a PCR‐based marker (MWG2018) associated with the resistance gene Rdg2aand to assess the leaf stripe resistant phenotype in barley breeding programs. A large number of barley cultivars and accessions were thus evaluated for their reaction to a highly virulent monoconidial isolate (Dg2) of the pathogen and genotyped for the allele of the molecular marker. Several resistant genotypes were identified and four were shown to possess the same allele as the cultivar Thibaut (the resistant parent of the original mapping population in which Rdg2awas identified) at the marker locus. One of them, cv. Rebelle, is being used as a source of leaf stripe resistance in winter barley breeding programs. The allelic composition at the MWG2018 locus was verified in several resistant lines bred from five crosses, in which Rebelle acted directly or indirectly as donor of the resistance. The results showed that the resistant phenotype of the lines was always associated with the resistance allele of the molecular marker, thereby demonstrating its reliability for selecting leaf stripe resistance. The MWG2018 PCR‐based marker can therefore be proposed as a tool to assess the resistant phenotype.

In agricultural systems, monocrop has become a common practice. Barley responds quite well to continued cultivation, however reduction in the yield can become significative. We show that, for barley grown in the Po Valley, yield reductions are associated to increasing infections by soil-borne viruses, BaYMV and BaMMV. Over the three years of trials, only the cultivars susceptible to such viruses showed high incidence of the viruses and relevant grain yield losses (33%), while the resistant ones had no virus infection and no yield reductions. Increased nitrogen dressing, although could reduce the incidence of viruses at the stage of initial stem elongation, did not allow a recovery of yield loss. Mosaic viruses are transmitted by fungus Polymyxa graminisand the repeated growth of susceptible barley cultivars can increase the incidence of the infection in the subsequent barley crop.