Infection experiments of Pyrenophora teres f. maculata on cultivated and wild barley indicate absence of host specificity

It is important to investigate the possibility of pathogen transmission between cultivated and uncultivated hosts due to the role of the latter in pathogen evolution and the creation of new pathotypes which may break resistance genes of cultivated hosts. Wild hosts can also act as a pathogen reservoir offseason and cause pathogen survival. Spot form of net blotch (SFNB), caused by the fungus Pyrenophora teres f. maculata (PTM), is an important foliar disease of barley worldwide. In this study, 19 isolates from barley and Hordeum murinum were identified as P. teres based on ITS regions and gpd sequence and 17 of these isolates were identified as the sub-species PTM based on PCR assay. In order to evaluate the pathogenicity of PTM isolates obtained from H. murinum on barley as well barley PTM isolates on H. murinum, three barley isolates and two H. murinum isolates were inoculated on one H. murinum line and four barley cultivars including Local, Jolge, Zahak and Oksin, which were previously identified as sensitive, semi-sensitive, semi-resistant and resistant to PTM, respectively. The net blotch severity was scored based on a 1-9 scale. ANOVA showed that interaction between hosts and isolates was not different significantly (Fisher's test, P = 0.05) which means that each isolate had the same pathogenic behavior on both barley and H. murinum. Therefore, it is possible to transfer pathogens from wild barley to barley as well as in the opposite direction and H. murinum can be considered a threat to barley because of its potential as a PTM reservoir between two growing seasons as well as creating new pathotypes.