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

Population genetic structure of four regional populations of the barley pathogen Pyrenophora teres f. maculata in Iran is characterized by high genetic diversity and sexual recombination

The leaf spot form of the barley disease net blotch, caused by the fungus Pyrenophora teres f. maculata (PTM), is an increasingly important foliar disease of barley. Studies of population genetic structure and reproductive mode are necessary to make predictions of the evolutionary potential of the pathogen. Sources of resistance to PTM have been found in Iranian landraces, which may have the potential to improve plant breeding efforts. However, little is known about the population genetic structure of this fungus in Iran. In this study, we analysed the frequency of the mating type genes to assess the potential for sexual mating of PTM collected from four provinces-Khuzestan, Hamadan, Golestan, and East Azerbaijan-and we investigated the population genetic structure using seven simple sequence repeat markers. High genotype diversity, linkage equilibrium, and equal ratios of mating types frequencies in the PTM populations at Khuzestan and Hamadan support the occurrence of sexual reproduction in these populations, while in Golestan and East Azerbaijan populations, significant gametic disequilibrium and relatively low genotype diversity suggest a higher incidence of clonality or different demographic histories. Unequal mating type frequencies in Golestan confirm a predominance of asexual reproduction. Finally, we found significant evidence for strong population structure with most of the genetic variation represented within regional populations (89%). Overall, our study provides evidence for high genetic variation in Iranian PTM populations, which may be the basis for rapid adaptive evolution in this pathosystem. This highlights the need for integrated efforts to control the disease