Evaluation of virulence of Pyrenophora gramina isolates collected from barley fields of Azarbaijan region

In order to study the virulence of Pyrenophora graminea isolates from 19 barley fields of Azarbaijan Provinces, a research program was conducted in the Plant Protection Department, Faculty of Agriculture, University of Tabriz, Iran, in 2000, using the susceptible variety of Zarjo.After isolation, 26 isolates were purified via hyphal-tip culture. The Sandwich method was used to inoculate the seeds. Isolates were rated according to the method of Mathur and Bhatangar.Results showed that 8 isolates Marand 3, Bostonabad, Khasseban-Tirre, Ajabshir 2, Ahar 2, Osku 1 Ghahveie, Marand 2/1 and Azarshahr with more than 50% (50-100%) infected plants were very virulent, 7 isolates Khoy, Osku 2- Sefeed, Mianeh 1, Marand 2/2 and Ajabshir 1 with 25-50% infected plants were virulent, the others were classified as intermediate, weak and very weak. Since many isolates were highly virulent and could cause substantial yield loss in each growing season, it is necessary to conduct studies to evaluate barley varieties and landraces in order to select genotypes resistant to leaf stripe of barley.