بررسی مقاومت برخی از ارقام جو نسبت به بیماری لکه نواری در شرایط گلخانه

Leaf stripe disease with the causal agent Pyrenophora graminea Ito & Kuribayashi is one of the most important barley diseases that is considered a serious threat to this crop. In order to identify the fungus that causes this disease, seed samples were collected from fields of Isfahan, Markazi, Zanjan, Tehran, Alborz, West Azerbaijan, Hamedan, Razavi Khorasan, Qazvin, Qom, Semnan, Fars and South Khorasan provinces according to the International Rules for Seed Testing (ISTA). For isolation of fungi, a number of 400 seeds of each sample were washed with water and surface sterilized with 1% sodium hypochlorite solution and were placed on different agar media, including Potato Dextrose Agar (PDA) and Potato Carrot Agar (PCA), with alternating 12 hours of light and 12 hours of darkness at 22 ± 1 °C. In total, 38 fungal isolates were obtained, which were classified based on the combination of morphological characteristics and sequences obtained from the ITS-rDNA genomic region: all isolates belonged to P. graminea. The pathogenicity tests of all the isolates isolated on susceptible Makoei cultivars were carried out under greenhouse condition at 23 ± 1 °C and a relative humidity of 70-90% with four replications. In order to assess of disease severity of isolates (as the percentage of infected leaves with leaf stripe symptoms and based on the scale 0-3), in total, five isolates of the pathogen with the highest pathogenicity were applied to Makoei (73.5%, 66.8%, 64.3%, 61.7% and 59.2%). In the continuation of this research, the experiment was conducted to evaluate the reaction of 18 different cultivars of barley, including Abidar, Ansar, Armaghan, Bahman, Behrokh, Goharan, Jolgeh, Mahoor, Mahtab, Mehr, Nik, Nimrooz, Norooz, Oksin, Qaflan, Reihan, Yosef and Zahak, to the 20 selected isolate representatives using the sandwich method. Seeds sterilized by 1% sodium hypochlorite solution, placed in two fungal layers, have grown on a PDA culture medium for contamination. Sandwiches containing isolates and seeds were kept at a temperature of 12-14 °C and in dark conditions for 14-21 days. There was a significant difference between the investigated cultivars in terms of resistance to different isolates of the disease causing fungus. The results showed that Oksin, Nimrooz and Norooz cultivars with lower pathogenicity than other cultivars were identified as resistant cultivars. Armaghan, Ansar, Goharan, Behrokh, Nik, Bahman, Jolgeh, Mahoor, Mehr, Qaflan, Zahak and Yosef cultivars as semi-resistant cultivars, and also Abidar, Reihan and Mahtab cultivars had the highest level of symptoms and infection as sensitive cultivars. From the results of this research, it is possible to carry out corrective research in order to identify and correct the cultivars resistant to leaf stripe disease.