Performance evaluation of some septoria leaf disease resistance genes differential wheat varieties to Ilam and Khuzestan native isolates

Wheat (Triticum aestivum L) is the main food of the people of many countries, so that it supplies more than 20% of the calories needed by the world's population, and it is cultivated in large quantities and in a large area. Bread wheat has the most trade compared to other crops.Wheat leaf septoriosis was first reported in Europe in 1842. The cause of this disease is a bipolar heterothallic ascomycete fungus, Mycosphaerella graminicola (Fuckel) J. Schrot, whose sexual cycle repeats itself during the cropping season, according to favorable environmental conditions, and since 1894, it has been observed and has been reported, although the relationship between foliar septoria and this fungus was clarified after about 80 years. This disease, which is considered one of the most destructive diseases of wheat in the world, its global damage in flood years is 30-53%.The ultimate corrective goal in any corrective program is to increase performance. This program is realized by protecting the plant against non-biotic (heat, cold, drought and salinity) and biotic (insects, bacteria, viruses and fungi) stresses, which cause a 25% reduction in yield.Breeding for resistance to foliar septuria as an environmentally friendly strategy and having an economic advantage for farmers (considering the cost of fungicide use) has gained significant importance in the last two decades.The first genetic study of wheat resistance to foliar satori disease was done in 1957 (Narvaez and Caldwell, 1957) and subsequently four resistance genes Stb1, Stb2, Stb3, Stb4 were identified and introduced in bread wheat. In the last decade, 14 new monotypes have been identified and their total number has increased to 18 in bread wheat, among which the discovery of the gene-to-gene relationship in the interaction between this fungus and wheat coincided with the identification of Stb6 (Brading et al. 2002). The comparison of the number of genes identified for resistance to foliar Seteria compared to the genes reported for other diseases seems remarkably insignificant. Therefore, increasing the number of monotypes resistant to foliar Seteria disease has become an important priority in national and international wheat breeding programs. Therefore, in this study, differential cultivars carrying genes for resistance to wheat foliar Seteria were evaluated by four isolates collected from different infected areas of Khuzestan and Ilam at the seedling stage.

In this research, 31 different varieties of wheat carrying the genes of resistance to foliar septoriosis of wheat (with Stb resistance gene) and sensitive (without Stb resistance gene) to foliar septoriosis disease, which were available in Safi Abad Dezful Research Center, were collected by 4 isolates. They were infected from different infected areas of Khuzestan and Ilam province and were evaluated in terms of disease resistance. Among the investigated cultivars, three cultivars named Taichung29, Obelisk and Darab 2 were considered as sensitive controls. The experiment was carried out as a factorial design in the form of randomized complete blocks and in three replications. The agents included mushroom isolates and differential wheat cultivars. This research was done in Dezful Agricultural Research Center. The seeds of these 31 cultivars were planted in small pots containing sand-peat soil. Necessary care was taken in terms of irrigation, light and humidity until the plants grow and reach the two-leaf stage and then contamination. During this period, watering was done every two days and between 2 and 4 cm of water was poured on the bottom of the trays.Three isolates with numbers 4, 13 and 16 were collected from several farms in Sardasht city, Dezful and Shushtar counties, and one isolate was from Ilam (5). The name and geographic location of the isolates are given in Table 2. Isolation of fungalstrains was done by single-pick method (Kema and Annon 1991) from infected leaves and each isolate was kept in a separate Petri dish containing PDA culture medium. Spores of each isolate were then propagated in a liquid culture medium with a ratio of 1:3 Ys and glucose at a temperature of 15 degrees Celsius and 180 rpm and sprayed with a concentration of 107 (10,000,000) spores per ml on the differential cultivars. In order to create favorable conditions for the penetration of fungi in the plant tissue for 48 hours, maximum humidity conditions were provided using plastic cover. 10 days after inoculation, the first leaf was preserved and the upper leaves were removed.The first symptoms of the disease were seen in the cultivar Darab 2, which was a sensitive control. The symptoms first appeared in the form of yellow spots on the leaves, which gradually spread depending on the sensitivity of the variety, and the texture of the leaves became dry and brown at the spots. Two times were considered for disease measurement and reading, one was 21 days after sporulation and the other was 28 days after sporulation. On these two dates, the disease percentage of the lines in response to the isolates was checked and recorded. The amount of disease was measured on the first leaves of the plant by measuring the percentage of pycnidium leaf surface by eye.Statistical calculations including analysis of variance and comparison of mean data were performed using LSD test and by SAS 9.2 software. It should be mentioned that before performing the analysis of variance, the assumptions of analysis of variance were tested by MINITAB 16 program and while removing outlier data, radical transformation was used to normalize the data. To draw the graphs, it was done with the help of EXCEL 2010 software.

The evaluation of the resistance level of wheat cultivars and lines to the foliar septoriosis disease in Iran has often been done using a mixture of isolates of the disease-causing fungus or under natural pollution conditions. This is not the only possibility. It does not provide a correct understanding of the level of annoyance and non-intrusiveness of Iranian separatists. Rather, it faces the problem of making an appropriate conclusion about the existence or non-existence of specific resistance in wheat numbers and lines. The results of the variance analysis tables of the response of the percentage of the peaked coverage of the numbers in relation to the wheat leaf septoriosis isolates in both experiments indicate the existence.