عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Viral diseases are among the most economically important diseases of wheat in Chahar Mahal Va Bakhtiari province and cause yield losses of up to 100% in early planting fields. The following viruses were identified in the area using DAS- ELISA or TAS- ELISA: barley yellow dwarf (BYDV- PAV and BYDV- MAV), cereal yellow dwarf (CYDV- RPV), wheat dwarf (WDV), wheat streak mosaic (WSMV), maize Iranian mosaic (MIMV) and barley yellow striate mosaic (BYSMV). About 64% of symptomatic samples were infected with one or more of these viruses. BYDVs (including BYDV-PAV,BYDV-MAV and CYDV-RPV), MIMV, BYSMV and WSMV were detected in 27, 25.5, 21.5 and 20.5 percent of the samples, respectively. Most mixed infections were by BYDV serotypes with WSMV or MIMV. In milder climates MIMV was dominant, while in colder regions WSMV and BYDVs serotypes were more prevalent. Field studies were conducted in Shahrekord, Lordegan and Broujen, in seven growing seasons from 2001 through 2007, to evaluate the effect of planting date, with and without a seed- treatment insecticide (Imidacloprid),on grain yield , yield components and control of viral diseases with natural vectors in winter wheat . The experimental design was a split plot arrangement of a randomized complete block with four replications. In each of the three regions, grain yields of plots planted in the first planting date were reduced significantly by viral infection. Planting dates of 22 October and 6 November resulted in the highest grain yields and yield components in three regions. Grain yield and yield component responses to seed-treatment insecticide, depended on planting dates. In Shahrekord experiment the incidence of viral diseases was higher than other regions. Also in this region seed treatment resulted in significant yield increase of 43% to 236% depending on planting date. The plots of planting date 7 October, 22 October and 1 November with seed-treatment gave the highest grain yield and yield components and reduced viral diseases in Broujen, Shahrekord and Lordegan, respectively. During 2003-2005, 414 advanced lines and cultivars of local and commercial soft wheat were evaluated in view of their resistance level to viral diseases in agricultural research station of Shahrekord. Seeds were planted on 23 September each year under natural infection conditions. We observed symptoms of yellow dwarf disease on all lines and cultivars of wheat. According to the results, 21 advanced lines of wheat were tolerant, the other lines and cultivars of wheat being very susceptible to viral diseases. Severity of yellow dwarf disease was more than other viruses on lines of wheat.