پایش بیماری زنگ زرد در مرحله گیاه کامل در خزانه بین‌المللی گندم نان در منطقه گرگان

Variation and selection play a key role in breeding programs and the proper selection is related to the desired variation in the desired trait. It seems to take advantage of the existing variation; the evaluation of germplasm resources is necessary. Yellow rust disease (Puccinia striiformis f. sp. tritici) is the most important wheat disease in Iran that is observed in most parts of the country. The warm and humid agro-climatic zone of northern Iran is prone to the emergence of this disease due to high relative humidity. The use of resistant cultivars is the most economical way to reduce the application of chemical fungicides. In order to select the top lines of 16STEMRRSN nursery (Stem Rust Resistance Screening Nursery); received from the International Maize and Wheat Improvement Center (CIMMYT), 135 spring bread wheat genotypes were evaluated as observational approach at Gorgan Agricultural Research Station in the 2021-2022 cropping season. To further spread the yellow rust infection, Falat cultivar (susceptible) was cultivated in the margin of the trail. Taktaz cultivar was also used as a resistant control. After the complete establishment of the disease on the susceptible cultivar in the adult plant stage, taking notes in the stage of flag leaf emergence were recorded based on the infection type, as susceptible (S), moderately susceptible (MS), resistant (R), moderately resistant (MR) and immune (O). Infection severity was also graded from 0-100. The coefficient of infection (CI) was calculated by multiplying the disease severity in the constant values that is related to the plant response (O = 0, R = 0.2, MR = 0.4, MS = 0.8 and S = 1). Due to the favorable climatic conditions for the pathogen, in March and April, yellow rust disease was well established and spread. The results showed that based on the infection type, 16 lines (12%) were moderately resistant and 21 lines (16%) were moderately susceptible and 61 lines (45%) were susceptible to yellow rust. Also, no signs of infection were observed in 37 lines (27%). Based on the coefficient of infection (CI), 30 lines (22%) were resistant, 26 lines (19%) were moderately resistant, 19 lines (14%) were moderately resistant to moderately susceptible and 23 lines (17%) were moderately susceptible. Of the top 10 lines in terms of grain yield, four, three and three lines were immune, resistant and moderately resistant to yellow rust disease, respectively.