Field-based assessment of partial resistance to yellow rust in some candidate wheat lines

Wheat yellow rust, caused by Puccinia striiformis f. sp. titici , is one of the most important and most destructive diseases of wheat in many parts of Iran, which decreases crop yield in epidemic years. Host resistance is the most economical method for the management of yellow rust and partial resistance (a type of quantitative resistance), proven to be more durable than other types of resistances. In this study, partial resistance parameters including coefficient of infection (CI), final disease severity (FDS), relative area under disease progress curve (rAUDPC) and apparent infection rate (r) were evaluated in a set of twenty-four wheat genotypes along with susceptible control during two crop years from 2015 to 2016. The research was conducted at Allarough Agricultural Research Station in Ardabil, under natural and artificial inoculation conditions. Artificial infection of genotypes was performed using the yellow rust race population having virulence for Yr2, Yr6, Yr7, Yr9, Yr17, Yr22, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, Yr26, Yr27, Yr21, Yr21, Yr31, Yr32 and YrSU resistance genes. Seedling response was also evaluated under field conditions. The evaluation of resistance parameters showed that six lines were resistant at both seedling and adult plant stages. Eleven lines showed resistance reaction at seedling stage, but moderate or susceptible reactions at adult plant stage. Seven lines (entries; 1, 4, 7, 8, 9, 16, 22) were susceptible at the seedling and had moderate (MR, M or MS) reactions at adult plant stages. Therefore, these lines having low values ​​of different resistance parameters are likely to have varying degrees of partial resistance or high temperature adult plant resistance (a type of non-specific or durable resistance). Cluster analysis based on the reaction of seedling and adult plant, divided the lines into different groups, which also indicated a high diversity of lines in response to yellow rust disease.