Genetic and phenotypic characterisation of Yellow Rust resistance in the cultivar alcedo

Abstract

Yellow rust resistance in the German winter wheat cv. Alcedo has been described as durable, the resistance having remained effective when grown extensively in Germany and Eastern Europe between 1975 and 1989. Genetic characterisation of field resistance in a cross between Alcedo and the yellow rust susceptible UK winter wheat cv. Brigadier identified two major QTL in Alcedo located on the long arms of chromosomes 2D (QPst.jic-2D) and 4B (QPst.jic-4B). Yellow rust resistance was evaluated by measuring the extent of fungal growth, Percentage infection (Pi) and the necrotic/chlorotic response of the plant to infection, Infection Type (IT). Both QPst.jic-2D and QPst.jic-4B contributed significantly to the reduction in yellow rust infection (Pi) and were associated with a low, necrotic IT phenotypic score. In addition, two small effect QTL for field yellow rust resistance were identified in Brigadier, QPst.jic-1B on the long arm of chromosome 1B and QPst.jic-5A on the short arm of chromosome 5A. The influence of QPst.jic-1B was primarily seen with the Pi phenotype. QPst.jic-5A was only detected using an approximate multiple-QTL model and selecting markers linked to the major effect QTL, QPst.jic-2D and QPst.jic-4B as co-factors. Seedling yellow rust resistance was also mapped in the cross, which confirmed the location of Yr17 from Brigadier to the short arm of chromosome 2A. A seedling expressed QTL was also located in Alcedo that mapped to the same location as the field yellow rust resistance QPst.jic-2D.