Mapping of QTL conferring resistance to sharp eyespot (Rhizoctonia cerealis) in bread wheat at the adult plant growth stage

Abstract

Seven sharp eyespot resistance QTL were detected consistently across five environments and delimited to seven DNA marker intervals, respectively, six of which were independent of plant height and heading time. Sharp eyespot, caused mainly by the soil-borne fungus Rhizoctonia cerealis, is one of the important diseases of bread wheat (Triticum aestivum L.). This disease has escalated into a major threat to wheat production in some regions of the world. Wheat resistance to sharp eyespot can be a potential means to reduce the needs for application of fungicides and agricultural inputs. In the present study, the winter wheat lines, Luke and AQ24788-83, both of which possess quantitative resistance to sharp eyespot, were crossed and a population consisting 241 recombinant-inbred lines (RILs) was constructed. These RILs were assessed for sharp eyespot resistance by conducting five field and greenhouse trials during the period from 2008 to 2012, and they were genotyped with 549 simple-sequence repeat DNA markers. Seven quantitative trait loci (QTL) were detected consistently across the five trial environments to be associated with the sharp eyespot resistance. They were mapped on chromosomes 1A, 2B, 3B, 4A, 5D, 6B, and 7B. Four of these QTL are unequivocally novel, while it is possible that the other three might also be novel. Plant height and heading date of the 241 RILs were recorded in the four field trials. All of the seven disease resistance QTL were independent of plant height and heading time except one that was significantly associated with plant heading time. This association might be attributed genetically to a single QTL, or to different but closely linked QTL. In the case of single QTL, pleiotropism might be involved or the sharp eyespot resistance might be conferred in a physical instead of physiological nature.