Genomic regions conferring resistance to rust diseases of wheat in a W195/BTSS mapping population

Global wheat production is constrained by rust diseases and deployment of combinations of genetically diverse sources of resistance in new cultivars is accepted as a preferred means of rust control. This investigation was planned to identify new genomic regions contributing towards resistance to three rust diseases under field conditions in a W195/BT-Schomburgk Selection (BTSS) RIL population. The RIL population was assessed for variation in stripe rust, leaf rust and stem rust responses at two locations during 2012 and 2013 crop seasons and was subjected to DArTseq genotyping. Linkage map was constructed using 3439 DArTseq markers with an average marker density of 2.7 cM. Composite interval mapping detected three QTL each for stripe rust, leaf rust and stem rust resistance in W195/BTSS RIL population. Two consistent QTL for stripe rust, QYr.sun-3BS and QYr.sun-4DL, were contributed by W195 and one inconsistent QTL, QYr.sun-7AS, by BTSS. In the case of leaf rust QLr.sun-2BS and QLr.sun-3BS were contributed by BTSS and QLr.sun-4DL by W195. Based on seedling tests, QLr.sun-2BS was demonstrated to be Lr23. BTSS carried stem rust QTL; QSr.sun-2BL and QSr.sun-6AS and QSr.sun-4DL was contributed by W195. QSr.sun-6AS corresponded to stem rust resistance gene Sr8a carried by BTSS. The collocated QTL for all three rust diseases in chromosome 4D corresponded to the plieotropic locus Lr67/Yr46/Sr55/Pm46 based on genotyping with a linked SNP marker. Interaction among QTL to condition lower rust responses was also demonstrated. QYr.sun-3BS, QLr.sun-3BS and QSr.sun-2BL represent new rust resistance loci.