Cytological mapping of a powdery mildew resistance locus PmRc1 by the construction of wheat-Roegneria ciliaris structural aberration library

Abstract Powdery mildew (Pm) is a fungal disease threatening wheat production. The identification of novel Pm resistance genes, especially those from wild relatives, will greatly broaden the genetic diversity of wheat breeding. Roegneria ciliaris (2n=4x=28, genome ScScYcYc) is a wheat relative. We developed 14 disomic addition lines in previous research. In this study, we identified addition line DA1Sc exhibited stable improved Pm resistance. We confirmed the Pm resistance was attributed by the added 1Sc in wheat background, and designated the locus as PmRc1. To develop translocation lines for facilitate the breeding use of PmRc1, we induced 1Sc chromosomal structural aberrations by irradiation and the Chinese Spring ph1b deletion mutant. Forty-three wheat-R. ciliaris 1Sc aberrations were identified and characterized by GISH/FISH and marker analysis using 1Sc diagnostic markers. The 1Sc cytological bin map was constructed and 1Sc was dissected into 28 bins. Pm resistance evaluation of the aberrations enabled us to allocate the PmRc1 into bin 1ScS-8, flanked by markers CMH93-2 and CMH114-1. Two compensative translocation lines (T1ScS•1BL and T1ScS-1AS•1AL), both carrying the PmRc1 and Pm resistant, were investigated for agronomic traits. T1ScS•1BL had increased grain size and weight, while decreased grain numbers. T1ScS-1AS•1AL had increased number of spikelet per spike. The translocation lines provide new genetic resource for improving Pm resistance in wheat breeding program.