Marker assisted selection to pyramid seedling resistance gene Lr24 and adult plant resistance gene Lr48 for leaf rust resistance in wheat

Abstract

One Agropyron elongatum derived dominant seedling resistance gene (Lr24) and one recessive adult plant resistance (APR) gene (Lr48) for leaf rust resistance, were pyramided together employing marker assisted selection (MAS) with sequence characterized amplified region (SCAR) marker SCS1302607 tagged to the gene Lr24 and two random amplified polymorphic DNA (RAPD) markers flanking the gene Lr48, S3450 and S336775 in wheat. The RAPD marker S3450, linked in repulsion phase amplified a 450 bp marker fragment corresponding to the recessive resistance allele and the other marker S336775 linked in coupling phase amplified a 775 bp marker fragment corresponding to the dominant susceptibility allele of the Lr48 locus. Parental genotypes comprised of the near isogenic line (NIL) of the most widely grown cultivar PBW343 possessing Lr24 and an Australian cultivar CSP44 possessing APR gene Lr48. Phenotyping was done after inoculating with pathotype 77-5 of Puccinia triticina and integrated with MAS under controlled conditions of Phytotron (for F1 and F3 generations) and natural field conditions (for selection in F2 and F4 generations). Agronomic suitability of the marker positive plants was integrated for generating the F3 families and selecting the F4 subfamilies. MAS facilitated the identification of 26 F4 subfamilies fixed for both the genes with desirable plant type from three F3 families homozygous for dominant gene Lr24 selected from 38 F2 single plants homozygous for APR Lr48. The selected F4 subfamilies were furthered for seed bulking and yield performance in F5 generation.