Identification of Two Major Leaf Rust Resistance Loci in the Iranian Wheat Landrace PI 621674

Leaf rust, caused by Puccinia triticina ( Pt ), is one of the most destructive wheat diseases inflicting huge economic losses globally, and identification of novel resistance sources is essential for developing resilient wheat cultivars to sustain wheat production. PI 621674 is an Iranian wheat landrace exhibiting high resistance to the representative Pt races in the USA, and identification of leaf rust resistance genes in PI 621674 is needed for its use in wheat cultivar development. A recombinant inbred line (RIL) population from the cross PI 621674 × PI 627051 was evaluated in F7 and F8 for responses to Pt race Pt54-1 (phenotyped as TNBGJ) and genotyped using single nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing. QTL analysis revealed two QTLs for leaf rust resistance that consistently expressed in both generations, designated QLr.stars-1BS and QLr.stars-5BS , in PI 621674. QLr.stars-1BS and QLr.stars-5BS were mapped in the intervals 64.67 – 66.06 Mb on chromosome arm 1BS and 9.29 – 9.71 Mb on chromosome arm 5BS in the Chinese Spring IWGSC RefSeq 2.1 reference sequence, respectively. QLr.stars-1BS explained 23.62 – 25.87% of the total phenotypic variance with LODs of 8.36 – 9.94, whereas QLr.stars-5BS accounted for 24.70 – 28.26% of the total phenotypic variance with LODs of 8.09 -10.54. QLr.stars-1BS represents a novel leaf rust resistance locus on 1BS of bread wheat, whereas QLr.stars-5BS is close to Lr52 . Two minor QTLs for leaf rust resistance were also found on chromosome arms 3AL and 6BL, respectively, in F7. KASP markers were developed for Marker-assisted selection.