Mapping of Lr56 translocation recombinants in wheat

Abstract

In an attempt to transfer the Lr56/Yr38 resistance loci from Aegilops sharonensis to wheat, a 6A‐6Ssh chromosome translocation was produced. It involves essentially the entire chromosome 6Ssh with a small terminal segment of 6AL. Induced homoeologous recombination of the translocated chromosome with 6A produced numerous recombinants including three recombined chromosomes carrying Lr56 that could not be precisely mapped for lack of suitable markers. This study aimed to determine the chromosomal locations of the translocation breakpoints in these three recombinants using various DNA markers as well as physical and genetic mapping. The three recombinants Lr56‐39, ‐157 and ‐175 carry small segments of Ae. sharonensis chromatin distally to the Xgpw4329 and IWA5416 loci near the 6AS telomere. The Ae. sharonensis chromatin that remains in each line includes a homoeolocus of the wheat marker locus Xdupw217 (on 6BS) and its characteristic amplification product can be used as a dominant marker for the presence of Lr56. Of the three recombined chromosomes, Lr56‐157 retained the least alien chromatin and appears to be the best candidate for use in wheat breeding.

Engineered Versions of the Wheat Lr62 Translocation

“…Substantially shortened versions of the Lr59 (Pirseyedi et al, 2015), Lr56 (Somo et al, 2016), and Lr62 (current study) translocations have been identified. Another 6BS translocation ( Lr53 from Triticum dicoccoides ) has been described by Marais et al (2005).…”

“…In addition, the introgressed regions always included an alien homoeo‐locus of the Xdupw217 marker locus (Table 2), and, in the case of translocations involving the 6BS chromosome arm, it had replaced the corresponding wheat locus. Marker information pertaining to the Lr56 ‐157 (Somo et al, 2016) and Lr62 ‐135 translocations on 6AS are compared in Table 3, which shows their similar locations. These findings suggest that Lr62 ‐135 is a comparatively large translocation.…”

Identification of novel leaf rust seedling resistance loci in Iranian bread wheat germplasm using genome-wide association mapping

“…Three catalogued Lr genes, Lr56, Lr62 (Marais et al 2008), and Lr64 (Kolmer et al 2010), and two QTLs, IWA680_6AS and 6A_t1 (Gao et al 2016; Turner et al, 2016) have already been detected on chromosome 6A for leaf rust resistance. Lr56, Lr62 , and Lr64 are seedling resistance genes originated from Aegilops sharonensis, Aegilops neglecta and, Triticum dicoccoides , respectively (Somo et al 2016; Kolmer et al 2010). Due to the lack of genetic materials that carries these genes in our GWAS panel, it is unlikely that this locus represents Lr56, Lr62 , and Lr64.…”

Registration of Spring Wheat Sources of Leaf Rust Resistance Genes Lr53, Lr56, Lr59, and Lr62

“…In the case of recombinant Lr62 ‐129, Xdupw217 negl (251 bp) had replaced the common wheat Xdupw217 aest locus on 6BS and thus can also be used as a codominant marker. In 15 wheat genotypes that have been studied so far (Somo et al, 2016), the Xdupw217 aest allele was smaller than in the alien translocations and associated with amplification products of sizes null, 230, 240, and 242 bp; however, this may not be true for all wheat genotypes.…”

“…sharonensis chromatin (and lacked Yr38 ) were identified. Continued physical and genetic mapping in association with genomic in situ hybridization (GISH) showed that Lr56 ‐157 is the shortest of the three recombined translocations and that it occurs within the 6AS telomeric region (Somo et al, 2016).…”