| 0 | PI 682091 | Thatcher-Lr53 | Triticum aestivum L. subsp. aestivum | North Dakota, United States | NSGC |  | | 2017 | DEVELOPED | | | | | | Breeding material | Leaf rust (caused by Puccinia triticina Erikss.) resistance gene Lr53 was found in Triticum turgidum L. ssp. dicoccoides (2n=4x=28=AABB) and then transferred through backcrosses to common wheat cultivar Chinese Spring (CS), resulting in the near-isogenic line (NIL), CS-Lr53 with pedigree: T. dicoccoides/ 4*CS// 2*CS-S/3/ CS. Lr53 was subsequently mapped to chromosome arm 6BS. The gene was also introduced through four backcrosses into the genetic background of the spring wheat cultivar Thatcher to produce the Thatcher-Lr53 NIL. Lr53 is closely associated with an alien homoeo-allele of the wheat simple sequence repeat marker locus Xdupw217 that occurs at the 6BS telomere. In seedling tests, Lr53 provided promising resistance to a broad range of races in South Africa and North America; however, it has not been widely employed in breeding. Based on its broad major gene resistance, its similar location at a group 6 chromosome short arm telomere, and close proximity to the Xdupw217 marker locus, Lr53 could be a homoeo-locus of Lr56, Lr59, and Lr62. [See PI 682091 - 682094 for accessions from the same JPR publication.] | 1949927 | PI 682091 |
| 1 | PI 682092 | Lr56-157 | Triticum aestivum L. subsp. aestivum | North Dakota, United States | NSGC |  | | 2017 | DEVELOPED | | | | | | Breeding material | Leaf rust (causal fungus= Puccinia triticina Erikss.) resistance gene Lr56 derives from Aegilops sharonensis (Hackel) Maire et Weiler (genomes SshSsh), a diploid wild relative of common wheat. A large original translocation to wheat chromosome 6A was obtained which was then shortened through induced recombination in the absence of Ph1. Fifty three recombinants were recovered that retained Lr56 in conjunction with reduced amounts of Ae. sharonensis chromatin. Physical and genetic mapping showed that Lr56-157 is the shortest, potentially most useful translocation recombinant and that it occurs within the 6AS telomeric region. The Ae. sharonensis chromatin that remained on chromosome arm 6AS in recombinant Lr56-157 includes a characteristic Xdupw217 homoeo-locus (allele size= 251 bp) that can be used as a dominant marker for the presence of Lr56. Lr56 exhibited broad effectiveness in seedling resistance tests involving North American and South African pathotypes of P. triticina, yet has not been widely employed in breeding due to the large size of the original translocation. Based on its broad major gene resistance, its similar location at a group 6 chromosome short arm telomere, and close proximity to the Xdupw217 marker locus, Lr56 could be a homoeo-locus of Lr53, Lr59, and Lr62. [See PI 682091 - 682094 for accessions from the same JPR publication.] | 1949928 | PI 682092 |
| 2 | PI 682093 | Lr59-151 | Triticum aestivum L. subsp. aestivum | North Dakota, United States | NSGC |  | Not Available | 2017 | DEVELOPED | | | | | | Breeding material | Leaf rust (caused by Puccinia triticina Erikss.) resistance gene Lr59 was transferred from Aegilops peregrina (Hackel) Maire et Weiler (2n=4x=28=UUSS) to common wheat chromosome arm 1AL in an apparent Robertsonian translocation event. Homoeologous pairing induction between this original translocation and 1AL was then employed to genetically map Lr59 and to identify the most useful recombinants. Eight of 160 recombinants that proved to have the least alien chromatin were studied more intensively. It became apparent that the distal end of the original translocation was structurally different from 1AL as it had group 6 chromosome homoeology and a 6BS telomere which facilitated a low frequency of multivalent formation during allosyndetic pairing. Crossover within multivalent structures resulted in the comparatively smallest translocations. Seven of the eight smallest translocation recombinants were compensating, interstitial Ae. peregrina chromatin inserts within the 6BS satellite region. Simple sequence repeat marker results showed that Lr59-151 was the shortest of these. In recombinant Lr59-151 the translocation has also replaced the wheat 6BS Xdupw217 marker locus with a unique Ae. peregrina homoeo-locus (253 bp allele). Lr59 provides promising, broad spectrum resistance, yet has not been used in breeding. Based on its broad major gene resistance, its similar location at a group 6 chromosome short arm telomere, and close proximity to the Xdupw217 marker locus, Lr59 could be a homoeo-locus of Lr53, Lr56, and Lr62. [See PI 682091 - 682094 for accessions from the same JPR publication.] | 1949929 | PI 682093 |
| 3 | PI 682094 | Lr62-129 | Triticum aestivum L. subsp. aestivum | North Dakota, United States | NSGC |  | | 2017 | DEVELOPED | | | | | | Breeding material | Resistance to leaf rust (caused by Puccinia triticina Erikss.) was identified in Aegilops neglecta Req. ex Bertol. (2n=4x=28=UnUnMnMn) and a major gene, Lr62, was subsequently transferred to wheat chromosome 6A. The original translocation consisted of an almost complete Ae. neglecta chromosome fused to a small wheat 6AL telomeric chromosome segment. Following homoeologous chromosome pairing induction, 41 smaller translocations that each retained Lr62 were obtained. Physical and genetic mapping results suggested that Lr62 is located towards the 6AS telomere in the original translocation. Following simple sequence repeat (SSR) marker analyses and genomic in situ hybridization of the recombinants, it appeared that three of four translocations that retained the least Ae. neglecta chromatin were located at the 6AS telomere whereas the fourth recombinant (Lr62-129) was substantially shorter than the other three, and had been relocated to 6BS. In recombinant Lr62-129, the introgressed region included an Xdupw217 (SSR marker) homoeo-locus (251 bp allele) that had replaced the common wheat Xdupw217 locus on 6BS and thus can be used as a co-dominant marker. Lr62-129 exhibited potentially broad-based resistance in seedling tests yet has not previously been used in breeding. Based on its broad major gene resistance, its similar location at a group 6 chromosome short arm telomere, and close proximity to the Xdupw217 marker locus, Lr62 could be a homoeo-locus of Lr53, Lr56, and Lr59. [See PI 682091 - 682094 for accessions from the same JPR publication.] | 1949930 | PI 682094 |