Disease resistance. Leaf rust
Lr21
References
1. Leaf rust-resistance genes Lr41, Lr42 and Lr43 transferred from Triticum tauschii to common wheat. Cox, T.S.; Raupp W.J.; Gill, B.S. In: Crop Science, 1994, 34(2):339-343.
In order to diversify the genetic base of resistance in hard red winter wheat (Triticum aestivum L.) to leaf rust (caused by Puccinia recondita Rob. ex Desm.), five genes for resistance were transferred from the diploid goatgrass T. tauschii (Coss.) Schmal. to hexaploid wheat lines. One of the derived lines, KS90WGRC10, had a very low infection type when inoculated with 23 cultures of P. recondita. The others, KS91WGRC11, KS92WGRC16, U1865, and U1866, had low to intermediate infection types with three cultures. Their infection types varied similarly to those of lines carrying previously transferred alleles of Lr21. WGRC10 carries a completely dominant gene, Lr41, on chromosome ID that segregates independently of any other T. tauschii-derived leaf rust-resistance genes. WGRC11 carries the partially dominant gene, Lr42, also on ID, that is linked to Lr21 with a recombination value of 0.286 +- 0.023. WGRC16 carries a partially dominant gene, Lr43, that segregates independently of all known genes for seedling resistance from T. tauschii; its chromosome location is not known. The genes carried by U1865 and U1866 are allelic to Lr21. WGRC10, WGRC11, and WGRC16 have been released as germplasms by the Wheat Genetics Resource Center.
2. Chromosome location of leaf rust resistance gene Lr43 from Aegilops tauschii in common wheat. Hussien, T.; Bowden, R.L.; Gill, B.S.; Cox, T.S. In: Crop Science, 1997, 37(6):1764-1766.
Wheat leaf rust resistance gene Lr43 was recently transferred from Aegilops tauschii Coss. to common wheat (Triticum aestivum L.) to produce hard red winter wheat germplasm line KS92WGRC16. Monosomic and telocentric analyses were used to determine the chromosomal and chromosome arm location of Lr43. KS92WGRC16 was crossed with each of the seven D-genome monosomic lines. The F2 families were inoculated with race PBJL of the leaf rust fungus, Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Eriks. & E. Henn.) D.M. Henderson. The number of resistant to susceptible seedlings did not deviate significantly from a 3:1 ratio in crosses involving 1D, 2D, 3D, 4D, 5D, or 6D monosomic lines. However, the 7D monosomic-derived F2 deviated significantly from a 3:1 ratio (chi2 = 32.2, P < 0.001) indicating that Lr43 is located on this chromosome. Twenty resistant F2 plants from the critical cross were progeny tested, and results confirmed the location of Lr43 on chromosome 7D. Telocentric analysis showed that Lr43 is on the short arm of chromosome 7D (7DS) and it is unlinked to the centromere. This information may facilitate development of molecular markers and result in more efficient breeding for resistant cultivars.
3. Inheritance in hexaploid wheat of leaf rust resistance and other characters derived from Aegilops squarrosa. Kerber, E.R.; Dyck, P.L. In: Canadian Journal of Genetics and Cytology, 1969, 11:639-647.
4. An RGA-like marker detects all known Lr21 leaf rust resistance gene family members in Aegilops tauschii and wheat. Huang, L; Gill, B.S. In: Theoretical and Applied Genetics, 2001, 103(6-7):1007-1013.
Leaf rust is one of the most important diseases of wheat worldwide, particularly in the Great Plains region of the USA. One long-term strategy for the control of this disease may be through durable genetic resistance by gene pyramiding. An important step in this strategy is identifying molecular markers linked to different leaf rust-resistance genes. Here we report the molecular tagging of a leaf rust-resistance gene that may have the potential for durable resistance through further genetic manipulation and gene pyramiding. Lr39 was previously designated for a leaf rust-resistance gene introgressed from Aegilops tauschii accession TA1675 into the common wheat germplasm WGRC2. Lr40 was designated for a gene derived from Ae. tauschii accession TA1649 and is present in germplasm WGRC7. These genes are now believed to be allelic to Lr21, which was transferred to wheat from a different accession of Ae. tauschii. Molecular mapping of Lr39 and Lr40 indicates that both genes come from TA1649. WGRC2 and WRGC7 also have a similar infection type against rust culture PRTUS6. We suggest the designation of the gene in WGRC2 should be changed to Lr40. RFLP marker KSUD14 (locus Xksud14) was found 0.2-cM proximal to Lr40 in a WGRC2/Wichita F2 population (218 individuals), and co-segregated with the gene in a WGRC7/Wichita F2 population (165 individuals). A PCR-based molecular marker developed from the sequence-tagged-site (STS) of Xksud14 was mapped to the same locus as the RFLP marker KSUD14 in both populations. KSUD14 has the structure of a resistance gene analog (RGA) including kinase2a and kinase3 domains similar to the Cre3 gene of wheat and the rust resistance gene Rp1-D of maize. When the PCR products amplified from KSU14 STS were cleaved with restriction enzyme MspI, an 885-bp fragment was found in WGRC2, WGRC7, the Lr21 near-isogenic line, and eight accessions of Ae. tauschii shown to have resistance gene alleles at the Lr21 locus. The KSUD14 PCR-based assay provides an excellent marker for Lr40 and Lr21 in diverse wheat breeding and wild Ae. tauschii populations.
5. Evaluation of "sequence-tagged-site" PCR products as molecular markers in wheat. Talbert, L.E.; Blake, N.K.; Chee, P.W.; Blake, T.K.; Magyar, G.M. In: Theoretical and Applied Genetics, 1994, 87(7):789-794.
The polymerase chain reaction (PCR) is an attractive technique for many genome mapping and characterization projects. One PCR approach which has been evaluated involves the use of randomly amplified polymorphic DNA (RAPD). An alternative to RAPDs is the sequence-tagged-site (STS) approach, whereby PCR primers are designed from mapped low-copy-number sequences. In this study, we sequenced and designed primers from 22 wheat RFLP clones in addition to testing 15 primer sets that had been previously used to amplify DNA sequences in the barley genome. Our results indicated that most of the primers amplified sequences that mapped to the expected chromosomes in wheat. Additionally, 9 of 16 primer sets tested revealed polymorphisms among 20 hexaploid wheat genotypes when PCR products were digested with restriction enzymes. These results suggest that the STS-based PCR analysis will be useful for generation of informative molecular markers in hexaploid wheat.