Registration of Five Wheat Isogenic Lines for Leaf Rust and Stripe Rust Resistance Genes

Abstract

Published online January 24, 2006 REGISTRATIONS Registration of Five Wheat Isogenic Lines for Leaf Rust and Stripe Rust Resistance Genes We report here the release of four germplasm lines of hard red spring (HRS) wheat (T. aestivum L.) [Yecora Rojo Yr36– Gpc-B1 (Reg. no. GP-793, PI 638740), Yecora Rojo Lr47 (Reg. no. GP-791, PI 638738), Kern Lr47 (Reg. no. GP-792, PI 638739), and Anza Lr37/Yr17/Sr38 (Reg. no. GP-795, PI 638742)] and one durum wheat (T. turgidum L.) [UC1113 Yr36– Gpc-B1 (Reg. no. GP-794, PI 638741)], isogenic for leaf rust (Puccinia triticina Eriks.) resistance gene Lr47, stripe rust (P. striiformis West. f. sp. tritici) resistance gene Yr36, and the Lr37/Yr17/Sr38 leaf, stripe, and stem rust (P. graminis Pers.: Pers. f. sp. tritici Eriks. & E. Henn.) resistance gene complex. All genes were transferred by six backcrosses to their re- spective recurrent parents and molecular markers for each gene were used to select heterozygous plants for the targeted genes. After the sixth backcross plants were self-pollinated and homozygous BC 6 F 2 plants were selected using markers. The isogenic lines are expected to be more than 99% identical to their recurrent parents. Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. Isogenic Lines for Stripe Rust Resistance Gene Yr36 and Grain Protein Content Gene Gpc-B1 Chromosome 6B from T. turgidum ssp. dicoccoides (Ko rn.) Thell. accession ‘FA15–3’ from Israel (DIC hereafter) carries a gene that significantly increases grain protein content (Cantrell and Joppa, 1991). This gene was initially mapped as a quantitative trait locus within a 30-cM region of the short arm of chromosome 6BS using Recombinant Substitution Lines (RSLs) of the DIC 6B chromosome in the genetic back- ground of Langdon (Joppa et al., 1997). The same DIC chro- mosome segment was found in the hexaploid wheat variety ‘Glupro’ (‘Columbus’/T. turgidum var. dicoccoides//‘Len’) (Khan et al., 2000; Mesfin et al., 1999). The gene responsible for the differences in grain protein content was mapped as a single locus designated Gpc-B1 proximal to the Nucleolar Organizer Region (Olmos et al., 2003; Distelfeld et al., 2004). During field evaluations of the RSLs at University of California (UC) at Davis (Olmos et al., 2003), we observed that the lines with the DIC segment were more resistant to stripe rust than the lines with the Langdon segment. Two RSLs with the DIC 6BS region and two with the Langdon region were evaluated under controlled conditions at Washington State University. At the seedling stage, all lines were sus- ceptible to the 15 different stripe rust races tested (including new races PST100 and PST101), but when the same lines were evaluated at the adult plant stage under a high-temperature cycle, the lines carrying the DIC segment showed significantly lower infection types (IT: 2.0 to 2.3) than the lines with the Langdon segment (IT: 7.0 to 7.3) with races PST100 and PST101. This high-temperature adult plant resistance gene was mapped as a single locus designated Yr36 (McIntosh et al., 2005). Yr36 was mapped on chromosome 6BS, 2 to 4 cM proximal to the Gpc-B1 gene (Uauy et al., 2005). Distal molecular markers Xucw74 and proximal markers Xucw77 or Xbarc136 were used to introgress Yr36 and Gpc-B1 into the HRS common wheat variety ‘Yecora Rojo’ CItr 17414 (Qualset et al., 1985) using Glupro as a donor parent; and into the durum breeding line UC1113 (UC Davis selection from CIMMYT cross CD52600 [KIFS//RSS/BD1419/3/MEXIS-CP/ 4/WAHAS/5/YAV79]) using Langdon RSL#65 as a donor parent. The BC 6 F 3 seeds of the homozygous lines were de- posited at the National Small Grains Collection (NSGC) as Yecora Rojo Yr36– Gpc-B1 and UC1113 Yr36– Gpc-B1. These isogenic lines have been designated as the type germplasm for the Yr36 gene in T. aestivum and T. turgidum respectively (McIntosh et al., 2005). The two pairs of isogenic lines were compared in field trials in Madera, CA, and Davis, CA, in 2004 under severe stripe rust infection pressure using a split plot design with five rep- lications and large plots (1.2 by 4.0 m in Davis and 1.5 by 4.0 m in Madera). Lines with and without Yr36– Gpc-B1 showed no significant differences in height and heading time for both the tetraploid and hexaploid pairs of isogenic lines. The Yecora Rojo Yr36-Gpc-B1 line showed a significant reduction in stripe rust infections (from 87 to 51% severity, Davis P 5 0.20, Madera P , 0.0009), higher yields (average increase of 970 kg ha 21 , Davis P 5 0.05, Madera P 5 0.02), and an average increase of 850 g protein per 100 kg of grain relative to the isogenic line without the DIC 6BS chromosome segment (from 13.2 to 14.1% protein content, Davis P 5 0.03, Madera P 5 0.0007). Test weights of the lines with the Yr36- Gpc-B1 genes (79.3 6 0.5 kg hL 21 ) and without these genes (78.8 6 0.9 kg hL 21 ) were not significantly different in this experiment. The UC1113 Yr36-Gpc-B1 line showed a significant re- duction in stripe rust severity (from 36 to 2% severity, Davis P 5 0.03, Madera P 5 0.006), slightly higher yields (average increase of 242 kg ha 21 , although not significant in both loca- tions), and an average increase of 1100 g of protein per 100 kg of grain relative to the isogenic line without the DIC 6BS chro- mosome segment (from 13.5 to 14.5% protein content, Davis P = 0.006, Madera P , 0.0001). Test weights of the lines with the Yr36-Gpc-B1 genes (80.1 6 0.5 kg hL 21 ) and without these genes (81.0 6 0.5 kg hL 21 ) were not significantly different in this experiment. Isogenic Lines for Leaf Rust Resistance Gene Lr47 The interstitial translocation line T7AS-7S#1–7ASA7AL carrying Lr47 from T. speltoides (Tausch) Gren. was originally transferred to bread wheat by irradiating hybrid seed (CI15092/T. speltoides//‘Fletcher’/3/5* ‘Centurk’) with fast neu- trons (Wells et al., 1982). Interstitial segments of chromosome 7S#1 were transferred to chromosome 7A of hexaploid wheat using the ph1b mutation that promotes homeologous recom- bination (Lukaszewski 1995). The interstitial translocations were backcrossed three times into hard white spring variety ‘Pavon 76’ (PI 519847) and plants homozygous for the inter- stitial translocation were released as germplasm PI 603918 (Lukaszewski et al., 2000). Resistance gene Lr47 for leaf rust conferred resistance to the leaf rust races TBT, NBB, MBR, LCG, SDJ, MBG, NDB, MCG, and TDD (PRT codes, Long and Kolmer, 1989). The T. speltoides segment is located 2 to 10 cM from the centro- mere and is 20 to 30 cM long (Dubcovsky et al., 1998). This segment is generally transferred as a single linkage block. Here we report the transfer of the Lr47–T. speltoides segment from Pavon 76 into HRS varieties Yecora Rojo and ‘Kern’ (PI 612142) using molecular markers (Helguera et al., 2000). The BC 6 F 3 seeds of the homozygous lines were deposited at the National Small Grains Collection (NSGC) as Yecora Rojo Lr47 and Kern Lr47. The two pairs of isogenic lines were com- pared in field trials at Kings, CA, in 2003 and Kings and UC Davis, CA, in 2004 using a split plot design with four replica- tions [plot size (1.2 by 4.0 m in Davis and 1.5 by 4.0 m in Kings)]. Isogenic lines with and without the gene showed similar agro- nomic characteristics including height and heading time. De- pending on the environment, some of the plants carrying the Lr47 chromosome segment showed purple stems in some plants. No significant differences in yield between isogenic lines with and without the Lr47 gene were detected at Kings. How-