Registration of Two Synthetic Hexaploid Wheat Germplasms Resistant to Hessian Fly

Two spring-habit synthetic hexaploid wheat (SHW) (3Aegilotriticum spp., 2n 5 6x 5 42, AABBDD genomes) germplasms SW8 (Reg. no. GP-803, PI 639730) and SW39 (Reg. no. GP-804, PI 639732) with resistance to Hessian fly [Mayetiola destructor (Say)] were released by the USDA-ARS, Fargo, ND, and the North Dakota State Agricultural Experiment Station, Fargo, ND, in 2004. The two SHW lines, SW8 and SW39, were originally developed in the 1980s by USDA-ARS Research Geneticist L.R. Joppa. ‘Langdon’ (CItr 13165) durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn., 2n5 4x5 28, AABB] was used as the female and crossed with two accessions ofAegilops tauschii Cosson (2n 5 2x 5 14, DD), CIae 25 (accession number of USDA National Small Grains Collection, Aberdeen, ID) and RL 5561 (accession number of Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, MB), for SW8 and SW39, respectively. The F1 hybrids from the two crosses had 21 chromosomes but they were partially fertile, probably due to the formation of functional unreduced gametes as reported in the F1 hybrid to ‘Largo’ (CItr 17895), a SHW line described by Joppa and Williams (1982). Five F2 plants from each cross were initially grown in a greenhouse for seed increase. In the F3 and latter generations, only the seed from a single plant with highest seed set were used for seed increase. The seed from the cross of Langdon/CIae 25 was bulked in the F4 generation to form SW8 and the seed from Langdon/RL 5561 was bulked in the F6 generation to form SW39. Since the SHW lines were developed by spontaneously doubling the chromosomes of triploid plants with ABD genomes, they are highly homogenous. However, some aneuploid plants with chromosome number other than 42 may occur due to unpaired chromosomes in a small number of pollen and egg mother cells as reported in the Largo SHW line (Joppa and Williams, 1982). These two SHW lines and their durum parent Langdon were evaluated for resistance to the Great Plains (GP) biotype of Hessian fly. The hard red spring wheat (T. aestivum L.) ‘Reeder’ was included as a susceptible control in the evaluation. Five plants of each genotype were infested with 15 to 20 Hessian fly eggs at the oneto two-leaf stage and plant and insect reactions were evaluated 15 d later. Normal plants with dead larvae at the crown were classified as resistant. Stunted plants with growing larvae at the crown were classified as susceptible. All infested plants of Reeder and Langdon were stunted and had approximately 4 to 30 live larvae per plant. All plants of SW8 and SW39 had normal growth without any live larvae. The results indicated that SW8 and SW39 were resistant to GP biotype whereas Langdon was susceptible, suggesting that the resistance in the SHW lines was controlled by the gene(s) on the D-genome chromosomes from A. tauschii. A total of 31 resistance genes to Hessian fly have been identified in wheat and related species (McIntosh et al., 2003; Williams et al., 2003). Five of them, H13 (6DL), H22 (1D), H23 (6DL), H24 (3D), and H26 (4D), were derived from A. tauschii (McIntosh et al., 2003). The resistance gene H13 has been deployed in a soft winter wheat cultivar, INW9811, which is adapted to the mid-South region of the eastern United States (Ratcliffe et al., 2000). Our preliminary data from molecular mapping and allelism tests suggested that resistance in SW8 was conferred by a gene different from H13 in Molly (PI 562619), H22 in KS86WGRC1 (PI 499691), H23 in KS89WGRC3 (PI 535766), and H24 in KS89WGRC6 (PI 535769). Allelism of the resistance gene in SW8 with H26 in KS92WGRC26 (PI 572542) is under determination. The resistance gene in SW39 was different fromH13,H22,H24,H26, and the resistance gene in SW8 based on allelism tests. The allelism test of the resistance gene in SW39 with H23 in KS89WGRC3 (PI 535766) is in progress. SW8 and SW39 are both non-free threshing and have late maturity. SW8 and SW39 headed on July 20 and July 18 in 2004 in Fargo, ND, respectively (approximately 2–3 wk later than most currently grown hard spring wheat cultivars in North Dakota). SW8 was taller than SW39 in plant height and they averaged 109 and 83.2 cm in height, respectively, measured in the field in Fargo in 2004. SW8 plants had normal fertility and set plump seed. The majority of SW39 plants had low seed set and the seed was usually shriveled. SW8 and SW39 were previously evaluated for their resistances to several economically important diseases, including tan spot [caused by Pyrenophora tritici-repentis (Died.) Drechs.], Stagonospora nodorum blotch (SNB) [caused by Stagonospora nodorum (Berk.) Castell. and Germano], leaf rust (caused by Puccinia triticina Eriks.), stem rust (caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. and E. Henn.), and Fusarium head blight (FHB) (caused by Fusarium graminearum Schwabe) (Friesen et al., 2003; Oliver et al., 2005). Friesen et al. (2003) reported that these two SHW lines were resistant to seven stem rust races (pgt-TPMK, JCMN, RTQQ, TPPK, QTHJ, MCCF, and HKHJ), moderately resistant to tan spot race 1 at the seedling stage and to leaf rust race MCDL in adult plant stage. Both SHW lines were susceptible to a standard field isolate of SNB and two leaf rust races (MCDL and THBJ) at the seedling stage. Oliver et al. (2005) evaluated SW8 and SW39 for resistance to the spread of FHB in the head using three pathogenic strains of F. graminearum and observed that SW8 and SW39 were susceptible to the disease. Limited quantities of seed of each germplasm are available from the corresponding author. Seed samples (3 g) of each SHW lines will be distributed onwritten request. It is requested that appropriate recognition of its source be made if these germplasms contribute to the development of a new breeding line, germplasm, or cultivar.