Genetics of Na(+) exclusion and salinity tolerance in Afghani durum wheat landraces

Bakground: Selecting for low concentration of Na⁺ in the shoot provides one approach for tackling salinity stress that adversely affects crop production. Novel alleles for Na⁺ exclusion can be identified and then introduced into elite crop cultivars. Results: We have identified loci associated with lower Na⁺ concentration in leaves of durum wheat landraces originating from Afghanistan. Seedlings of two F₂ populations derived from crossings between Australian durum wheat (Jandaroi) and two Afghani landraces (AUS-14740 and AUS-14752) were grown hydroponically and evaluated for Na⁺ and K⁺ concentration in the third leaf. High heritability was found for both third leaf Na⁺ concentration and the K⁺/Na⁺ ratio in both populations. Further work focussed on line AUS-14740. Bulk segregant analysis using 9 K SNP markers identified two loci significantly associated with third leaf Na⁺ concentration. Marker regression analysis showed a strong association between all traits studied and a favourable allele originating from AUS-14740 located on the long arm of chromosome 4B. Conclusions: The candidate gene in the relevant region of chromosome 4B is likely to be the high affinity K⁺ transporter B1 (HKT1;5-B1). A second locus associated with third leaf Na⁺ concentration was located on chromosome 3BL, with the favourable allele originating from Jandaroi; however, no candidate gene can be identified.Nawar Jalal Shamaya, Yuri Shavrukov, Peter Langridge, Stuart John Roy and Mark Teste

Salinity tolerance and Na+ exclusion in wheat: Variability, genetics, mapping populations and QTL analysis

Also published as a book chapter: Proceedings from the 8th International Wheat Conference and BGRI 2010 Technical Workshop, 30 May-4 June 2010, St. Petersburg, RussiaA wide range of variability in both Na+ exclusion and salinity tolerance was shown in Triticum dicoccoides and the best performing genotype, from Getit, was identified for further study and for crossing. In bread wheat, plants BC6F1 from the cross Chinese Spring/line SQ1 showed less variability, but the line 1868 was identified as a potential source of tissue tolerance to salinity. Two Afghani durum landraces were identified among 179 screened, with approximately 50% lower Na+ accumulation in shoots. Genetic analysis of F2 progenies between landraces and durum wheat showed clear segregation indicating on the single, major salinity tolerance gene in the landraces. Further genetic and molecular analysis of the candidate gene and its localization is in the progress. QTL analysis of two non-pedigree related mapping populations of bread wheat, Cranbrook × Halberd and Excalibur × Kukri, showed one QTL in each population on the same region of chromosome 7AS, independent of year or growing conditions (both supported hydroponics and field trials), and a novel gene is expected to be associated with this QTL.Y. Shavrukov, N. Shamaya, M. Baho, J. Edwards, C. Ramsey, E. Nevo, P. Langridge and M. Teste

Salt tolerance in Argentine wheatgrass is related to shoot sodium exclusion

This is the first report about Na and K fluxes and heritability of Na exclusion in the Elymus genus. Argentine wheatgrass (Elymus scabrifolius ) is an important forage genetic resource for saline environments. A previous study had shown salt‐sensitive lines accumulated toxic levels of Na in shoots. The aim of this study was to increase the understanding of Na exclusion in Argentine wheatgrass. Growth and Na and K accumulation rates were analyzed in two homozygous salt‐tolerant genotypes (T1 and T2) and a salt‐sensitive one (S1), under different salt stress levels. The Na accumulation rate in shoots was 1.5 times higher in the sensitive line than in the tolerant ones at 100 mM NaCl, and 5 times higher at 200 mM NaCl. A negative association was found between Na concentration and leaf weight in parent genotypes, F1 and segregating F2 population generated by crossing homozygous S1 and T2, suggesting that growth in the third leaf was more affected in Na‐including genotypes. The inheritance of Na exclusion was estimated under salt stress conditions in a segregating F2 population and in F2:3 families obtained by crossing two homozygous genotypes with contrasting values of shoot sodium exclusion. In F2 population and F2:3 families, Na concentration segregation was compatible with intermediate inheritance (with very low partial dominance). High heritability values estimated for Na exclusion suggest that this trait might be used as a priority selection criterion for salt tolerance. Results will be useful to design breeding strategies for salt tolerance in this and related species of the Elymus genus.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Zabala, Juan Marcelo. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Programa de Documentación, Conservación y Valoración de la Flora Nativa; Argentina. Consejo de Investigaciones Científicas y Técnicas; ArgentinaFil: Marinoni, Lorena del Rosario. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Programa de Documentación, Conservación y Valoración de la Flora Nativa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; Argentina. Consejo de Investigaciones Científicas y Técnicas; ArgentinaFil: Ribero, Gustavo. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias; ArgentinaFil: Schrauf, Gustavo Enrique. Universidad de Buenos Aires. Facultad de Agronomía; Argentin