Abiotic Stress and Agronomic Traits
Root Biomass and Drought ToleranceWe thank Paul St. Amand, Guihua Bai, Gina Brown-Guedira, Bob Graybosch and Javier Zuñiga for their contributions to this section.
Drought is one of the most important environmental challenges growers have to face around the world. Droughts are the cause for large grain losses every year, especially in developing countries, and the current trend in global climate change will likely lead to further losses.
Many loci seem to be involved in water stress tolerance in cereals, as suggested by QTL analysis in rice (1) and wheat (2) and EST mapping combined with QTL analysis in barley (3).
Foulkes et al. (4) screened three physiological parameters in several UK wheat lines under irrigated and non-irrigated conditions: water soluble carbohydrates (WSC) accumulation in stems, flowering date and percent of green flag leaf area (%GFLA) persistence. Stem WSC accumulation was positively correlated with grain yield under both conditions, irrigation and non-irrigation. In another study Foulkes et al. (5) indicated that accumulation of WSC in a set of UK cultivars was associated with the presence of the a rye translocation in wheat, 1BL.1RS. However, the variable showing the higher (positive) correlation with grain yield under drought was %GFLA persistence. In a previous work, Verma et al. (6) found two QTLs related to %GFLA persistence, one located on chromosome 2B, which shows a significant effect under normal watering, and another that becomes significant under drought, located on chromosome 2B.Rye translocations
Rye translocations have been extensively used in wheat breeding, especially those involving the short arm of rye chromosome 1R (1RS), because they provide resistance to insects, diseases and reported improvements in yield potential and water-use efficiency. However, the effects on yield and drought tolerance have been highly dependent upon genetic background and environmental conditions. For a summary of experiments see Singh et al. (7) and Ehdaie et al (8). For example, Singh et al. (7) studied the effect of the 1BL.1RS rye translocation in spring wheat line 'Seri 8' under normal moisture and simulated water-stress conditions. Under normal watering conditions, mean grain yield of the 1B control lines was significantly higher than that of the lines carrying the 1BL.1RS, while under water stress there were no significant differences. Ehdaie et al. (8) showed that the presence of the 1RS translocation in spring cultivar 'Pavon' correlated with the presence of a larger root biomass and higher grain yields especially under well watered conditions. All in all, breeders should pay careful attention to the effects of genetic background and environment on drought tolerance of lines potentially conferred by rye translocations.
The methods section describes several protocols for detecting both common types of 1RS rye translocations in wheat lines, 1AL.1RS and 1BL.1RS.
1. Saturation mapping of QTL regions and identification of putative candidate genes for drought tolerance in rice. Nguyen TTT, Klueva N, Chamareck V, Aarti A, Magpantay G, Millena ACM, Pathan MS, Nguyen HT. In: Molecular and General Genomics, 2004, 272: 35-46. [abstract]
2. A high-density genetic map of hexaploid wheat (Triticum aestivum L.) from the cross Chinese Spring x SQ1 and its use to compare QTLs for grain yield across a range of environments. Quarrie SA, Steed A, Calestani C, Semikhodskii A, Lebreton C, Chinoy C, Steele N, Pljevljakusic D, Waterman E, Weyen J, Schondelmaier J, Habash DZ, Farmer P, Saker L, Clarkson DT, Abugalieva A, Yessimbekova M, Turuspekov Y, Abugalieva S, Tuberosa R, Sanguineti M-C, Hollington PA, Aragués R, Royo A, Dodig D. In: Theoretical and Applied Genetics, 2005, 110:865-880. [abstract]
3. Identification of drought-inducible genes and differentially expressed sequence tags in barley. Diab AA, Teulat-Merah B, This D, Ozturk NZ, Benscher D, Sorrells ME. In: Theoretical and Applied Genetics, 2004, 109: 1417–1425. [abstract]
4. Traits for improved drought tolerance of winter wheat in the UK . Foulkes MJ, Verma V, Sylvester-Bradley R, Weightman R, Snape JW. In: Proceedings of the 4th International Crop Science Congress. Brisbane, Australia, 2004. [Congress link]
5. The ability of wheat cultivars to withstand drought in UK conditions: formation of grain yield. Foulkes MJ, Scott RK, Sylvester-Bradley R. In: Journal of Agricultural Science, 2002, 138:153–169. [abstract]
6. Mapping quantitative trait loci for flag leaf senescence as a yield determinant in winter wheat under optimal and drought-stressed environments . Verma V, Foulkes MJ, Worland AJ, Sylvester-Bradley R, Caligari PDS, Snape JW In: Euphytica, 2004, 135:255–263. [abstract]
7. Agronomic effects from chromosome translocations 7DL.7Ag and 1BL.1RS in spring wheat. Singh RP, Huerta-Espino J, Rajaram S, Crossa J. In: Crop Science, 1998, 38:2733. [abstract]
8. Root biomass, water-use efficiency, and performance of wheat-rye translocations of chromosomes 1 and 2 in spring bread wheat 'Pavon'. Ehdaie B, Whitkus RW, Waines JG. In: Crop Science, 2003, 43:710-717. [abstract]
9. Generation of PCR-based Markers for the Detection of Rye Chromatin in a Wheat Background. Koebner RMD. In: Theoretical and Applied Genetics, 1995, 90:740-745. [abstract]
10. Development of simple sequence repeat markers in rye (Secale cereale L.). Saal B, Wricke G. In: Genome, 1999, 42:964-972. [abstract]