Crop improvement and evaluation of water use efficiency by wheat: an integrated approach using stable isotopes

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• Celestin Ukozehasi
• Friday 18 January 2013, 13:00-13:30
• Department of Plant Sciences, Large Lecture Theatre.

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Plant breeding for improved environmental stress tolerance has primarily relied upon traditional selection methods, augmented by marker assisted selection and some high-throughput physiological methodologies. Of the latter, stable isotopes of carbon (13C/12C) and oxygen (18O/16O) offer insights into the balance between stomatal regulation of gas exchange and overall leaf water balance, with organic material providing an integrated history of leaf performance. Recently, two varieties of wheat have been brought to the market as a result of using selection for drought tolerance and yield stability informed by carbon isotopes (CSIRO: Drysdale and Rees), and using δ13C and δ18O in combination offers additional insights into carbon and water balance of leaves under similar environmental conditions. Other more labour intensive methods can be used to provide a snapshot of short-term limitations, such as photosynthetic gas exchange and water relations, and this study set out to explore how well these proxies relate to more long-term isotopic markers, and as compared to leaf anatomical traits.

In this preliminary programme, photosynthetic and hydraulic characteristics, leaf morphology, flowering and yield measurements were collected on 23 recombinant inbred lines of Rht cultivars grown in the field at the National Institute of Agricultural Botany. Having ranked a number of traits according to likely physiological associations, there was a good correlation between carbon isotope composition (∆13C) and instantaneous water use efficiency (WUEi), and that Specific Leaf Area (cm² g⁻¹) could be used as surrogate measure of ∆13C. There were also interesting associations between leaf hydraulic supply and stomatally-led evaporative demand. We also found that there might be a trade-off for selecting WUEi, earliness of flowering and yield. The research will continue by evaluating resource dynamics in the semi-dwarf phenotypes (RhtNILs in a Mercia background), comparing carbon and nitrogen allocation and water use as a function of straw shortening. These methods will also be used to evaluate the performance of Rwandan wheat cultivars under field conditions.

This talk is part of the Plant Sciences Research Seminars series.

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