Complete: Selection methods for the improvement of drought tolerance and water use efficiency in sugar beet

Timescale: 2006
Project Lead: Unknown
Project Sponsor: BBRO

Project Summary

In 2006, 27 genotypes were tested under irrigated and managed drought conditions using the polytunnel system. These genotypes consisted of six ‘core’ hybrids that have been tested over several years and are known to contrast for drought tolerance and water use efficiency. The best of these (KWS4-03) showed greater drought tolerance than the benchmark variety Cinderella. However, in a bid to discover new germplasm with a greater range of responses, 200 testcross hybrids from KWS were tested in observation plots 2004. A subset of these was tested in replicated plots in 2005, and a further subset was tested a second year in 2006. The result, shown here, is 11 testcross genotypes that show low and high drought tolerance, including some that show significantly greater drought tolerance than genotypes studied previously. In addition, ten genotypes from Strube Dieckmann were tested. None of these had been evaluated for drought tolerance previously. Some of these genotypes showed exceptional drought tolerance and yield potential. Characterisation of these materials help us learn more about what characters contribute to drought tolerance, and inform the breeder which germplasm tends to be more successful.

Main Objectives

Water use efficiency The differences between genotypes in the way they use water to form yield (the water use efficiency, or WUE) are related to growth potential more than differences in actual water use. Hence, genotypes that yield poorly, but use similar amounts of water to other more high yielding genotypes, essentially waste water. Breeders would like to eliminate these types from their advanced breeding pool. Carbon isotope discrimination ratio (CID) was inversely related to WUE, but the correlation was not as strong as that observed in previous experiments. Data from a lysimeter experiment designed to measure water use efficiency more accurately than in field experiments were not reliable because plants became too stressed during unusually hot weather in July. However, much was learned about how to do these types of experiments. Secondary traits Traits that are associated with drought tolerance and water use efficiency, but are easier and cheaper to measure, could be useful selection criteria in breeding programmes. We studied a number of morphological and physiological traits that have shown promise in previous studies. New ways of measuring stomatal conductance and specific leaf weight were 2 investigated, and improvements in techniques were made. We field-tested and calibrated a new viscous flow porometer, which should be a useful tool for assaying transpiration capacity, as measurements can be made rapidly on a large number of plants. 

Outcomes / Key Message For Growers And Industry

Conclusions These experiments fulfilled the objectives of confirming the ranking of an extended and more diverse set of genotypes than had previously been examined. These genotypes will be useful tools in on-going studies. The relationships between secondary traits and water use efficiency were further elucidated, but the strength of the correlations are not yet strong enough to warrant their immediate use by breeders as indirect selection criteria for drought tolerance or water use efficiency. We have discovered extensive genotypic variation for carbon isotope discrimination ratio, and this trait could be directly applied in breeding programmes for water use efficiency.

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