Evaluation in barley lines of a simple pollen method for breeding for drought tolerance in wheat

Abstract

A pollen test, which is used in wheat to detect an osmoregulation gene, was evaluated in 16 barley doubled-haploid lines. In the presence of water stress, created using a 40% polyethylene glycol 6000 solution on microscope slides, the application of a low concentration of KCl produced a size response in approximately 50% of lines. Visual selection was confirmed by quantification in 8 lines, with significant responses in 5. The lines were then evaluated in the field in low and high soil-water deficit sites. Water deficit was produced by exclusion of rain after initially wetting up the soil profile. The group selected for a pollen response showed significantly lower leaf zero turgor water potentials (ie. greater turgor maintenance). This was, in turn, due to differences in osmoregulation. At ear emergence, mean turgor pressures at low deficit and mean relative water contents at high deficit were higher in lines with high pollen osmoregulation. There was also a separate effect due to differences in maturity between the lines. Higher turgor maintenance and osmoregulation occurred in lines with faster maturity. Because lines were dissimilar, accurate dry weight and yield comparisons between osmoregulation groups were not feasible. A drought susceptibility index was used to accommodate variation in low stress growth and yield, and to allow comparisons with wheat experiments. In all experiments high osmoregulation groups had lower mean values than low groups. Indices calculated for osmoregulation groups in barley were not significantly different to those from similar wheat experiments conducted over 4 seasons with differing evaporative demand, suggesting operation of a similar process or gene. Further confirmatory work is needed using more closely related lines.