Some effects of genetic variation in drought-induced abscisic acid accumulation on the yield and water use of spring wheat

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Abstract
Selection for high-(H) and low-(L) drought-induced abscisic acid (ABA) accumulation in spring wheat was made from a cross between parents which contrasted in the character. By the F5 generation H and L selections were homozygous for ABA accumulation, which differed between the classes by 80%. The selections were evaluated in field experiments in which the amount of available water was varied.In one experiment, in which plots were automatically sheltered from rain, H selections outyielded L selections by an average 0·36 t/ha both when fully irrigated and when water was withheld between anthesis and maturity. The extra grain yield of the H selections was not produced at the expense of additional water requirement in either treatment. When water was withheld during the 4 weeks preceding anthesis, the grain yields of H and L selections were similar, but H selections used less water between 1 May and maturity. Averaged over all treatments the ratio of grain yield to water use was greater for H selections than for L selections by 0·12 t/ha/100 mm. Withholding water caused a reduction in water use and a corresponding reduction in biomass production in both sets of selections.In two trials in which plots were either irrigated weekly or received natural rainfall only, the ratio of grain yield to water use was again greater for H than for L selections, by an average 0·10 t/ha/100 mm.It is concluded that in spring wheat, selection for high levels of ABA accumulation in response to water stress may provide an opportunity of increasing grain yield and water-use efficiency.