Expression of late maturity alpha-amylase in wheat containing gibberellic acid insensitivity genes

Two wheat cultivars, Spica and Lerma 52, which consistently produce high levels of alpha-amylase during the later stages of grain development (late maturity alpha-amylase), were crossed with a set of four near-isogenic lines carrying the tall (rht) allele or one of the dwarfing genes Rht1, Rht2 or Rht3 (GA-insensitive alleles). The F-1 and F-2 populations were developed and analysed for grain alpha-amylase and plant height. The Rht3 gene exhibited the strongest influence on plant height and strongly inhibited new alpha-amylase synthesis during the later part of grain ripening. By comparison, Rht1 and Rht2 had a less pronounced effect but still significantly reduced the expression of late maturity alpha-amylase. These observations suggest that gibberellic acid is involved either directly or indirectly in this phenomenon. The implications of the effect of dwarfing genes on expression of late maturity alpha-amylase are discussed in relation to cultivar improvement and to the identification and control of high alpha-amylase germplasm.