Control of late maturity alpha-amylase in wheat by the dwarfing gene Rht-D1b and genes on the 1B/1R translocation

The occurrence of late maturity alphaamylase (LMA) was investigated using two doubledhaploid wheat populations segregating for the dwarfing gene Rht-D1b and the 1B/1R translocation. Genotypes were assessed in the field and in controlled environments where a cold-shock treatment was used to induce LMA. Results from field-grown genotypes from the cross Spark 9 Rialto suggest that the absence of Rht-D1b or the presence of the 1B/1R translocation increases the expression of LMA.These two genetic factors were found to act independently and to have a positive interaction (complementary epistasis). In Option 9 Potent genotypes fixed forRht-D1b, the 1B/1R effect was similar to that seen in the equivalent Spark 9 Rialto genotypes. Under controlled environment conditions, genotypes with the 1B/1R translocation showed a higher occurrence of LMA under both control and cold-shock conditions. 1B/1R was present in the majority of genotypes expressing LMA under control and cold-shock conditions.The results point to the novel finding that the 1B/1R translocation increases the expression of alphaamylase in LMA-prone germplasm independently of effects of Rht-D1b, whereas previously it had been thought to act by a modification of the Rht-D1b effect.