Quantitative trait locus analysis of late maturity alpha-amylase in wheat using the doubled haploid population Cranbrook x Halberd

Mapping of the late maturity alpha -amylase (LMA) gene using quantitative t rait locus (QTL) analysis represents an important step in identification of potential molecular markers that would greatly improve efficiency and accu racy of screening for LMA. QTL controlling the expression of LMA in wheat w ere detected in a doubled haploid (DH) cross/population derived from wheat (Triticum aestivum L. em. Thell) cultivars Cranbrook (LMA source) and Halbe rd (non-LMA). The DH population and parents were sown in replicated trials at Narrabri with sowing times differing by 2 weeks. Cool temperature treatm ent of detached tillers was used to induce expression of LMA in lines carry ing the defect. The number of grains in ripe, treated tillers that containe d high pI (malt, germination type) alpha -amylase isozymes was measured usi ng an ELISA antibody kit highly specific for high pI isozymes. QTL analyses were conducted separately for each sowing, but results from both sowings w ere consistent and indicated that there was a highly significant (P<0.001) QTL on the long arm of chromosome 7B (accounting for 31% of the variation i n the first experiment), with Cranbrook contributing the higher value allel e. A second QTL that accounted for 13% of the variation was found close to the centromere on chromosome 3B. Although it was less important than the QT L on 7B it was nevertheless still significant (P<0.05).