Late maturity α-amylase (LMA) refers to the synthesis of high isoelectric point (pI) α-amylase during the middle- to latestages of grain fill, in the absence of pre-harvest sprouting, within the aleurone layer of bread wheat (Triticum aestivum L.), durum wheat (T. durum) and synthetic hexaploid wheat. During LMA expression, α-amylase accumulates and is retained within harvested grain with little to no impact on starch quality. Alpha-amylase activity is detected by the Hagberg Falling Number, an international standard of grain quality used by grain traders for grain quality classification. Since wheat is traded on Falling Number, Wheat classification in Australia requires new varieties to pass two-rounds of LMA screening prior to quality classification to avoid potential losses to wheat growers. Here we present a research project designed to investigate four important aspects of LMA expression, and their impact on wheat breeding and wheat quality.

Firstly, to develop a high-throughput phenotypic screen for LMA expression in a controlled environment setting, in an attempt to avoid tiller detachment and cold shock currently used. This will help improve phenotypic selection against LMA expression while also reducing cost of pre-classification assessment and LMA genetic research. Secondly, to identify how LMA expression in the LMA screen relates to field expression and the risk of low Falling Number as a result. A diverse set of bread wheat lines are being grown in a field trial across Australian wheat growing regions between 2014 and 2019 to analyse genotype by environment effects. Thirdly, to identify and validate genetic marker(s) associated with LMA expression, which will facilitate a reliable and robust screening methodology for LMA expression. A region on chromosome 7B near the boron tolerance gene (Bo1), in addition to the gibberellin insensitive reduced height genes (Rht-B1b and RhtD1b), are known to reduce LMA expression. A key question remains as to whether gibberellin sensitive Rht13 and Rht18, in addition to a previously reported 3B LMA locus, have a commercially significant impact on LMA expression. Lastly, to examine the effects of LMA on end-use quality, since the little research that has been performed suggests very limited effects of low Falling Number as a result of LMA expression on end-product quality. This research will reduce the cost of LMA screening, thereby increasing rates of genetic gain for low LMA expression, while also assisting the Australian wheat industry to adopt robust methods of LMA risk mitigation.