Abstract
Late maturity α-amylase (LMA) and pre-harvest sprouting (PHS) are both recognized as environmentally induced grain quality defects resulting from abnormally high levels of α-amylase. LMA is a more recently identified quality issue that is now receiving increasing attention worldwide and whose prevalence is now seen as impeding the development of superior quality wheat varieties. LMA is a genetic defect present in specific wheat genotypes and is characterized by elevated levels of the high pI TaAMY1 α-amylase, triggered by environmental stress during wheat grain development. TaAMY1 remains present in the aleurone through the harvest, lowering Falling Number (FN) at receival, causing a down-grading of the grain, often to feed grade, thus reducing the farmers’ income. This downgrading is based on the assumption within the grain industry that, as for PHS, a low FN represents poor quality grain. Consequently any wheat line possessing low FN or high α-amylase levels is automatically considered a poor bread wheat despite there being no published evidence to date, to show that LMA is detrimental to end product quality. To evaluate the validity of this assumption a comprehensive evaluation of baking properties was performed from LMA prone lines using a subset of tall non-Rht lines from a multi-parent advanced generation inter-cross (MAGIC) wheat population grown at three different sites. LMA levels were determined along with quality parameters including end product functionality such as oven spring, bread loaf volume and weight, slice area and brightness, gas cell number and crumb firmness. No consistent or significant phenotypic correlation was found between LMA related FN and any of the quality traits. This manuscript provides for the first time, compelling evidence that LMA has limited impact on bread baking end product functionality.
Highlights
Alpha-amylases (EC 3.2.1.1) are endohydrolases that cleave α-1,4 glucosidic bonds breaking down starch macromolecules into smaller polysaccharides
Subsets of tall non-Rht lines taken from a multi-parent advanced generation inter-cross (MAGIC) 4-parent wheat population from the Yanco trial were selected to perform a complete Late maturity α-amylase (LMA) assessment including Stirring Number (SN) converted equivalent Falling Number (eFN), total α-amylase activity assay, ELISA based high pI α-amylase detection kit and real-time quantitative PCR (RT-qPCR) measurement of expression of the transcript expressed in LMA affected wheat, TaAMY1
EFN was significantly negatively correlated with both total α-amylase activity (−0.434, p < 0.001), ELISA Test (−0.492, p < 0.001) and RT-qPCR (−0.318, p = 0.00187)
Summary
Alpha-amylases (EC 3.2.1.1) are endohydrolases that cleave α-1,4 glucosidic bonds breaking down starch macromolecules into smaller polysaccharides. Many biological and industrial processes, such as mammalian digestion, plant metabolism, biofuel production, baking, fermentation, and malting rely on the hydrolysis of native starch by α-amylase (Janecek et al, 2014). Alpha-amylase is considered to be one of the primary enzymes responsible for starch degradation in cereals and wheat. Α-amylase initiates the conversion of starch into simple sugars to fuel embryo and coleoptile growth in the first few days of germination. At least four α-amylase isoforms have been described in wheat grain but only a subset of specific isoforms are involved either in grain development or in the germination process (Mieog et al, 2017)
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