GENETIC MECHANISMS OF LATE-MATURITY ALPHA-AMYLASE IN SPRING AND WINTER WHEAT (TRITICUM AESTIVUM L.) UNDER DISCRETE AND CONTINUOUS TEMPERATURE STRESS
Creators: name: Marston, Elliott J.
Publisher: name: Washington State University
Year: 2024
Subjects: Falling number
Late-maturity alpha-amylase
wheat
wheat quality
Plant pathology

description: Wheat (Triticum aestivum L.) quality is a priority for both wheat growers and breeders in Washington state where 85%-95% of wheat is exported. Multiple metrics are used to determine wheat quality and price, including the Falling Number (FN) test. The FN test assesses starch integrity and estimates end-use quality by indirectly measuring α-amylase activity in a representative grain sample. High α-amylase levels result in a low FN and are associated with poor end-use outcomes; growers are financially penalized for FN scores below the industry standard of 300s. Low FN scores have traditionally been attributed to Pre-harvest sprouting (PHS) where grain germinates on the mother plant prior to harvest under conducive weather conditions. As of 2016, late-maturity α-amylase (LMA) has been identified as an additional source of low FN in Washington state. Researchers have identified multiple major quantitative trait loci (QTL) that confer tolerance to constitutive LMA expression or suppress LMA under warm temperatures. The full genetic mechanisms of LMA have yet to be characterized and no major QTL associated with LMA tolerance in the presence of GA-insensitive dwarfing alleles have been published at this time. The goal of this study was to identify QTL associated with LMA tolerance under discrete and continuous cold conditions in both winter and spring wheat.
description: We also aimed to determine the effect of GA-insensitive reduced height (Rht) alleles Rht-B1b and Rht-D1b on LMA expression. Spring wheat was assessed for association of LMA-expression with other abiotic stress tolerance traits, including grain fill, tiller number, anthocyanin expression, and spike distortion. A biparental winter wheat mapping population was used to assess LMA-expression under discrete cold stress in field grown material. A nested association mapping (NAM) population of ten closely related subpopulation was utilized to assess LMA-expression in spring wheat under both discrete and continuous cold stress conditions in greenhouse grown material. We genotyped both the biparental and NAM populations using genotyping-by-sequencing (GBS) methods for generating single nucleotide polymorphism (SNP) markers that were used to construct linkage maps and perform QTL mapping. At least one major QTL was mapped to each chromosome by a biparental population or NAM subpopulation. We found that GA-insensitive Rht alleles had environmentally specific effects and failed to suppress LMA under cold temperatures. QTL also displayed strong environment specific effects with little overlap, suggesting that genetic mechanisms of LMA expression are temperature dependent. Putative gene searches within QTL intervals identified annotated genes associated with biotic and abiotic stress signaling pathways, cellular respiration, and osmotic homeostasis. We also identified a positive correlation between LMA expression and abiotic stress tolerance, particularly cold stress traits. Evidence from this study reveals that LMA associated with temperature stress is a tissue specific cold tolerance mechanism of developing grain. Future studies on LMA should focus on environment specific genetic control. Further characterization of the abiotic stress signaling pathways associated with LMA expression are required as this study implies that breeding for LMA tolerance may reduce overall abiotic stress tolerance.