A Semi-micro Assay and Genetic Analysis for Late-maturity Alpha-amylase Activity in Bread Wheat

Pre-harvest sprouting (PHS) in cereal crops is generally associated with high levels of late-maturity aplha-amylase activity (LMAA). Alpha-amylase is one of the enzymes that occurs naturally in all wheat (Triticum aestivum L.) and is activated during the germination or sprouting process. Its activity can quickly break down starch and convert into free sugar molecules, resulting in reduced end-products quality. A semi-micro assay procedure was developed to quantify LMAA in spring wheat. The assay enables a single individual realistically to screen at least 120 samples each day and it is therefore suitable for use in a high-throughput breeding program. This proposed alternative to prior assays of LMAA uses at least two-third fewer reagents, as a result, it costs approximately $1 USD/data point. An international collection (IC) of eighteen spring wheat genotypes and a separate set of fifteen spring wheat cultivars adapted to South Dakota (SD) were evaluated for LMAA over five and thirteen site-year environments, respectively. A GGE model and a mixed linear model approach MINQUE were used to analyse the datasets. Broad-sense heritability for LMAA was higher among cultivars adapted to SD (53%) when compared to the IC genotypes (49%). Significant genetic effects predicted genotypes, such as, ‘Lancer’, ‘Chester’ and ‘LoSprout’ from IC, as well as ‘Alsen’ and ‘Forefront’ from SD could best be used as parents to develop PHS resistant genotypes with low levels of LMAA. Stability analysis using an AMMI bi-plot exhibited that Chester, Lancer and ‘Advance’ were the most stable across environments. A crossing population was developed by hybridizing parents with high- and with low levels of LMAA. The parents and their progeny in the F2 and in F3 generations were evaluated for LMAA. Datasets were analysed using the R software package ‘qgtools_1.0’ integrated with an additive-dominance genetic model and a MINQUE approach. The narrow-sense heritability for LMAA was found to be 12%. Significant negative additive effects for parents revealed that ‘Lancer’ and ‘Chester’ are good general combiners, and significant negative dominance effects and best-parent heterosis for hybrids showed specific hybrid combinations, such as, ‘Chester’/‘Kinsman’, ‘Lerma52’/‘Lancer’, ‘Lerma52’/‘LoSprout’ and ‘Janz’/‘Seri-82’ would produce progeny with low expression of LMAA