Genome-wide association study of lipase and esterase in wholegrain wheat flour (Triticum aestivum L.)

Abstract

Lipase activity is one of the main causes of the lipid rancidity in wholegrain wheat flour, leading to its short shelf life. Genetically diverse wheat germplasm offers potential for the selection of wheat cultivars with low lipase activity for stable wholegrain end use. This study evaluated 300 European wheat cultivars harvested in 2015 and 2016 on the genetic association of lipase and esterase activities in wholegrain wheat flour. Esterase and lipase activities in wholegrain flour were measured photometrically with p-nitrophenyl butyrate and p-nitrophenyl palmitate as substrates, respectively. Both enzyme activities showed wide ranges among all cultivars within each year, with differences up to 2.5-fold. The two years showed low correlations between each other, indicating a large environmental impact on the enzyme activities. Cultivars 'Julius' and 'Bueno' were suggested to be better suited for stable wholegrain products, as they had consistently low esterase and lipase activities compared to the other cultivars. A genome-wide association study revealed associations with single nucleotide polymorphisms in genes located on the high-quality wheat genome sequence of the International Wheat Genome Sequencing Consortium. Eight and four candidate genes were tentatively proposed to be associated to esterase and lipase activity, respectively, in wholegrain flour. Our work shows esterase and lipase activities from a new perspective, that combines reverse genetics to understand the underlying causes. This study outlines the possibilities and limitations to improve lipid stability of wholegrain wheat by genomics-assisted breeding methods, thereby offering new opportunities to optimize the quality of wholegrain wheat flour and wholegrain products.

Fig 1

Esterase (A) and lipase (B) activities of 300 wheat cultivars grown in 2015 and 2016. Each dot and number represent one wheat cultivar. Linear regression model of esterase activity from the two years is represented by the blue line. Cultivars with their esterase (C) and lipase (D) activities in the upper and lower quantiles in both years. Cultivars overlapped in (C) and (D) were labeled in orange.

Fig 2

Manhattan plots for esterase (A, C) and lipase (B, D) activity of the GABI-panel harvested in 2015 (A, B) and 2016 (C, D). The x-axis shows the relative position across 7 chromosomes and the y-axis the -log₁₀P-value. The three genomes, A, B and D, are represented by black, orange and blue, respectively. Significant line is drawn at FDR p = 0.02.