AUTHOR=Carpenter Margaret A. , Joyce Nigel I. , Genet Russell A. , Cooper Rebecca D. , Murray Sarah R. , Noble Alasdair D. , Butler Ruth C. , Timmerman-Vaughan Gail M. 

TITLE=Starch phosphorylation in potato tubers is influenced by allelic variation in the genes encoding glucan water dikinase, starch branching enzymes I and II, and starch synthase III

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00143

DOI=10.3389/fpls.2015.00143

ISSN=1664-462X

ABSTRACT=<p>Starch phosphorylation is an important aspect of plant metabolism due to its role in starch degradation. Moreover, the degree of phosphorylation of starch determines its physicochemical properties and is therefore relevant for industrial uses of starch. Currently, starch is chemically phosphorylated to increase viscosity and paste stability. Potato cultivars with elevated starch phosphorylation would make this process unnecessary, thereby bestowing economic and environmental benefits. Starch phosphorylation is a complex trait which has been previously shown by antisense gene repression to be influenced by a number of genes including those involved in starch synthesis and degradation. We have used an association mapping approach to discover genetic markers associated with the degree of starch phosphorylation. A diverse collection of 193 potato lines was grown in replicated field trials, and the levels of starch phosphorylation at the C6 and C3 positions of the glucosyl residues were determined by mass spectrometry of hydrolyzed starch from tubers. In addition, the potato lines were genotyped by amplicon sequencing and microsatellite analysis, focusing on candidate genes known to be involved in starch synthesis. As potato is an autotetraploid, genotyping included determination of allele dosage. Significant associations (<italic>p</italic> &lt; 0.001) were found with SNPs in the glucan water dikinase (<italic>GWD</italic>), starch branching enzyme I (<italic>SBEI</italic>) and the starch synthase III (<italic>SSIII</italic>) genes, and with a SSR allele in the <italic>SBEII</italic> gene. SNPs in the <italic>GWD</italic> gene were associated with C6 phosphorylation, whereas polymorphisms in the <italic>SBEI</italic> and <italic>SBEII</italic> genes were associated with both C6 and C3 phosphorylation and the SNP in the <italic>SSIII</italic> gene was associated with C3 phosphorylation. These allelic variants have potential as genetic markers for starch phosphorylation in potato.</p>