Abstract
Tuber yield, starch content, starch yield and chip color are complex traits that are important for industrial uses and food processing of potato. Chip color depends on the quantity of reducing sugars glucose and fructose in the tubers, which are generated by starch degradation. Reducing sugars accumulate when tubers are stored at low temperatures. Early and efficient selection of cultivars with superior yield, starch yield and chip color is hampered by the fact that reliable phenotypic selection requires multiple year and location trials. Application of DNA-based markers early in the breeding cycle, which are diagnostic for superior alleles of genes that control natural variation of tuber quality, will reduce the number of clones to be evaluated in field trials. Association mapping using genes functional in carbohydrate metabolism as markers has discovered alleles of invertases and starch phosphorylases that are associated with tuber quality traits. Here, we report on new DNA variants at loci encoding ADP-glucose pyrophosphorylase and the invertase Pain-1, which are associated with positive or negative effect with chip color, tuber starch content and starch yield. Marker-assisted selection (MAS) and marker validation were performed in tetraploid breeding populations, using various combinations of 11 allele-specific markers associated with tuber quality traits. To facilitate MAS, user-friendly PCR assays were developed for specific candidate gene alleles. In a multi-parental population of advanced breeding clones, genotypes were selected for having different combinations of five positive and the corresponding negative marker alleles. Genotypes combining five positive marker alleles performed on average better than genotypes with four negative alleles and one positive allele. When tested individually, seven of eight markers showed an effect on at least one quality trait. The direction of effect was as expected. Combinations of two to three marker alleles were identified that significantly improved average chip quality after cold storage and tuber starch content. In F1 progeny of a single-cross combination, MAS with six markers did not give the expected result. Reasons and implications for MAS in potato are discussed.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-2035-z) contains supplementary material, which is available to authorized users.
Highlights
Potatoes are grown worldwide for food, feed and industrial uses
Chip color depends on the quantity of reducing sugars glucose and fructose in the tubers, which are generated by starch degradation
The amount of reducing sugars increases when tubers are stored at temperatures below 10 °C, which are preferred by the industry to inhibit sprouting and to extend marketability
Summary
Potatoes are grown worldwide for food, feed and industrial uses. The tubers are the source of carbohydrates, high quality protein, essential vitamins, minerals and trace elements. A further important quality criterion arises from the requirements of the food processing industry, which produces chips, French fries and other deep fried products from potatoes This criterion is the tuber content of the reducing sugars fructose and glucose, which determines the culinary quality of chips and French fries (Brown et al 1990; Hayes and Thill 2002; Kirkman 2007; Mackay et al 1990; Xiong et al 2002). The amount of reducing sugars increases when tubers are stored at temperatures below 10 °C, which are preferred by the industry to inhibit sprouting and to extend marketability. This cold-induced sweetening is an adaptive response to osmotic stress (Sowokinos 2001). Tuber starch and sugar content are, connected and part of the same metabolic network
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