Abstract
Potato (Solanum tuberosum L.) tubers exhibit significant variation in reducing sugar content directly after harvest, cold storage and reconditioning. Here, we performed QTL analysis for chip color, which is strongly influenced by reducing sugar content, in a diploid potato mapping population. Two QTL on chromosomes I and VI were detected for chip color after harvest and reconditioning. Only one region on chromosome VI was linked with cold-induced sweetening. Using the RT-PCR technique, we showed differential expression of the auxin-regulated protein (AuxRP) gene. The AuxRP transcript was presented in light chip color parental clone DG 97-952 and the RNA progeny of the bulk sample consisting of light chip color phenotypes after cold storage. This amplicon was absent in dark chip parental clone DG 08-26/39 and the RNA bulk sample of dark chip progeny. Genetic variation of AuxRP explained up to 16.6 and 15.2 % of the phenotypic variance after harvest and 3 months of storage at 4 °C, respectively. Using an alternative approach, the RDA-cDNA method was used to recognize 25 gene sequences, of which 11 could be assigned to potato chromosome VI. One of these genes, Heat-shock protein 90 (Hsp90), demonstrated higher mRNA and protein expression in RT-qPCR and western blotting assays in the dark chip color progeny bulk sample compared with the light chip color progeny bulk sample. Our study, for the first time, suggests that the AuxRP and Hsp90 genes are novel candidate genes capable of influencing the chip color of potato tubers.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-015-0415-1) contains supplementary material, which is available to authorized users.
Highlights
Glucose and fructose are osmotically active substances that protect plants during low temperature stress or act as cryoprotectants during frosts (Stitt and Hurry 2002)
Chip color measured after harvest (AH), cold storage (CS) and reconditioning (RC) in the parents DG 97-952 and DG 08-26/39 was 8.5 and 4.5; 7.0 and 4.0; 6.7 and 5.3, respectively
The number of genotypes with chip color 1–3 increased during reconditioning at °C (RC) (8 % of genotypes became darker after RC compared with CS)
Summary
Glucose and fructose are osmotically active substances that protect plants during low temperature stress or act as cryoprotectants during frosts (Stitt and Hurry 2002). In potato (Solanum tuberosum L.) tubers, 224 Page 2 of 12 the content of the reducing sugars immediately after harvest is generally low. Sugar accumulates as a result of starch breakdown (Sonnewald and Kossmann 2013). This process depends on the genotype and reflects the environmental conditions of plant growth, the harvest date and the storage regimen (Tai and Coleman 1999; Jakuczun and Zimnoch-Guzowska 2004). Sucrose can be transported into vacuoles or broken down into glucose and fructose This phenomenon is known as cold-induced sweetening (CIS) (Isherwood 1973) and protects the plants from cold stress but is unacceptable to consumers. Low level of reducing sugars in potato tubers is one of the most important requirements in their processing worldwide
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