Physiological and genetic aspects of a diploid potato population in the Netherlands and Northern Finland

Tuberization of potatoes exposed to different photoperiod regimes has been earlier investigated in several studies. However, there is still a limited understanding of the entire tuberization process and the factors influencing this process. One of the constraints of the previous studies has been the use of only one or a few genotypes. Furthermore, the experimental designs have not utilised the natural growing conditions with continuous changes in daylength during the growing season. The general aim of the project was to study the developmental dynamics of the broad-based potato (Solanum tuberosum L.) (CxE) population development at different climatical regimes under the very long-day, long-day and short conditions in Finland, the Netherlands and Ecuador/Venezuela, respectively. In this paper we are presenting some of the results achieved in the studies in Finland during the growing season 2004. In addition to population level trait characteristics we also describe here some of the identified QTLs (quantitative trait loci) for stolon related and tuber formation traits. In some cases we also compare the expression of some of the traits both in Finland and Netherlands.The main difference between the CxE population grown in Finland and the Netherlands was that the onset of flowering took place one week later in Finland. The relationship between tuber initiation and onset of flowering differed depending on the day length. In Finland approximately 70 % of the genotypes had swollen stolon tips before the onset of flowering, while in the Netherlands only 30 % of the genotypes had reached this condition. We also found numerous different trait linked QTLs, for example, a QTL associated with tuber formation was identified on chromosome E5, and QTLs associated with stolon characteristics on chromosomes E1, E4, E10 and E12. As a conclusion, the present preliminary results provide a good basis for determining the influence of different environmental conditions on potato development. In addition, the QTLs obtained in this study give a better understanding of the genetics of complex characters, and can be used in improving the potato crop in breeding programs

Unravelling enzymatic discoloration in potato through a combined approach of candidate genes, QTL, and expression analysis

Enzymatic discoloration (ED) of potato tubers was investigated in an attempt to unravel the underlying genetic factors. Both enzyme and substrate concentration have been reported to influence the degree of discoloration and as such this trait can be regarded as polygenic. The diploid mapping population C × E, consisting of 249 individuals, was assayed for the degree of ED and levels of chlorogenic acid and tyrosine. Using this data, Quantitative Trait Locus (QTL) analysis was performed. Three QTLs for ED have been found on parental chromosomes C3, C8, E1, and E8. For chlorogenic acid a QTL has been identified on C2 and for tyrosine levels, a QTL has been detected on C8. None of the QTLs overlap, indicating the absence of genetic correlations between these components underlying ED, in contrast to earlier reports in literature. An obvious candidate gene for the QTL for ED on Chromosome 8 is polyphenol oxidase (PPO), which was previously mapped on chromosome 8. With gene-specific primers for PPO gene POT32 a CAPS marker was developed. Three different alleles (POT32-1, -2, and -3) could be discriminated. The segregating POT32 alleles were used to map the POT32 CAPS marker and QTL analysis was redone, showing that POT32 coincides with the QTL peak. A clear correlation between allele combinations and degree of discoloration was observed. In addition, analysis of POT32 gene expression in a subset of genotypes indicated a correlation between the level of gene expression and allele composition. On average, genotypes having two copies of allele 1 had both the highest degree of discoloration as well as the highest level of POT32 gene expression

Targeted transcript mapping for agronomic traits in potato

A combination of cDNA-amplified fragment length polymorphism (AFLP) and bulked segregant analysis (BSA) was used to identify genes co-segregating with earliness of tuberization in a diploid potato population. This approach identified 37 transcript-derived fragments with a polymorphic segregation pattern between early and late tuberizing bulks. Most of the identified transcripts mapped to chromosomes 5 (19 markers) and 12 (eight markers) of the paternal map. Quantitative trait locus (QTL) mapping of tuberization time also identified earliness QTLs on these two chromosomes. A potato bacterial artificial chromosome (BAC) library was screened with four of the markers linked to the main QTL. BAC contigs containing the markers showing the highest association with the trait have been identified. One of these contigs has been anchored to chromosome 5 on an ultradense genetic map of potato, which could be used as a starting point for map-based cloning of genes associated with earliness

Physiological and genetical aspects of the broad based potato population (Solanum tuberosum L.) in the Netherlands and Northern Finland

Sisältö: CD-ROM sisältää artikkelit Maatalouspäivien 2006 esitelmistä ja postereista kokonaisuudessaan.vokBEL/SB