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

ABSTRACT: 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 x 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.

SUBMITTER: Werij JS

PROVIDER: S-EPMC1913181 | biostudies-literature | 2007 Jul

REPOSITORIES: biostudies-literature

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

Werij Jeroen S JS Kloosterman Bjorn B Celis-Gamboa Carolina C de Vos C H Ric CH America Twan T Visser Richard G F RG Bachem Christian W B CW

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik 20070511 2

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 x 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 QT ...[more]

PMID: 17492422

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Project description:Tuber tissue discolorations caused by impact (blackspot bruising) and enzymatic discoloration (ED) after tuber cutting are crucial quality traits of the cultivated potato. To understand the complex genetics of the traits, quantitative trait locus (QTL) analysis using diploid mapping population and diversity array technology (DArT) markers was performed. The phenotypic assessment included the complex evaluation of blackspot bruising susceptibility through two methods: rotating drum (B RD) and falling bolt (B FB) in combination with the evaluation of enzymatic discoloration. Because of observed in-practice relationship between bruising susceptibility and tuber starch content (TSC), analysis of starch content-corrected bruising susceptibility (SCB) was performed. QTLs for bruising were detected on chromosomes I, V with both test methods. The rotating drum method enabled the detection of additional QTLs on chromosomes VIII and XII. Analysis of SCB enabled the identification of the major QTL on chromosome V and two weaker QTLs on chromosomes VIII and XII, independently of starch content. The QTL for bruising detected on chromosome I overlapped with the most significant QTL for tuber starch content. This QTL was not significant for starch content-corrected bruising susceptibility, and the effect of the QTL on chromosome V was enhanced for this trait. The QTL analysis of ED revealed the contribution of seven QTLs for the trait, located on six chromosomes, including these detected for the first time: a major locus on chromosome V and minor QTLs on chromosomes VII and X, which were specific for the trait. The QTL for ED on chromosome VIII was co-localized with the marker for polyphenol oxidase (POT32). The phenotypic correlation between bruising and ED was confirmed in QTL analyses of both traits, and the QTLs detected for these traits overlapped on chromosomes I, V, and VIII. Our results should provide a basis for further studies on candidate genes affecting blackspot bruise susceptibility and enzymatic discoloration.

Project description:BackgroundMost agronomic plant traits result from complex molecular networks involving multiple genes and from environmental factors. One such trait is the enzymatic discoloration of fruit and tuber tissues initiated by mechanical impact (bruising). Tuber susceptibility to bruising is a complex trait of the cultivated potato (Solanum tuberosum) that is crucial for crop quality. As phenotypic evaluation of bruising is cumbersome, the application of diagnostic molecular markers would empower the selection of low bruising potato varieties. The genetic factors and molecular networks underlying enzymatic tissue discoloration are sparsely known. Hitherto there is no association study dealing with tuber bruising and diagnostic markers for enzymatic discoloration are rare.ResultsThe natural genetic diversity for bruising susceptibility was evaluated in elite middle European potato germplasm in order to elucidate its molecular basis. Association genetics using a candidate gene approach identified allelic variants in genes that function in tuber bruising and enzymatic browning. Two hundred and five tetraploid potato varieties and breeding clones related by descent were evaluated for two years in six environments for tuber bruising susceptibility, specific gravity, yield, shape and plant maturity. Correlations were found between different traits. In total 362 polymorphic DNA fragments, derived from 33 candidate genes and 29 SSR loci, were scored in the population and tested for association with the traits using a mixed model approach, which takes into account population structure and kinship. Twenty one highly significant (p < 0.001) and robust marker-trait associations were identified.ConclusionsThe observed trait correlations and associated marker fragments provide new insight in the molecular basis of bruising susceptibility and its natural variation. The markers diagnostic for increased or decreased bruising susceptibility will facilitate the combination of superior alleles in breeding programs. In addition, this study presents novel candidates that might control enzymatic tissue discoloration and tuber bruising. Their validation and characterization will increase the knowledge about the underlying biological processes.

Dataset Information

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

Publications

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

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