title: Association genetics in Solanum tuberosum provides new insights into potato tuber bruising and enzymatic tissue discoloration.
abstract: BACKGROUND
  Most 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany. urbany@mpipz.mpg.de
authors.forename: Claude
authors.initials: C
authors.lastname: Urbany
authors.forename: Benjamin
authors.initials: B
authors.lastname: Stich
authors.forename: Lysann
authors.initials: L
authors.lastname: Schmidt
authors.forename: Ludwig
authors.initials: L
authors.lastname: Simon
authors.forename: Hergen
authors.initials: H
authors.lastname: Berding
authors.forename: Holger
authors.initials: H
authors.lastname: Junghans
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Niehoff
authors.forename: Alexander
authors.initials: A
authors.lastname: Braun
authors.forename: Eckhard
authors.initials: E
authors.lastname: Tacke
authors.forename: Hans-Rheinhardt
authors.initials: HR
authors.lastname: Hofferbert
authors.forename: Jens
authors.initials: J
authors.lastname: Lübeck
authors.forename: Josef
authors.initials: J
authors.lastname: Strahwald
authors.forename: Christiane
authors.initials: C
authors.lastname: Gebhardt
mesh_terms: D005519:Food Preservation; D010641:Phenotype; D035281:Plant Tubers / Q000201:enzymology / Q000235:genetics*; D011110:Polymorphism, Genetic; D011198:Solanum tuberosum / Q000201:enzymology / Q000235:genetics*