title: Tuber shape and eye depth variation in a diploid family of Andean potatoes.
abstract: BACKGROUND
  Tuber appearance is highly variable in the Andean cultivated potato germplasm. The diploid backcross mapping population 'DMDD' derived from the recently sequenced genome 'DM' represents a sample of the allelic variation for tuber shape and eye depth present in the Andean landraces. Here we evaluate the utility of morphological descriptors for tuber shape for identification of genetic loci responsible for the shape and eye depth variation.
  
  
  RESULTS
  Subjective morphological descriptors and objective tuber length and width measurements were used for assessment of variation in tuber shape and eye depth. Phenotypic data obtained from three trials and male-female based genetic maps were used for quantitative trait locus (QTL) identification. Seven morphological tuber shapes were identified within the population. A continuous distribution of phenotypes was found using the ratio of tuber length to tuber width and a QTL was identified in the paternal map on chromosome 10. Using toPt-437059, the marker at the peak of this QTL, the seven tuber shapes were classified into two groups: cylindrical and non-cylindrical. In the first group, shapes classified as 'compressed', 'round', 'oblong', and 'long-oblong' mainly carried a marker allele originating from the male parent. The tubers in this group had deeper eyes, for which a strong QTL was found at the same location on chromosome 10 of the paternal map. The non-cylindrical tubers classified as 'obovoid', 'elliptic', and 'elongated' were in the second group, mostly lacking the marker allele originating from the male parent. The main QTL for shape and eye depth were located in the same genomic region as the previously mapped dominant genes for round tuber shape and eye depth. A number of candidate genes underlying the significant QTL markers for tuber shape and eye depth were identified.
  
  
  CONCLUSIONS
  Utilization of a molecular marker at the shape and eye depth QTL enabled the reclassification of the variation in general tuber shape to two main groups. Quantitative measurement of the length and width at different parts of the tuber is recommended to accompany the morphological descriptor classification to correctly capture the shape variation.
authors.affiliation: International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. h.lindqvist-kreuze@cgiar.org.
authors.forename: Hannele
authors.initials: H
authors.lastname: Lindqvist-Kreuze
authors.affiliation: International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. awais.khan@cgiar.org.
authors.forename: Awais
authors.initials: A
authors.lastname: Khan
authors.affiliation: International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. e.salas@cgiar.org.
authors.forename: Elisa
authors.initials: E
authors.lastname: Salas
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch, 8140, New Zealand. mei.meiyalaghan@plantandfood.co.nz.
authors.forename: Sathiyamoorthy
authors.initials: S
authors.lastname: Meiyalaghan
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch, 8140, New Zealand. Susan.Thomson@plantandfood.co.nz.
authors.forename: Susan
authors.initials: S
authors.lastname: Thomson
authors.affiliation: International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. r.gomez@cgiar.org.
authors.forename: Rene
authors.initials: R
authors.lastname: Gomez
authors.affiliation: International Potato Center (CIP), Av. La Molina 1895, Apartado 1558, Lima 12, Peru. m.bonierbale@cgiar.org.
authors.forename: Merideth
authors.initials: M
authors.lastname: Bonierbale
mesh_terms: D002874:Chromosome Mapping; D004171:Diploidy; D017343:Genes, Plant; D056726:Genetic Association Studies; D005819:Genetic Markers; D010641:Phenotype; D035281:Plant Tubers / Q000033:anatomy & histology*; D040641:Quantitative Trait Loci; D019655:Quantitative Trait, Heritable; D011198:Solanum tuberosum / Q000033:anatomy & histology* / Q000235:genetics*
chemical_list: D005819:Genetic Markers