title: Diversity and dynamics of plant genome size: an example of polysomaty from a cytogenetic study of Tahitian vanilla (Vanilla xtahitensis, Orchidaceae).
abstract: OBJECTIVE
  Abnormal mitotic behavior with somatic aneuploidy and partial endoreplication were previously reported for the first time in the plant kingdom in Vanilla planifolia. Because vanilla plants are vegetatively propagated, such abnormalities have been transmitted. This study aimed to determine whether mitotic abnormalities also occur in Vanilla hybrid or are suppressed by sexual reproduction.
  
  
  METHODS
  Twenty-eight accessions of Vanilla ×tahitensis, one V. planifolia, and hybrid V. planifolia × V. ×tahitensis were analyzed by chromosome counts, cytometry, and fluorescent in situ hybridization of 18S-5.8S-26S rDNA.
  
  
  RESULTS
  In a single root meristem of V. ×tahitensis, chromosome number varied from 22 to 31 in diploids (mean 2C = 5.23 pg), 31 to 41 in triploids (2C = 7.82 pg) and 43 to 60 in tetraploids (2C = 10.27 pg). Morphological diversity is apparently related to ploidy changes. Aneuploidy and partial (asymmetrical) endoreduplication were observed in root meristems of both V. ×tahitensis and the hybrid V. planifolia × V. ×tahitensis, but pollen grains had the euploid chromosome number (n = 15 in diploids).
  
  
  CONCLUSIONS
  Genome irregularities may be transmitted not only during vegetative propagation but also by sexual reproduction in Vanilla. However, there must be a complex regulation of genome size and organization between the aneuploidy in somatic tissues and subsequently euploid gametic tissue. This is a novel example of polysomaty with developmentally regulated partial endoreplication.
authors: Etablissement Vanille de Tahiti, Département Recherche et Développement, BP 40135 Fare Tony 98713 Papeete, French Polynesia. sandra.andrzejewski@labo-vanilledetahiti.pf
authors: Sandra
authors: S
authors: Lepers-Andrzejewski
authors: Sonja
authors: S
authors: Siljak-Yakovlev
authors: Spencer C
authors: SC
authors: Brown
authors: Maurice
authors: M
authors: Wong
authors: Michel
authors: M
authors: Dron