Journal Article

Chromosome pairing affinities in interspecific hybrids reflect phylogenetic distances among lady's slipper orchids (<i>Paphiopedilum</i>)

Yung-I Lee, Fang-Chi Chang and Mei-Chu Chung

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 108, issue 1, pages 113-121
Published in print July 2011 | ISSN: 0305-7364
Published online May 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcr114

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Lady's slipper orchids (Paphiopedilum) are of high value in floriculture, and interspecific hybridization has long been used for breeding improved cultivars; however, information regarding the genome affinities of species and chromosome pairing behaviour of the hybrids remains almost unknown. The present work analyses the meiotic behaviour of interspecific hybrids by genomic in situ hybridization and cytologically evaluates the genomic relationships among parental species.

Methods

Eight interspecific F1 hybrids of Paphiopedilum species in various subgenera or sections were investigated in this study. The chromosome behaviour in meiosis of these interspecific hybrids was analysed and subjected to genomic in situ hybridization and fluorescent in situ hybridization.

Key Results

Genomic in situ hybridization was demonstrated as an efficient method to differentiate between Paphiopedilum genomes and to visualize the chromosome pairing affinities in interspecific F1 hybrids, clarifying the phylogenetic distances among these species. Comparatively regular chromosome pairing observed in the hybrids of P. delenatii × P. bellatulum, P. delenatii × P. rothschildianum and P. rothschildianum × P. bellatulum suggested high genomic affinities and close relationships between parents of each hybrid. In contrast, irregular chromosome associations, such as univalents, trivalents and quadrivalents occurred frequently in the hybrids derived from distant parents with divergent karyotypes, such as P. delenatii × P. callosum, P. delenatii × P. glaucophyllum, P. rothschildianum × P. micranthum and P. rothschildianum × P. moquetteanum. The existence of multivalents and autosyndesis demonstrated by genomic in situ hybridization in this study indicates that some micro-rearrangements and other structural alterations may also play a part in differentiating Paphiopedilum species at chromosomal level, demonstrated as different chromosome pairing affinities in interspecific hybrids.

Conclusions

The results indicate that genome homology and the interaction of genetic factors, but not chromosome number nor karyotype similarity, determine the chromosome pairing behaviour in Paphiopedilum hybrids.

Keywords: Paphiopedilum; homeologous pairing; autosyndesis; genomic in situ hybridization; pollen formation

Journal Article.  5138 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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