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B chromosomes: a physiological enigma

Published online by Cambridge University Press:  01 September 1997

SUSAN M. BOUGOURD  and
R. NEIL JONES
SUSAN M. BOUGOURD
Affiliation:
Department of Biology, University of York, York YO1 5DD, UK
R. NEIL JONES
Affiliation:
Institute of Biological Sciences, University of Wales Aberystwyth, Aberystwyth SY23 3DD, UK
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Abstract

The concept of the ‘nucleotype’ embraces aspects of the nuclear DNA that affect the phenotype other than through the coding sequences. In this context, we consider one particular situation, namely DNA variation due to the presence of supernumerary B chromosomes (Bs); these Bs, which are additional to the basic complement of A chromosomes, generate a spectrum of DNA amounts, and thus nucleotypes, within many species. We consider the physiological consequences of carrying extra chromosomes that appear by and large to lack coding sequences, and focus on two species with contrasting case histories: rye (Secale cereale L.) and chives (Allium schoenoprasum L.), which illustrate ‘selfish’ and ‘adaptive’ explanations of the persistence of B chromosomes.

Keywords

Allium schoenoprasum L. (chives)B chromosomesnucleotypeSecale cereale L. (rye)stress tolerance
Type
Research Article
Information
The New Phytologist , Volume 137 , Issue 1 , September 1997 , pp. 43 - 54
Copyright
© Trustees of the New Phytologist 1997

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