“x” is not a bias, but a number with real biological significance

Abstract

Recent literature criticized the use of the symbol “x” to denote basic chromosome number in cytotaxonomy. I show here that this criticism is superfluous and is based on historical confusion between the concepts of basic chromosome number (or monoploid chromosome number), which is objective, and ancestral basic chromosome number, which is always inferred, by means of several – more or less reliable – methods. The most relevant literature is discussed and, in the end, I propose the use of x for basic chromosome number and p for (hypothetical) ancestral basic chromosome number.

Keywords::

• Chromosome number
• cytology
• cytotaxonomy
• basic chromosome number
• base number

Acknowledgements

The author wishes to thank Carlo Blasi, Editor-in-Chief of Plant Biosystems, for his interest and support for this initiative.

Additional information

Funding

Financial funding (EX60%) from University of Pisa is gratefully acknowledged.