ABSTRACT Presynaptic alignment occurs at zygotene and early pachytene in a pentaploid hybrid between _Achillea collina_ (4x) and _A. millefolium_ (6x). Mostly, the five corresponding

chromosomes of each set are assorted into a group of three (two synapsed plus one aligned) and a group of two (synapsed); groups of five axes by alignment and/or pairing are extremely rare.

This reflects different degrees of homology between the five genomes and allows inferences about the possible phylogeny and genome formulas of the tetraploid (AASS) and hexaploid (AASSTT)

involved. The alignment as subgroups of three and two chromosomes in their 5x hybrid also indicates that synaptic alignment responds to slightly different degrees of homology and is decisive

two-by-two synapsis. SIMILAR CONTENT BEING VIEWED BY OTHERS VARIETAL VARIATION AND CHROMOSOME BEHAVIOUR DURING MEIOSIS IN _SOLANUM TUBEROSUM_ Article Open access 10 June 2020 MEIOSIS AT

THREE LOCI IN AUTOTETRAPLOIDS: PROBABILITIES OF GAMETE MODES AND GENOTYPES WITHOUT AND WITH PREFERENTIAL CROSS-OVER FORMATION Article 04 February 2023 SCEP1 AND SCEP2 ARE TWO NEW COMPONENTS

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30, 930–939. Article  Google Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Institute of Botany, University of Vienna, Rennweg 14, Wien, A-1030, Austria J Loidl, 

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permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Loidl, J., Ehrendorfer, F. & Schweizer, D. EM analysis of meiotic chromosome pairing in a pentaploid _Achillea_ hybrid. _Heredity_ 65,

11–20 (1990). https://doi.org/10.1038/hdy.1990.64 Download citation * Received: 10 November 1989 * Issue Date: 01 August 1990 * DOI: https://doi.org/10.1038/hdy.1990.64 SHARE THIS ARTICLE

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