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Wheat Information Service
Number 83: 35-46 (1996)

III. Compendium

A compendium of reciprocal translocations in wheat: 2nd Edition

R. Schlegel

Institute of Wheat and Sunflower Research, BG-9520 General Toshevo/Dobrich, Bulgaria


Summary

Wheat varieties and wheat species are frequently differentiated by reciprocal translocations of inhomologous chromosomes. Therefore, for several studies the knowledge about interchanges is required. A list was compiled summarizing available data on the presence and number of translocations, on configurations observed and their frequencies of occurrence and on involved chromosomes from 466 wheat combinations. The modified chromosomes are usually identified after common chromosome studies, intercrossing and meiotic analysis in F₁ hybrids. Among the wheat accessions listed 19.7% show a non- translocated karyotype, while the remaining show multivalent configurations of types 1⁴ (51.3%),2⁴ (20.4%), 3⁴(3.4%), 4⁴ (0.6%), 1⁶(1.7%), 1⁸(0.4%), 1⁴+1⁶ (1.7%) and 2⁴+1⁶ (1.6%). The chromosomes 1A, 7B and 2D are most frequently associated with translocations. Between the genomes the B genome exhibits the most interchanges (A=12.3%, B=61.4%, D=26.3%). However, no close correlations were evident between individual chromosome length (mu m), 4C DNA content per chromosome (pg) and the frequency of chromosome involved in translocations (r=<0.4**).


Introduction

Wheat varieties are often differentiated by structural changes of the genome such as reciprocal translocations, deletions, inversions, duplications or heterochromatin polymorphisms. The translocations are mostly identified after crossing analysis and karyological studies. Critical F₁ hybrids show multivalent interchange configurations with different frequencies per pollen mother cell. Meanwhile, there are quite a number of cultivars in wheat characterized by the presence of reciprocal translocations and/or their absence. For monosomic analysis, chromosome identification, identity proof of a variety and for several other reasons the knowledge on interchanges is required. Therefore, a second compilation was prepared summarizing available data on the presence and number of translocations, on configurations and chromosomes involved in the interchanges as well as on the origin of the material.

The nomenclature for types of translocated chromosomes follows recommendation of Koebner and Miller (13). The origin of release of the variety/strain is included in the inventory. The pairs of critical varieties were alphabetically arranged, according to the number of translocations found in the material. Although in some combinations several types of interchanges were found possibly introduced by different genotypes / karyotypes of the populations, they all were considered but separated by a comma. Hybrids with more than one interchange in a given hybrid are characterized by the types of association connected with a plus sign(+). 1⁴ designates one quadrivalent present in the hybrid, 1⁶=one hexavalent, l⁸=one octovalent, 2⁴=two quadrivalents, 1⁴+ l⁶=one quadrivalent plus one hexavalent, etc. The chromosomes 4A and 4B are considered after the new nomenclature of wheat chromosomes.

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