Cytogenetic analysis of meiotic behaviour and stability in a trigeneric hybrid (triticale x trigopiro)

Abstract

Trigeneric hybrids in Triticeae may help to establish evolutionary relationships amongdifferent genomes present in the same cellular-genetic background and to transferdifferent alien characters into cultivated wheat. In the present study, a trigeneric hybridinvolving species of Triticum, Secale, and Thinopyrum was synthesized by crossinghexaploid triticale with hexaploid trigopiro. The meiotic behaviour of chromosomesbelonging to different genomes was analyzed, using classical and in situ hybridizationtechniques in F1, F2, and F3 generations of the trigeneric hybrid. The purpose of thisstudy was to determine the chromosome number and genomic constitution and todiscuss the mechanisms involved in the stabilization of the artificial tricepiro hybrids.The chromosome number of the trigeneric F1 hybrid was 2n=42. Between 12 and 16bivalents were observed in the central zone of the equatorial meiotic plate andbetween 9 and 18 univalents were found in the periphery of the MI equatorial plate.Seven of these univalents showed hybridization signals with rye DNA. Lagging rye andnon-rye chromosomes and separation of sister chromatids were found in anaphase I.Tetrads with a maximum of six micronuclei, with and without hybridization signals ofrye DNA, were observed. After three generations, meiotic cells revealed the presenceof 42 chromosomes and 21 bivalents in diakinesis cells. The presence of 14 ryechromosomes and the complete pairing of chromosomes in F3 hybrids suggest thatrye chromosomes would be preferentially transmitted to the progeny and that anelimination mechanism would act on chromosomes of Thinopyrum and wheat Dgenome.