The inheritance of genetic variation in Triticum speltoides affecting heterogenetic chromosome pairing in hybrids with Triticum aestivum

Abstract

Triticum speltoides (Tausch) Gren. ex Richter plants which differed in the ability to promote heterogenetic chromosome pairing in hybrids T. aestivum L. × T. speltoides were crossed and a single F1 plant from each cross was hybridized with T. aestivum. The segregation among the hybrids for mean number of chiasmata per cell showed that two gene systems in T. speltoides genotypes were involved in the promotion of heterogenetic pairing. One system was composed of two duplicate gene loci segregating independently of each other. Variation at these loci determined two basic levels of heterogenetic pairing. The other system was composed of several minor genes extensively modifying the effects of the major genes. The minor genes interacted mostly in an additive fashion. Triticum speltoides inbred plants were then crossed with diploid species. T. tauschii (Coss.) Schmal and T. dichasians (Zhuk.) Bowden. Consistent differences in the levels of chromosome pairing were found in these hybrids. However, this variation in chromosome pairing did not coincide with the variation at the major gene loci. This indicated that the major genes were ineffective in the diploid hybrids.Key words: Triticum, pairing regulation, homeologous pairing, heterogenetic pairing.