The Range of Chromosomal Variations in Intergeneric Hybrids Involving Some Triticeae

Abstract

Chromosomal variations in intergeneric hybrids among the Triticeae occur consistently and at various phases in the formation and the ontogeny of the hybrid. To a certain extent the events are fortuitous but in other situations the variation may pose a serious constraint in alien genetic transfer programs. Stable amphiplopids are a prerequisite for the development of alien chromosome addition lines and the production of disomic alien chromosome additions could be considerably thwarted if stable amphiploids are not available. This constraint forces the adoption of a methodology where the F₁ self-sterile hybrid is utilized to generate F₁ backcross I (BC₁) progeny. The derivatives are generally stable but do possess the potential of yielding alien structural chromosomal modifications. Cytogenetic screening of large amphiploid and BC1 populations has yielded stable, expected normal plants with high seed fertility. Genomic elimination has also been identified in a low frequency. In the applied alien gene transfer however, chromosomal variations have a decided breeding advantage, particularly for the complex polygenically controlled characters. The occurrence of chromosomal variations is a novel means of augmenting those associated with callus culture and induced mutagenesis. This paper reviews our progress as it elucidates the chromosomal variability in various aspects of intergeneric hybrid production, development, and maintenance of the derived genetic stocks.