Wheat–barley hybrids and introgression lines

Bread wheat Triticum aestivum L. and barley Hordeum vulgare L. are two of the most important cultivated cereals worldwide. Barley has several agronomic characters (e.g. earliness, tolerance to drought or soil salinity, various quality parameters) which it would be desirable to transfer into wheat. The first step in alien gene transfer via chromosome manipulation is the production of interspecific or intergeneric hybrids. One of the major limitations for successful gene transfer from barley into wheat is the low crossability between these species. Successful hybridizations and the production of barley introgressions have taken place over the last few decades, making it possible to overcome some of the difficulties. An overview is given here of wheat × barley hybridizations using Hordeum vulgare L. and other Hordeum species, including the development of hybrids and introgressions with various barley cultivars. The meiotic pairing behaviour of hybrids is presented, with special emphasis on the monitoring of wheat–barley homoeologous pairing by means of molecular cytogenetic methods. The effect of in vitro multiplication on the genome composition of intergeneric hybrids is discussed, and the agronomical traits (β-glucan content, earliness, salt tolerance, etc.) of the newly developed introgression lines are presented. The exploitation and possible use of wheat/barley introgression lines in the most up-to-date molecular genetic studies (transcriptome analysis, sequencing of flow-sorted chromosomes) are also discussed.