The Hordeum bulbosum (L.) method

Abstract

The development of superior barley cultivars has been a continuing dynamic breeding process for many different characters. Being primarily self-pollinated, barley landraces and modern cultivars have been mostly homozygous and several methods of breeding including pedigree, bulk, backcross, single-seed descent have been successful for many years. The newest and most important development in breeding methods of barley has been the recovery of high frequencies of doubled haploids (DH) i.e. homozygous lines in a single generation. Several methods are available for DH production in barley. The first to be reported in the early 1970s was the interspecific hybridization of cultivated barley (Hordeum vulgare L.) with H. bulbosum L. (Kasha and Kao, 1970). Haploid plantlets of H. vulgare are generated as a result of gradual elimination of H. bulbosum chromosomes from hybrid embryos between the two species. Scientists and breeders rapidly adopted the method because DH provide several advantages over standard selection and breeding methods. This chapter describes a protocol for the interspecific hybridization of H. vulgare with H. bulbosum, also called the H. bulbosum method that has been used at Florimond Desprez for twenty years to generate DH lines of barley. H. bulbosum. is a perennial outcrossing species found in the Mediterranean region. Although there are two cytotypes, diploid (2n = 2x =14) and tetraploid (2n = 4x = 28), only the diploid form has been used to generate haploid plants of barley.