Status of remote hybrids in the Poaceae: problems and prospects

H. Stoyanov
Abstract. Wide hybridization as a tool of classical breeding is a method which is successfully applied in the development of breeding programs in cultural plants. Its application is a particularly effective means to overcome the effects of biotic and abiotic stress in cultural species in Poaceae. Through wide hybridization genes for resistance to phytopathogens, insect pests, tolerance to the toxicity of aluminum, copper, cadmium are successfully transferred. The method has also high efficiency in breeding with regard to cold resistance, drought tolerance, lodging, plant height. This was achieved thanks to the phylogenetic proximity of bread wheat (Triticum aestivum) with wild species as representatives of Aegilops, Haynaldia, Agropyron, Elytrigia, Elymus, Leymus. Wide hybridization is useful in order to obtain haploid plants resulting in valuable homozygous lines. The utilization of crosses as Triticum x Zea, Triticum x Imperata, Triticum x Pennisetum allows rapid elimination of the paternal chromosomes in the meiotic division. The method of wide hybridization was successfully used to combine the genomes of valuable cultivars. Thus amphidiploid cultural species as Triticale (Triticum x Secale) and Tritordeum (Triticum x Hordeum) are successfully obtained. However, wide hybridization is related to the problems of heredity. The low percentage of crossability due to incompatibility of the stigmas of maternal plants and pollen of the paternal plants set the large number of crosses that should be handled. In many crosses there are different types of genomic incompatibility – preembryonic (receiving reduced seedset), embryonic (low percentage of germination of the seeds) postembryonic (high degree of sterility of the obtained hybrids). Low viability and the hybrid necrosis is also an essential disadvantage of wide hybrids. Using techniques such as colchicine treatment, anther culture and embryo culture are means to overcome difficulties in wide hybridization and make it a promising method of breeding in the Poaceae.