Background. One of the ways to use the genetic potential of bulbous barley, which is characterized by a number of valuable traits, is interspecific hybridization. In crosses of H. vulgare (2x) × H. bulbosum (2x) and H. vulgare (4x) × H. bulbosum (4x) with a genome ratio of 1Hv: 1Hb in a hybrid embryo, elimination of bulbous barley chromosomes is observed in many cases, and the intensity of the process and the result of the crossing depend on the genotypes of the parental forms. This limits the possibility of including a significant variety of parental forms in crosses. Сrossing of diploid forms of H. vulgare with tetraploid accessions of H. bulbosum (4x) results in the formation of triploid hybrids (HvHbHb) with stable chromosomal composition in pollen mother cells (PMCs) at metaphase I (MI) of meiosis. These triploid hybrids can serve as a basis for obtaining series of introgressive lines of cultivated barley. One of the tasks of this type of work is to estimate the involvement of various chromosomes and their arms in homoeologous associations. The aim of this work was to study the possibility of homoeologous pairing of chromosomes of parental species at MI of meiosis in triploid hybrids using GISH and FISH with chromosome-specific markers, as well as to register the participation of individual arms of the cultivated barley chromosomes in homoeologous associations with the chromosomes of bulbous barley in triploid hybrids (HvHbHb).

Materials and methods. Seven triploid hybrids of H. vulgare × H.bulbosum (HvHbHb) obtained in four combinations of crosses with the participation of three diploid cultivars of cultivated barley and two tetraploid accession of bulbous barley were used in this study. The features of homoeologous pairing of chromosomes at MI were studied using the method of fluorescent in situ hybridization (GISH and FISH) with chromosome-specific markers.

Results All the studied hybrid plants are characterized by a stable chromosomal composition in PMCs at the MI stage of meiosis. Meiotic configurations formed by homoeologous chromosomes of the parental species, ranging from 0.87 to 1.40 on average per cell, were identified in all the studied plants. Among them, vbb trivalents prevailed. Analysis of chromosome pairing at MI in triploid hybrids revealed the participation of all chromosome arms of H. vulgare in homoeologous Hv-Hb associations, except for the short arm of chromosome 1H. In all the studied triploid hybrids, there is a tendency for a higher frequency of involvement of the long arms of chromosomes in the formation of homoeologous associations; this feature is most clearly manifested in case of chromosome 5H.

Conclusions Intergenomic associations with the participation of all arms of H. vulgare chromosomes, except for the short arm of chromosome 1H, were revealed at MI in H. vulgare × H. bulbosum triploid hybrids (HvHbHb). Chromosome 5H, as well as any other cultivated barley chromosome, is characterized by a higher involvement of its long arm in homoeologous associations Hv-Hb, as compared to the short arm.

The discovery of spontaneous haploid plants and the development of ways to produce them in in vitro culture have set a new direction important for breeding and for theoretical research in reproductive biology. The frequency of spontaneous haploidy in cultivated plants is extremely low and does not exceed 0.01-0.1%, therefore, the search for sources and donors capable of stimulating haploidy in hybrid combinations is of current interest. Expansion of the search for new sources and donors of the haploinduction trait, the creation of new, more effective haploinducers contribute to the accumulation of scientific information and genetic sources, characterized by a high resource potential for selection and genetic research. The causеs of haploidy are not well understood yet. According to the available information, the genes localized in the qhir1, qhir11, qhir12 regions of chromosome 1 in maize are responsible for this process. The use of genes that stimulate haploinduction in maize in combination with the marker gene R1-nj responsible for anthocyanin coloration of the caryopsis and embryo, as well as genes A1 and B1, which are in control of the entire plant coloration, allowed the creation of haploinducer lines with a frequency of haploid stimulation up to 15%. Phenotypic expression of dominant alleles of the marker anthocyanin coloration genes in different parts of a hybrid plant, as well as in the caryopsis and embryo, contributes to the high-quality selection of haploid kernels in the cob due to the manifestation of recessive alleles of these genes at the haploid level. The presence of anthocyanin synthesis suppressor genes in siliceous maize (C1-I, C2-Idf, In1-D) restricts the use of the R1-nj gene in other representatives of siliceous maize. In order to overcome this problem, studies are underway to create other genotypes of haploinducers, which are not associated with the anthocyanin coloration of the caryopsis, but instead have other marker traits, such as the oil content in the kernel, the absence of ligules in the leaves, and root coloration in seedlings. The use of matroclinous and androclinous types of haploinduction allows breeders to obtain highly homozygous dihaploid maize lines, with both the maternal and paternal genomes. These achievements made it possible to cut five or more times the material and time inputs into the creation of inbred lines and their sterile analogs, accelerate the breeding of new maize hybrids, and signifi cantly improve the quality of seed production in terms of typicality and uniformity. The materials presented in the article should help breeders and geneticists to learn more about the innovative directions and problems of hybrid maize breeding.

This paper reviews the results of studies of interspecies hybridization, polyploidization, as well as phylogenetic relationships of Solanum species and members of closely related taxa by such molecular cytogenetic techniques as genomic (GISH) and fluorescent (FISH) DNA-DNA in situ hybridization. The latter was used to determine the genomic composition and origin of wild species of the Petota section, while the FISH technique was used for detecting intergenomic collinearity. The combination of these two types of research made possible a comparative analysis of karyotypes and genomes, thus allowing a better understanding of the meiotic interchromosomal interactions in hybrids. This review primarily focuses on the studies of wild allopolyploid potato species and artificially created intergeneric and interspecific hybrids of the genus Solanum and their offspring.