The Concept of Allelic and Nonallelic Mechanism of Heterosis

Heterosis is widely used in crop production to increase crop yields and is applied to more crops. Until the middle of the twentieth century, the mechanism of heterosis was due mainly to the hypotheses of domination and overdominization. From the middle of the 50s of the XX century to the beginning of the 21st century, a number of hypotheses emerged in explaining the mechanism of heterosis, among which are: genetic, metabolic and bioenergetic balances. On the problem of the mechanism of heterosis, one must return to a detailed analysis of the genetics of traits. The emergence of heterosis in the hybrids of the first generation can be explained on the basis of allelic and non-allelic gene interaction, which creates a favorable combination of genes during hybridization, which causes a better manifestation of an economically valuable trait. Allelic interaction of genes is mainly manifested in the complete or incomplete dominance of the dominant gene over the recessive gene of one allelic pair, as well as in codomination, when the external manifestation of the trait is a mixture of the action of both alleles of one allelic pair. Intergenic interaction of genes, as a rule, is expressed in four basic forms: complementarity, epistasis, polymorphism and modifying action. In connection with the fact that practically all forms of intergenic nonallelic and allelic interaction of genes are observed in the mechanism of manifestation of heterosis, this phenomenon is still difficult to explain to nature. In the work, somatic heterosis in arabidopsis was studied on the basis of the "diameter of the rosette of leaves". It was established that when the plants of different races Col-0 and La-0 cross in the generation of F2, polymeric interaction of the genes takes place. In this case, the splitting in F2 goes in a ratio of 15:1. In this case, hybrids of the first generation have somatic heterosis, which manifests itself in a more powerful development of the rosette of leaves compared with the original forms. In F1, the Col-0 and La-0 genes in each pair of alleles suppress the dominant gene, which is responsible for the better expression of the "leaflet diameter" attribute, the recessive gene (Col-0 wt, La-0 wt). Hybrid plants of the first generation also have an additive polymer effect of non-allelic dominant COL-0wt and LA-0wt genes to increase the size of the leaf rosette. In the second generation there is a process of splitting hybrids, and their superiority in the diameter of the rosette of leaves over the parental forms is reduced. This is due to a decrease in the