**1. Introduction**

Gametophytic selection is the selection of genotypes in the sexual (haploid) generation of a plant's life cycle. Gametophytic selection is based on the different selective value of gametes, due to their genetic diversity. In this case, both micro and macrogametophytes can be subject to selection.

Selection in the haploid phase is widespread in higher plants. However, it was only recently shown that a significant part of the plant genome is expressed in the haploid phase and that a fairly large part of it is common for the sporophyte. The extensive overlap between the gametophytic and sporophytic phases constitutes the biological basis for the sporophyte response to gametophyte selection. Given that selection at

the haploid level and, especially, in the male gametophytic generation, is capable to cause a significant shift in the genetic structure of populations in a short time, it can be actively involved in the breeding practice to search for valuable genotypes.

If each phase of a plant's life cycle had its own set of expressed genes, then selection at the gametophytic level would only lead to changes in the next gametophytic generation and would not affect the sporophyte. However, the results of numerous studies on the influence of gametophytic selection on sporophytic offspring [1–14] indicate that there is a significant degree of overlap between the two phases of the life cycle. It is believed that approximately 60% of the structural genes expressed in pollen are also expressed in the sporophyte [15–16].

Selection can operate in both the male and the female gametophytic generations. However, given the large size of the population of male gametes, the relative independence of pollen grains from the mother plant, the possibility of direct impact on them by environmental factors, the competition of many gametophytes within one style, male gametophytic selection, in comparison with female selection, is considered more effective. It is often compared to selection in microorganisms, given the large population size and the haploid state of the genome [3, 16, 17].

Considering the significant degree of genetic overlap of both phases of the plant life cycle, it is believed that the efficiency of gametophyte selection, especially pollen, may be higher than that of sporophyte [16]. This is explained by the fact that, firstly, the size of the population of male gametophytes is much larger than the size of the population of sporophytes. This makes it possible to apply high selection pressure. Secondly, it is much more difficult to obtain the desired gene combination at the sporophyte stage than at the gametophyte stage as the sporophyte of higher plants contains a double set of genes compared to the gametophyte. Because of this, the probability of selecting a complex combination of alleles is higher in the gametophytic generation. And thirdly, the haploid state of the gametophyte allows direct access to the recessive alleles.
