*2.5.2 Effect of selection of pollen resistant to high temperature in F1 on drought tolerance of F2 sporophytes in maize*

The effectiveness of gametophytic selection for drought resistance in maize can be demonstrated using the example of the VIR27 × MK01 hybrid. Its parental components were contrasting in resistance to high temperatures at the haploid and diploid stages of development.

To carry out the selection, the pollen of the hybrid was heated at the temperature of 35°C for 5–20 min. After heating, that pollen was used for self-pollination of the

hybrid, having previously determined its viability on an artificial nutrient medium. For pollination, the pollen was used, which reduced its viability after heating by at least 80%. Pollination of each ear was carried out with a limited amount of pollen in order to exclude competition between haploid genotypes during pollen germination and pollen tube growth. Seeds (*F*2 sporophytes) obtained after pollination of *F*1 plant with fresh (control) and heated (treatment) pollen were sprouted in a solution with an osmotic (18 atm) and after a certain time, the percentage of germinated kernels was calculated.

As a result of heating the heterogeneous pollen population of this hybrid, the number of germinated seeds after 8 and 12 days under conditions of osmotic stress was 1.5 and 7.0 times higher than in the control. The data obtained allow to conclude about high efficiency of selection for drought resistance at the stage of mature pollen in maize.

High-temperature conditions when exposed to pollen are inevitably accompanied by low air humidity. Obviously, different reactions of haploid genotypes to high temperatures are due to different states of the membrane of pollen grains in genetically different haploid genotypes. Pollen grains resistant to these thermal treatments are characterized by such a membrane complex, which allows better water retention. As a result, such pollen retains its viability longer.
