Background. Studying the effect of phytohormones and light on the germination of apple pollen with reduced viability on an artificial nutrient medium is of importance, because it may facilitate an increase in the germination percentage among plant samples promising for breeding after their long-term preservation under low temperatures.Materials and methods. Pollen viability of the apple-tree cultivar ‘Krasnolistnaya’ was measured by germinating it on an artificial nutrient medium containing 10% sucrose solution and 0.8% agar. Drops of a distilled water suspension of pollen with added phytohormones were applied to the surface of the nutrient medium. Pollen was germinated in the dark (24 hours in a thermostat at 21°C) and under light (in an artificial light chamber at 21°C with a photoperiod of 16 hours of light / 8 hours of darkness). Results. Pollen of cv. ‘Krasnolistnaya’ with reduced viability most effectively germinated with the use of gibberellin at a concentration of 1 mg/l and 10 mg/l: the germination percentage was 22.3±0.8% and 21.8±1.3% respectively (сf. 10.9±1.5% in the reference). The most effective combination of phytohormones was gibberellin 10 mg/l + kinetin 10 mg/l – the percentage of germination was 22.8±6.3%; kinetin 1 mg/l + indolylbutyric acid 1 mg/l – the percentage of germination was 17.5±5.9% vs. 10.9±1.5% in the reference.Conclusion. Phytohormones were observed to have a significant effect on the germination of apple pollen with reduced viability. Effective concentrations and combinations of phytohormones that promote the germination of pollen with reduced viability have been identified. Light does not affect the germination of pollen with reduced viability.

This work is devoted to the possibilities of using a specific intron-containing block of the Nxf1 gene in phylogenetic studies. Our attention was drawn to the conservative intron of the Nxf1 (nuclear export factor) gene. This intron is a part of an evolutionarily conserved block formed with flanking 110 bp and 37 bp exons, similar in representatives of various taxonomic groups. This evolutionary conservative block in our previous works was designated cassette intron. The Nxf1 genes are found in all representatives of Opisthokonta, and may be a convenient object for phylogenetic studies. The Nxf1 gene sequences of seventeen representatives of the order Chiroptera obtained from publicly available databases (ensembl, ncbi). Alignment algorithm: MUSCLE. Programs: MEGA-X version 10.1.7, IQTree, Mesquite, MrBayes, and FigTree.v1.4.4. Estimation methods: Maximum Likelihood and Bayes Inference. The use of Nxf1 gene sequences that include only exons or only introns leads to unequal loss of accuracy in establishing evolutionary relationships in comparison with the model based on the complete gene sequence. Sequences involving all exons plus a cassette intron give the same result as the complete Nxf1 gene sequence. The obtained results indicate the importance of the cassette intron in the evolution of the Nxf1 gene of Chiroptera.

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