Background.Learning about morphological and biological features of pollen is very important to make correct estimations of plant productivity and breeding efficiency.Materials and methods. The viability of black currant pollen was analyzed in 2019 at the Laboratory for Long-Term Storage of Plant Genetic Resources, N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR). Eleven black currant cultivars of various ecogeographic and genetic origin maintained at Pushkin and Pavlovsk Laboratories of VIR served as the material for the research. Pollen viability was tested on an artificial medium with 10% sucrose and 0.8% agar. Morphological studies were carried out using light and confocal laser scanning microscopy at the Palynology Laboratory and the Core Centrum of Cell and Molecular Technologies in Plant Science housed by the Komarov Botanical Institute (BIN).Results and conclusion. The prevailing adverse weather conditions in 2019 produced a negative impact on the process of male generative structure formation. The level of pollen viability, depending on the cultivar, ranged from 17.98 to 58.60%. After exposure to liquid nitrogen (–196°C) for 6 months, the number of germinated pollen grains increased 1.1 to 3.2 times in all the studied cultivars, except one (‘Pozdnyaya poslevoennaya’, k-7652). A palynomorphological study revealed that reduced pollen viability in some cultivars (‘Krasnoyarskaya 1018’, k-7607; ‘Tsema’, k-25900; ‘Pozdnyaya poslevoennaya’, k-7652) was associated with morphological deviations in the sporoderm structure (small pollen grains, exine thickening and formation of verrucate mesoporium surfaces). A low positive correlation was observed between the level of pollen viability and the diameters of the pore (r = 0.43) and pollen grain (r = 0.27). An insignificant negative correlation was apparent between the level of viability and the exine thickness (r = –0.33).

One of the prospective ways to safely preserve the genetic resources of red and black currant for breeding needs is the cryopreservation of cuttings with dormant buds. Vegetative cuttings of 12 varieties of red and 11 varieties of black currant were harvested in various regions of Russia: North, Northwest, and Central. Their viability after cryopreservation in nitrogen vapors (about −184 °C) under field conditions was studied. For red currant samples, it ranged from 61.2 ± 1.2% to 72.3 ± 3.0%, black currant—from 58.9 ± 1.1% to 73.5 ± 1.9%. In the group of red currant varieties, there were no significant differences in viability between varieties after cryopreservation. In the group of black currant varieties, “Chereshneva” and “Georgiy” had lower viability after storage in liquid nitrogen vapors than the others, 61.1% and 58.9%, respectively. On red currant, dry growing conditions of the experiment year significantly decreased the viability after cryopreservation. Neither black nor red currants revealed the influence of the place of harvesting on the survival of cuttings after cryopreservation. These results indicate the possibility of using cryopreservation to preserve cuttings of red and black currant with dormant buds collected in regions with different climatic environments.

Structural and mechanical properties of fruits during storage are studied for a number of fruit plants. The possibility of predicting losses of fruit products during cold storage is established on the basis of determining the elastic modulus of plant mesocarp tissue.

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.

The long-term storage of the genetic resources of fruit crops for breeding needs can be freely developed by cryopreservation cuttings with dormant buds in liquid nitrogen vapor, but so far, this method has not been practically used for peach. Cuttings with dormant buds of five peach varieties growing in the field gene bank at Krymsk Experiment and Breeding Station of VIR were collected for cryopreservation in 2019–2021. The three-factor analysis of variance showed that the viability of peach cuttings was significantly affected by the year (p < 0.001) and variety (p < 0.001). According to the three-year average characteristics of the cultivars, the analysis of variance showed a significant difference in the viability of the cultivars after cryopreservation (p = 0.004). According to the results of the three years of study, cvs. ‘Podarok Kryma’ (43.3%) and ‘Lucky 24 B’ (44.4%) showed the lowest viability after cryopreservation, significantly lower than cvs. ‘Baby Gold’ (54.4%) and ‘Ustojchivy 90′ (55.6%). Cv. ‘Lyubimets Krasnodara’ (48.9%) occupied an intermediate position. These viability values exceeded the minimum requirement for samples subjected to long-term cryogenic storage in a cryobank. Low-temperature storage of peach cuttings at –5 °C can be used for short-term preservation. After low-temperature storage, the viability of peach cutting amounted to an average of 67.1%.

Conservation at cryogenic temperatures, usually in liquid nitrogen (LN) or in its vapor, is the only reliable method for the long-term ex situ conservation of fruit and berry crops with vegetative reproduction. In this study, five bird cherry (Padus Mill.) varieties of different genetic origin from the bird cherry genebank at the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR, Russia) were tested for their response to cryopreservation in LN vapor (−183–−185 °C). The response included viability under laboratory and field conditions, morphological assessment of the developed plants and biochemical analysis of fruits produced during three consecutive years by plants developed from cryopreserved cuttings. All parameters were compared to those recorded after cold storage of cuttings (−5 °C), a routine mid-term conservation method currently used at the VIR genebank. The initial viability of winter cuttings varied from 86.7% to 93.3%. Six-month cold storage and cryopreservation reduced viability to 53.3–86.7% and 43.3–60.0%, respectively, which was above the 40% viability threshold in all varieties tested. Cuttings after cold storage showed better viability when recovered in the laboratory (80% mean viability) than in the field (58% mean viability); viability of cryopreserved cuttings was not affected by recovery conditions. The results of a two-way analysis of covariance suggested that storage and recovery conditions had the most significant effect on viability (p < 0.0001), while the effects of genotype (p = 0.062) and factor interactions (p = 0.921) were minor. Cryopreservation had little or no influence on morphological parameters of the plants recovered in the field, including plant height, number of shoots, internodes and roots, and root length. Similarly, no effect of cryopreservation was recorded on dry matter content, total sugar content and ascorbic acid concentration in fruits produced by plants developed from the cryopreserved cuttings. These results suggest that cryopreservation in LN vapor is a reliable method for conservation of the bird cherry genetic collection and is worth testing with a broader variety of genotypes.