The article presents an analysis of the artificial dehydration effect of peach leaf tissues, simulating natural drought, on various physiological, morphological, and anatomical parameters described in the literature, associated with the trait of drought resistance. An investigation aimed to identify the most informative criteria for peach drought resistance which correlate with water loss during dehydration. The results present an assessment of the amount of water loss in 60 peach cultivars selected from different geographical areas and having different genetic origins. Four contrasting genotypes were identified, based on the results of the cluster analysis performed on the cultivar’s water regime. The influence of water regime parameters (leaf water content, water saturation deficit, dynamic of water loss), the morphological and anatomical structure of the leaf, the content of photosynthetic pigments, and the activity of the photosynthetic apparatus on drought resistance were investigated for selected peach cultivars. It was revealed that the most informative criteria for assessing drought resistance were dry and fresh leaf weight, leaf blade length, leaf width, and area (among morphometric parameters); stomatal pore length, stomata density, adaxial and abaxial epidermis thickness, and adaxial cuticle thickness (among anatomical parameters); and Fv/Fm—maximum photochemical quantum yield of PSII, Y(NO)—quantum yield of unregulated non-photochemical light energy dissipation in PS II and Y(NPQ)—controlled quantum losses (among indicators of photosynthetic activity).

The objective of the research was to study the diversity of cultivated species and varieties of Actinidia Lindl., assess the status and analyze the trends pertaining to the cultivation of various Actinidia spp. in order to find out whether it is possible to cultivate them in the Crimea. The fruits of Actinidia chinensis var . deliciosa (A. Chev.) A. Chev. (kiwi) are among the most valuable subtropical fruit plants. The leader among the main kiwifruit-producing regions is Asia (54.5%), and significant amounts are produced in Europe (24.1%) and Oceania (14.4%). The largest producer of kiwi is China; in 2023, this country harvested 54.0% of the global production. Besides, significant harvests are collected in Italy and New Zealand, and somewhat less in Chile, Iran, and Greece. Until 1999, the world production of kiwi was about one million tons. A steady production growth and the expansion of cultivation areas have been observed since 2000. In 2023, the production increased 4.9 times compared to 1994, and the area 4.8 times. FAO reported a significant increase in the production of A. chinensis var . deliciosa fruits, and new trends towards the cultivation of A. kolomikta (Maxim. et Rupr.) Maxim., A. arguta (Siebold е t Zucc.) Planch. ex Miq., and some other Actinidia spp. The breeding work in the Nikita Botanical Gardens has been aimed at the development of cultivars of A. chinensis var. deliciosa that are most adapted to the conditions of the Crimea, and a new cultivar, ‘Nikitskaya Yubileynaya’, has been released. Producing new Actinidia cultivars acclimated to the most favorable areas for their cultivation will expand the range and increase the production of fruits in Russia.

Understanding the transcriptional responses of plants under cold stress conditions is critical for olive cultivation, particularly in regions prone to extreme weather fluctuations and especially with increasing threats from climate change. In controlled experiments, we subjected leaves of three cold-tolerant and three cold-susceptible cultivars to moderate (−7 °C) and severe (−12 °C) freezing stress, followed by recovery at baseline temperatures. The study measured photosynthetic efficiency and enzymatic activity and showed physiological and gene expression changes using different methods. Distinct transcriptomic adaptations were revealed. Cultivars displayed enhanced differential expression associated with photosynthetic recovery and gene regulation in metabolic pathways. Two overlapping DEGs with increased expression were found in all cultivars during initial freezing.

ISHS VIII International Scientific and Practical Conference on Biotechnology as an Instrument for Plant Biodiversity Conservation (Physiological, Biochemical, Embryological, Genetic and Legal Aspects) Drought resistance and photoactivity of leaf apparatus of peach cultivars under conditions of the southern coast of Crimea

Background.Olive (O. europaeaL.) is one of the main fruit crops in the world. It is most widespread in the Mediterranean region. In recent years, due to global warming and aridization of the earth, most olive-producing countries have suffered significant losses and are forced to transfer olive plantings from the traditional southern regions to the more humid northern ones. Insufficient precipitation and lack of irrigation water are currently some limiting factors in this crop's spread. Producers are increasingly focusing on planting drought-resistant cultivars that could produce high and regular yields in conditions of insufficient water supply. In this regard, this study aimedto identify genotypes of O. europaeawith high adaptive ability to the arid conditions of southern Russia and to determine the most informative indicators of drought resistance for collection screening. Materials and methods.Studies of water regime indicators (water-holding capacity, water deficiency, water content) and relative electrolyte yield, when the cell membrane is damaged under conditions of dehydration of leaf tissues, were carried out on 60 intraspecific hybrids of European olive. Corregiolo and Ascolano cultivars served as the control. The experiments were performed in laboratory conditions under controlled temperature of 30°C and relative air humidity of 30%. After leaf tissues' saturation with water (control), as well as after they were dehydrated for 24, 48 and 72 hours, drought resistance indicators were assessed. Results.Based on a cluster analysis, the main indicators of drought resistance, four groups of olive genotypes with different resistance to drought were identified. The greatest interest is for hybrids in the group with very high drought resistance. This cluster consists of 14 of the most promising hybrids that are superior in drought resistance to the control olive variety Ascolano. Water loss for these accession varied from 20.81 to 33.63%, and the relative yield of electrolyte varied from 0.27 to 0.36 RU, which allows us to conclude that their drought resistance is very high. Based on the analysis of principal components between various criteria of the water regime of olive plants, the relationship and influence on the integral assessment of drought resistance was shown. It is noted that the most informative indicator, which has a negative correlation with water loss and the relative yield of electrolytes when the cell membrane is damaged, is water-holding capacity. Indicators of drought resistance such as water content in leaves, water deficit, and relative water content in leaves are not sufficiently informative for the selection breeding of drought-resistant cultivars and forms of olive.

Background. Olive (O. europaea) is a popular fruit crop, and is the second in the world by area after coffee. The main limiting factor for olive cultivation in regions located on the northern border of the subtropical zone, as well as in temperate climates, is their low frost resistance. So, the aim of the present study was to evaluate the degree of influence of low negative temperatures on the functional state of leaves of different O. europaea genotypes. Materials and methods. The functioning of pigment apparatus, stability of chlorophyll-protein complex and membrane damage under freezing temperatures were evaluated on leaves of the following cultivars of olive: ‘Aglandau’, ‘Coreggiolo’, ‘Obilnaya’, ‘Tiflis’, ‘Dalmatica’, ‘Nikitskaya 2’, ‘Ascolano’, ‘Tossijskaya’, ‘Leccino’, ‘Razzo’. The studies were carried out under native conditions (control) and after exposure to low temperatures (immediately and after 24 hours of the stress factor influence). Four temperature effects were analyzed: -7°C, -10°C, -12°C and -14°C. Results and conclusion. Exposure to sub-zero temperatures induced a different response both in the manifestation of visual lesions on leaves and in changes in their physiological parameters. At a low gradient of temperature exposure (-7... - 10°C), leaf tissues of the European selection varieties ‘Coreggiolo’, ‘Ascolano’, ‘Leccino’ and ‘Razzo’ were damaged: electrical conductivity reached 15%, chlorophyll stability index decreased, variable fluorescence and photosynthetic activity coefficients decreased, uncontrolled photon quenching was significantly higher than the effective photochemical quantum yield and non-photochemical quenching. Cultivars of crimean and caucasian breeding are characterised by increased frost resistance. Cultivars ‘Nikitskaya 2’, ‘Tossijskaya’ and ‘Tiflis’ demonstrate integrity of leaf cell membranes, preservation of stability of photosynthetic pigments content and work of photosystems at different levels of their organization at –14°C. EDN: WTGVZM