Morphology of generative organs of Morus alba L. cultivars introduced in the conditions of the Forest Steppe of Ukraine

Purpose. The aim was to study the features of flowering and fruiting of the mulberry under conditions of the Right­Bank Forest­Steppe of Ukraine. Methods. The research was conducted in the forest steppe zone at the experimental base of the Institute of Horticulture of the NAAS in 2021–2023. The subject was plant material of different cultivars of mulberry (Morus alba), propagated from seed progeny of the ‘Krupnoplidna’ variety; self­fertile mulberry plants were used as a control. The morphological description of the structural elements of the reproductive organs and the study of pollen via­bility were carried out according to published methods. The fruiting of the breeding forms was evaluated on a five­point scale. Results. All plants tested were found to have the abi­lity to germinate pollen. The most viable pollen (75.1%) was found in male breeding form No. 5 after 12 hours exposure and a sucrose concentration of 50%. Exposure for 24 hours caused a decrease in germination energy of up to 63.1%. The latter was lowest in the pollen grains of plants of the triploid sample at both sucrose concentrations used. The comparison of morphological characteristics and seed productivity (per fruit) of the breeding forms of M. alba showed the genetic diversity of plants of cultivars of the species, which is manifested in the difference of phenotypic characteristics due to the variability of the range of their expression. Conclusions. The highest rates of white mulberry pollen germination were obtained for breeding form No. 5 – 79.1 ± 0.36% (male specimen) with 25% concentration of sucrose in the nutrient medium. The number of fruits formed on two­year­old shoots was 21–91. The evaluation of the fruiting of the cultivars was 4–5 points, and their infructescences were 2.26–3.97 cm long (large). In general, the study of the morphology of the reproductive organs of the breeding forms of M. alba, each of which forms filled seeds with high germination energy (91–98%), showed the intactness of the reproductive functions of mulberry, which indicates the successful passage of the plants through all stages of organogenesis.