Purpose. Determine the effect of plant densities and the use of Organic-balance biological preparation on growth, development of photosynthetic potential and seed yield of maize lines, parental components of perspective hybrids (‘Arabat’, ‘Skadovskyi’, ‘Kakhovskyi’, ‘Azov’, ‘Chonhar’, ‘Hileia’ etc.) under conditions of drip irrigation. Methods. Field, morphometric, statistical. Results. In the flowering phase, the maximum differences in the area of the assimilation surface were observed between the maize lines and between variants using different plant densities and Organic-balance biological preparation. The largest indicator of the area of the assimilation surface was at the mid-late line DK445 for a standing density of 70 thousand plants/ha and the use of organic preparation Organic balance – 0.489 m2/plant. Organic-balance biological preparation had a positive effect on the dynamics of the area of the assimilation surface of the lines, had provide an increase of 0.04 m2/plant or 9.5% over individual phases of development compared to untreated control. The maximum value of the net productivity of photosynthesis – 6.78 g/m2 per day, was obtained from the FAO 420 line at a density of 70 thousand plant/ha, in the FAO 350 line was less by 4.3% with a maximum at a density of 80 thousand. plants/ha. For the FAO 290 line, the optimal plant density was 90,000 plants/ha. It was found that the genotype of the line with a share of influence of 81.2 and 85.2%, respectively, is predominantly influenced by the plant leaf area and the net productivity of photosynthesis. The influence of the organic preparation Organic-balance on these indicators was less and amounted to 13.3 and 12.3% respectively. The least influence on photosynthetic parameters was carried out by the density of phytocoenoses (the proportion of influence of 5.5 and 2.5%). Genotype with 82.2% share had the greatest influence on the seed yield of the lineage-parental components of maize hybrids. Part of the impact of the organic preparation Organic balance was 4.0%, plant density – 5.3%. The maximum seed yield of the FAO 290 line was obtained at a density of 90 thousand. growth./ha and organic drug treatment Organic-balance and amounted to 5.15 t/ha. The FAO 350 line showed the highest yield at a stand density of 80,000. growth/ha and treatment with organic drug Organic-balance – 5.46 t/ha. FAO 420, the highest seed yield, formed at a stand density of 80,000 plants/ha – 6.58 t/ha and treatment with organic drug Organic balance – 7.08 t/ha. Organic Balance treatment increased the seed yield by an average of 8.1%. Conclusions. Photosynthetic indicators of maize lines mainly depend on the genotype. Phytocenosis density and treatment with biopreparation have a much smaller effect. Under irrigation, the maximum seed yield was formed by the FAO 420 parent line of 7.08 t/ha. The results obtained indicate that in order to plan the production of seed material of maize lines, which are the parent components of hybrids, their genotypic features, the response to the density of phytocenoses and biological preparation with growth-stimulating action must be taken into account.

Purpose. Developing technology for clonal micropropagation of peppermint (Mentha piperita L.) plants of Ukrainian breeding based on the complex of methods of isolated tissue and organ culture in vitro. Methods. During the experiment, such methods as isolated tissue and organ culture in vitro, clonal micropropagation, detached scion grafting, chemotherapy with adding of virucide Ribavirin to the nutrient medium, biometric and statistical ones were used. Results. The stepped procedure of sterilization that we have developed allows to receive 88–100% of sterile explants. For M. piperita L. introduction into culture and clonal micropropagation, Murashige and Skoog (MS) nut­rient medium appeared to be optimal supplemented with 6-benzylaminopurine (0.75 mg/l), adenine (0.05 mg/l), indole-3-acetic acid (IAA) (0.05 mg/l) and gibberellic acid (0.5 mg/l) on which the reproduction ratio on the 28th day ranged between 1:7 and 1:15. For recovery of plants from viral infection, virucide Ribavirin at concentration of 10 mg/l was added to the nutrient medium. The proposed nutrient medium for rhizogenesis, that contained IAA (0.5 mg/l) and indole butyric acid (IBA) (0.5 mg/l), allows to obtain the frequency of rhizogenesis up to 84–100%. Regenerated plants were adapted to the conditions in vivo on substrate peat : universal soil : perlite : sand in the ratio 2:1:1:1. The survival rate for peppermint varieties amounted to 96–100%. Conclusions. Biotechnological scheme was developed that permits to get healthy, purebred planting material and intensively propagate plants for supplying breeding programs of the Experimental Station for Medicinal Plants of the Institute of Agroecology and Environmental Management of the National Academy of Agrarian Sciences of Ukraine, among which such varieties as ‘Lebedyna pisnia’ and ‘Ukrainska pertseva’ were selected as the most promising for clonal micropropagation.