Objective: Evaluate the antifungal effect of chitosan against Rhizoctonia solani in vitro and the possible mechanisms of its induced activity in potato tubers to control black scurf disease. Methods: The in vitro influence of chitosan at different concentrations on mycelial growth of R. solani was tested by using the poisoned food technique in PDA medium. The effect of these concentrations on the development of lesion diameters in tubers inoculated with R. solani mycelium was assayed for 30 days. The concentration that showed the greatest inhibitory effect on lesion diameters was tested to assess the induced activity of defense-related enzymes in the infected tubers. Results: In the poisoned food technique, chitosan at 1% completely inhibited the growth of R. solani mycelium. In vivo tests showed that chitosan treatment at 0.5% effectively controlled the black scurf in tubers inoculated with R. solani mycelium. Chitosan increased the activities of defense-related enzymes such as Peroxidase (POD), Polyphenol Oxidase (PPO) and Phenylalanine Ammonia-lyase (PAL) in treated tubers of tested cultivars. Conclusion: This work demonstrated that chitosan directly inhibited the growth of R. solani, and potentially elicited defense reaction in potato tubers.

In the article the results of studying the peculiarities of mildew development by the macroscopic diagnostics method on the examples of 33 varieties and hybrid grapes forms in the conditions of the steppe zone of the Lower Volga Area have been reported. Indicators of the maximum infection of leaves, inflorescences and medium infection of vegetative and reproductive organs were characterized by the greatest degree of susceptibility to mildew. The degree of mildew’s distribution and development changed from year to year depending on the current year weather conditions and the features of its development in the previous year. During the seven-year period of observations three years were characterized by epiphytoties mildew. As a result of studying of grapes resistance to mildew, groups of irresistant, tolerant and resistant varieties have been distinguished.

The data of long-term research aimed at improving the forage reserve in order to provide livestock with high-grade concentrated green fodder and silage are presented. The necessity of selection and comparative assessment of maize hybrids of different early maturity and improvement of the basic methods of cultivation technology has been substantiated. The seeding rates slightly changed the field germination rate. On average for 2017–2019 at a seeding rate of 50 thousand seeds per 1 hectare by the panicle-sweeping phase, the leaf surface of the mid-early hybrid Rainbow was 31.2 thousand m2/ha, which is 9.5% higher compared to the early-ripening hybrid Mashuk 185 MV ( 28.5 thousand m2/ha) and 14.3% higher compared to the ultra-early hybrid RNIISK-1 (27.3 thousand m2/ha). With an increase in the seeding rate over 50 thousand seeds per hectare, the leaf surface of all hybrids increased and was maximum at 70 thousand seeds per hectare. The minimum leaf area was at a seeding rate of 40 thousand seeds per hectare. Similarly to the formation of the leaf surface, the accumulation of green and dry biomass took place depending on the seeding rate in the ultra-early maize hybrid RNIISK-1. In the early-maturing hybrid Mashuk 185 MV and the mid-early hybrid Raduga, the accumulation of green and dry biomass did not depend on the seeding rate. Such features of the growth and development of maize hybrids, depending on the seeding rate, influenced the structure and size of the grain yield.

Potato gangrene is a very dangerous disease developing during storage and can lead to serious crop losses. The main control of this pathogen is reported by the post-harvest use of fungicides. However, the pathogen resistance to fungicides and public concerns about food safety require the search for new alternatives to fungicides, potentially less harmful to human health and the environment. The antifungal influence of chitosan against Phoma exigua var foveata and analyzing its inhibitory effect on the gangrene of potato tubers were investigated. The results showed that the growth of the mycelium and the germination of Phoma spores were suppressed by chitosan treatment, and the inhibitory effect was strongly correlated with the chitosan concentration. The effectiveness of post-harvest chitosan treatment has been studied for induced resistance to Phoma rot in tubers of two potato varieties (Kolobok and Santa). In vivo studies have shown that chitosan treatment at a concentration of 0.5 or 1% effectively combated gangrene potato tubers inoculated with a suspension of Phoma spores. However, treatment with chitosan at a concentration of 1% caused phytotoxicity of potato tubers. Chitosan increased the activity of peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase in tubers. This study suggests that the influence of chitosan may be related to the induced resistance of potato Phoma rot, and the use of chitosan may be a promising agent as a natural fungicide for partial replacement of synthetic fungicides to protect potato tubers during storage.

The data of studies on the selection and comparative assessment of the productivity of different early maturity groups of maize hybrids: ultra-early maturing - Ross 140 SV, RNIISK-1, NUR, Baikal; early maturing - Mashuk 175 MV, Mashuk 185 MV, Rodnik 180 SV, Darina MV; mid-early - Dokuchaevsky 190 SV, Krasnodar 194, Raduga, Mashuk 250 SV. All studied hybrids were distinguished by high laboratory germination capacity. Their field germination rate varied from genetic characteristics by no more than 2.1–2.8%, mainly depending on weather conditions. The features of the formation of the leaf surface, green and dry biomass, depending on the group of ripeness of the hybrids, were revealed. The maximum indicators of leaf surface formation (42.01 thousand m2), photosynthetic potential (2917 thousand m2 / ha · day) and dry biomass (9.28 t / ha) in the panicle-sweeping phase were in the mid-early hybrid Rainbow. The maximum grain yield (5.84 t / ha) was in the mid-early hybrid Raduga, which is 0.9 t / ha higher compared to the early-maturing hybrid Mashuk 185 MV and 1.16 t / ha higher than the ultra-early hybrid RNIISK- 1.