Relevance. Plant growth biostimulants based on natural raw materials are ecologically safe and harmless to humans. Stevia (Stevia rebaudiana Bertoni) contains in its leaves sweet diterpene steviol glycosides, which are similar in structure and properties to gibberellins, as well as a number of other valuable biologically active compounds. Water extracts from stevia leaves are capable to accelerate growth, to increase the yield and quality of plants. However, further study and development of application technologies of the extracts for specific crops and different growing conditions are required. The purpouse of this work is to investigate the effect of an aqueous extract from stevia leaves on the yield and quality of lettuce and small radish under photoculture conditions. Materials and methods. The objects of the study were lettuce var. Typhoon and small radish var. Riesenbutter. The plants were grown in photoculture at the biopolygon of the FSBSI Agrophysical Research Institute (St. Petersburg) at an illumination of 10–20 klx, a temperature of 22–26°С (day) and 18–20°С (night). Watering was carried out with water, top-dressing was carried out with Knop's nutrient solution three times a week. Peat with mineral additives was used as a substrate. The original extract was prepared by extraction from stevia dry leaves powder with hot water (80°С) in a ratio of 1 g of leaves: 100 ml of water. Foliar treatment of plants was carried out twice at dilution of the original extract from stevia leaves 1:10, 1:50, and 1:100 (extract : water) at the rate of 0.20-0.25 ml / lettuce plant and 0.09-0.1 ml / radish plant; control plants were treated with water. The data were processed according to standard procedures using the Excel 2016 software. Results. Foliar treatment with an extract from stevia leaves did not significantly affect the size and weight of radish root crops, but increased the yield due to a decrease in the number of bolting plants. A significant decrease of bolting was observed in all treatment options (by 34-51%). When using a dilution of 1: 100, the yield of marketable root crops increased by 20% and the yield per sq. m. – by 25%. Foliar treatment with stevia extracts increased the mass of lettuce plants, as well as their biological value. The content of photosynthetic pigments, sugars, and vitamin C significantly increased, and a tendency towards a decrease in the content of nitrates was observed. According to data, we recommend for foliar treatment are dilutions of the original extract 1:50 and 1: 100. The effect of using of an extract from stevia leaves is similar in action to some biostimulants from plants with hormone-like properties, which determines the possibility of using it as a safe plant growth stimulant.

During the last decades increasing the harmfulness of virus pathogens on crops, in particular Bean yellow mosaic (BYMV) was observed grown in intensity. The causative agent as most members of the Рotyvirus genus, has a wide range of host plants belonging to various families including Fabaceae. The distribution area of BYMV considerably expanded after advancement of heat-loving leguminous crops towards the north. During the last years epiphytotics were reported in the planted crops of kidney bean (Phaseolus vulgaris L.), and Russian bean (Faba bona Medik. var. major Harz.) under conditions of temperate continental climate of the nonchernozem belt in Russia. Searching BYMV resistance sources and creating a starting breeding material are priorities in the phytopathological research. The tasks of this stage included: identification and study of the properties of BYMV Moscow isolates; integral assessment of resistance and other economically valuable characteristics of collection material and breeding stock material of kidney bean (810 specimens) and Russian bean (40 specimens) generated in the Federal Scientific Vegetable Center. To achieve the goal visual, serological diagnostic methods were used together with biotesting and electron microscopy. The research revealed special physical-chemical characteristics of BYMV Moscow isolates characterized by 100% harmfulness when occurred as co-infection with the other viruses. The main symptoms caused by the above isolates in indicator plants and host plants under conditions of the Moscow Region have been described. Evaluation of collection and selection materials of kidney bean and Russian bean formed the basis for identification of the sources of resistance to BYMV exhibiting integrated economically valuable properties (early ripeness, bean shape and color, productivity, etc.). These specimens have been included into selection program for creating high productive green bean varieties meeting the requirements of the modern market. | В последние десятилетия отмечено нарастание вредоносности вирусопатогенов на посевах с.-х культур, в частности вируса желтой мозаики фасоли – ВЖМФ (Bean yellow mosaic – BYMV). Возбудитель, как и большинство представителей рода Рotyvirus, имеет широкий круг растений-хозяев из различных семейств, в том числе и из Fabaceae. В последние годы эпифитотии регистрированы на посевах фасоли обыкновенной (Phaseolus vulgaris L.) и бобов овощных (Faba bona Medik. var. major Harz.) в условиях умеренно-континентального климата Нечерноземной зоны РФ. Поиск источников устойчивости к ВЖМФ и создание исходного материала для селекции является в настоящее время приоритетным направлением наших фитопатологических исследований. В задачи данного этапа входили идентификация и изучение свойств московских изолятов ВЖМФ; комплексная оценка устойчивости и других хозяйственно ценных признаков коллекционного и селекционного материала фасоли овощной (810 образцов) и бобов овощных (40 образцов) лаборатории селекции и семеноводства бобовых культур Федерального научного центра овощеводства. В работе использовали методы визуальной диагностики, серологической диагностики, биотестирования и электронной микроскопии. На основании проведенных исследований выявлены особенности физико-химических характеристик московских изолятов ВЖМФ, вредоносность которых в смешанной инфекции с другими вирусами доходила до 100%. Описаны основные симптомы, вызываемые данными изолятами на растениях-индикаторах и на растениях-хозяевах в условиях Московской области. На основе оценки коллекционного и селекционного материала фасоли овощной и бобов овощных выделены источники резистентности к ВЖМФ с комплексом хозяйственно ценных признаков (скороспелость, форма и цвет боба, продуктивность и др.). Данные образцы включены в селекционную программу по созданию высокопродуктивных сортов фасоли овощной, отвечающих требованиям современного рынка.