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Bacterial viruses (bacteriophages) have been considered as potential agents for the biological control of bacterial phytopathogens due to their safety and host specificity. Pseudomonas savastanoi pv. glycinea (Psg) is a causative agent of the bacterial spotting of soybean (Glycine max Willd). The harm caused by this bacterium to crop production and the development of antibiotic resistance in Psg and other pathogenic microorganisms has led to the pursuit of alternative management strategies. In this study, three Psg-specific lytic bacteriophages were isolated from soybean field soil in geographically distant regions of Russia, and their potential for protective action on plants was assessed. Sequencing of phage genomes has revealed their close relatedness and attribution to the genus Ghunavirus, subfamily Studiervirinae, family Autographiviridae. Extensive testing of the biological properties of P421, the representative of the isolated phage group, has demonstrated a relatively broad host range covering closely related Pseudomonas species and stability over wide temperature (4–40 °C) and pH (pH 4–7) ranges, as well as stability under ultraviolet irradiation for 30 min. Application of the phages to prevent, and treat, Psg infection of soybean plants confirms that they are promising as biocontrol agents.

Diseases caused by the Gram-positive bacterium Curtobacterium flaccumfaciens pv. flaccumfaciens (Сff) inflict substantial economic losses in soybean cultivation. Use of specific bacterial viruses (bacteriophages) for treatment of seeds and plants to prevent the development of bacterial infections is a promising approach for bioprotection in agriculture. Phage control has been successfully tested for a number of staple crops. However, this approach has never been applied to treat bacterial diseases of legumes caused by Cff, and no specific bacteriophages have been known to date. This paper presents detailed characteristics of the first lytic bacteriophage infecting this pathogen. Phage Ayka, related to φ29-like (Salasmaviridae) viruses, but representing a new subfamily, was shown to control the development of bacterial wilt and tan spot in vitro and in greenhouse plants.

Изложены факторы, способствующие развитию биологического метода защиты растений от болезней: неэффективность химических средств против ряда вредоносных заболеваний, опасность химических препаратов для здоровья человека и окружающей природной среды, удобство и экономическая выгода использования ряда биопрепаратов, соответствие современным требованиям для технологий защищенного грунта, которые предусматривают использование биологических объектов (например, насекомых-опылителей). Представлены теоретические основы биологической защиты растений от болезней – типы экологических отношений между организмами: сосуществование (отсутствие отрицательной зависимости между численностью взаимодействующих популяций), антагонизм (конкуренция за источники питания, антибиоз, паразитизм, гиперпаразитизм). Дана характеристика основным группам микроорганизмов, на основе которых созданы биопрепараты: грибы Trichoderma viride, T. harzianum, T. koningii; Gliocladium virens), бактериии (виды родов Pseudomonas и Bacillus), вирусам и механизмам их защитного действия (для Trichoderma – направленный рост гиф антагониста в направлении к метаболитам гриба-хозяина, оплетение гифов гриба-хозяина и перфорация клеточной стенки хозяина, последующая полная колонизация хозяина, проникновение в мицелий хозяина, активный рост внутри клеток, гибель мицелия гриба-хозяина; для Pseudomonas – образование стабильных комплексов с трехвалентным железом, связывание ионов трехвалентного железа в почве, как следствие – лишение многих видов фитопатогенных грибов необходимого элемента питания, что приводит к остановке их развития). Указано на значение контроля показателей качества препаратов для успешной защиты растений от болезней (титр, чистота и биологическая активность).The factors contributing to the development of the biological method of plant protection from diseases are described: the inefficiency of chemicals against a number of harmful diseases, the danger of chemicals for human health and the environment, the convenience and economic benefits of the use of a number of biological products, compliance with modern requirements for protected soil technologies, which provide for the use of biological objects (for example, pollinators). Theoretical bases of biological protection of plants from diseases-types of ecological relations between organisms are presented: coexistence (absence of negative dependence between the number of interacting populations), antagonism (competition for food sources, antibiosis, parasitism, hyperparasitism). The characteristics of the main groups of microorganisms on the basis of which biological products are given: fungi Trichoderma viride, T.harzianum, T. koningii; Gliocladium virens), bacteriae (species of the genera Bacillus and Pseudomonas), viruses and the mechanisms of their protective action (for Trichoderma – directed growth of the hyphae of the antagonist towards the metabolites of the fungus-host entanglement of the hyphae of the fungus-host and perforation of the cell wall of the host, to the complete colonization of the host, penetration into the host mycelium, the active growth inside the cells, the death of the mycelium of the fungus-host; for Pseudomonas – the formation of stable complexes with trivalent iron, binding of ferric ions in the soil, as a consequence – the deprivation of many species of phytopathogenic fungi necessary element of nutrition, which leads to a halt in their development). The importance of monitoring the quality of preparations for the successful protection of plants from diseases are noted: titer, purity and biological activity.