Prospects for the use of various species and strains of symbiotic bacteria (<i>Xenorhabdus sp.</i>) in the biological protection of potatoes from diseases in the European North of Russia

Abstract

Research on the development of environmentally friendly plant protection systems against fungal pathogens using symbiotic bacteria Xenorhabdus sp. – symbionts of entomopathogenic nematodes (EPN) has been a new direction in agricultural practice in recent years and undoubtedly represent relevance and scientific significance. The studies used suspensions of live and autoclaved cultures of symbiotic bacteria of symbionts of various types of EPN (Steinernema carpocapsae, S. feltiae and S. feltiae protense) with a bacterial cell titer of 107 CFU/ml in comparison with the biological preparation Phytosporin-M (dough) and water as a control. In laboratory conditions at a temperature of 25 oC, there were established differences in the antibiotic activity of the primary forms of producers of Xenorhabdus sp., isolated from different types of EPN. The greatest inhibition of the fungal growth zone on the 4th day was observed for metabolites of the S. carpocapsae strain against Alternaria solani. Biological effectiveness in suppressing this pathogen was 51 %. Field research conducted in 2022-2023 in the conditions of the Republic of Karelia on the mid-early potato variety ʻRed Scarlettʼ, showed that under epiphytotic conditions (low air temperatures and excessive waterlogging) double spraying of vegetative plants with a suspension of live and autoclaved cultures of symbiotic bacteria (EPN-1-1, EPN-2 and EPN-2 -1) reduced the development of rhizoctoniosis compared to the control variant by 50, 64 and 60 %, respectively. It was found that double treatment with a live and autoclaved aqueous suspension of bacteria, symbionts of the subspecies S. feltiae was more effective and ensured a reduction in the degree of development of scab symptoms by 1.3–2.8 times and the spread of rhizoctonia by 1.5–2.0 times. It has been also established that 2-fold spraying of plants with a live and autoclaved suspension of symbiotic bacteria S. feltiae during the growing season significantly increases the yield of tubers by 35–22 %, respectively. Thus, the use of biologically active secondary metabolites of Xenorhabdus sp. has significant potential as biological plant protection agents against potato pathogens.