Effect of manganese- and selenium-containing nanocomposites on soybean resistance to Pectobacterium carotovorum and microbial landscape of soybean seedlings

The main objective of this study was to test how two chemically synthesized selenium (Se) and manganese (Mn) nanocomposites (NCs) based on the water-soluble polysaccharide arabinogalactan (AG) would separately and together affect the phytopathogenic bacterium Pectobacterium carotovorum and microbiome of soybean (Glycine max (L.) Merr.) seedlings, as well as their resistance to the infection caused by P. carotovorum. After nanopriming, seed germination, biometric traits (mass and length of the root and hypocotyl) and biochemical parameters (content of reactive oxygen species, activity of antioxidant enzymes, amount of lipid peroxidation products) of soybean seedlings were analyzed. It was shown that treatment with NCs increased germination rate of seeds infected by P. carotovorum by 50%. In addition, all biometric traits of these seedlings were improved compared to the control. A significant increase in diene conjugates (DC) was also noted in the hypocotyl tissues of their roots. The joint treatment by Mn/AG NC in combination with Se/AG NC (5.92% Se) also stimulated an increase in the length and mass of the roots in both uninfected seeds and infected seedlings, reduced the amount of reactive oxygen species (ROS) and peroxidase (POD) activity in the root tissues and DC in the hypocotyl tissues, and reduced the amount of pathogenic Bacillus spp. bacteria in the endomicrobiome of soybean seedlings. Thus, the Mn/AG and Se/AG NCs, separately or together, can be considered effective agents that have an antibacterial effect against phytopathogens and increase the resistance of soybeans to bacterial diseases caused by P. carotovorum.