Biostimulatory activity of root-associated bacillus isolates from nettle (Urtica dioica L.)

Abstract

The objective of this research was to isolate bacteria belonging to the genus Bacillus from the nettle rhizosphere, conduct biochemical and plant-growth-promoting (PGP) characterization of isolates, and examine their biostimulatory effects on the seeds of medicinal plants. Microorganisms were isolated using the agar plate method for bacterial isolation. Biochemical characterization involved evaluating the isolates? ability to produce enzymes such as lipase, amylase, pectinase, protease, cellulose, urease and gelatinase. Plant-growth-promoting (PGP) characterization included evaluation of indole-3-acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production, as well as the ability to mineralize organic phosphorus compounds and solubilize phosphate. The impact of isolates on seed germination and plant growth was studied using summer savory (Satureja hortensis L.) and parsley (Petroselinum crispum L.) seeds. The experiment was conducted under laboratory conditions. The number of germinated seeds, the shoot and root length of seedlings, vigor index and root and shoot length of the plant were measured. According to the morphological description of the colony and cells, five Bacillus bacteria (denoted as Bac4, Bac5, Bac6, Bac7, Bac8) were selected for further examination. All isolates showed good PGP potential. The isolates that stand out are isolates Bac5, Bac7 and Bac8. The best effect on the seed germination was exerted by B5 and Bac8 isolates. Isolates Bac7 and Bac8 had the greatest stimulatory effect on seedling and plant growth. Having great PGP traits, these isolates may represent a biological alternative for the application of harmful pesticides and chemical fertilizers in the production of summer savory and parsley.