Actinomycetes Promote Growth in Nicotiana tabacum L. Seedlings

Abstract

Plant growth promoting bacteria (PGPB) are a viable option for sustainable agriculture and an eco-friendly alternative to the excessive use of chemical fertilizers and pesticides. Beneficial microorganisms of this type, such as actinobacteria, have the ability to promote plant growth. The study aims to evaluate the potential of two strains of actinomycetes Streptomyces sp. (EA2 and B8), as promoters of the initial growth of tobacco (Nicotiana tabacum L.) seedlings under controlled conditions. Beneficial characteristics such as indoleacetic acid (IAA) production, biological nitrogen fixation and phosphate solubilization were evaluated in vitro. A completely randomized experimental design was applied with two PGPB treatments: T1 (Streptomyces sp. EA2 + B8); T2 (Trichoderma harzianum), and T3 (Sterile distilled water) control treatment, with three replicates per treatment. The response variables studied in vivo were stem length (TL) and root length (RL), leaf width (W) and length (LH), and fresh and dry biomass of shoot and root parts. The results obtained reveal that strains EA2 and B8 possess BPCV characteristics, such as phosphate solubilization, IAA production and biological nitrogen fixation. T1 strains (EA2 + B8) had a positive ef fect on the evaluated growth indicators, outperforming T2 (T. harzianum) and the control treatment (T3). It is confirmed that the combination of Streptomyces sp strains (EA2 + B8) is an ef fective, safe, and eco-friendly alternative, with the with potential to reduce the application of agrochemicals in tobacco cultivation (N. tabacum L.).