High potential of cotton (Gossypium hirsutum L.) Bacillus isolates to promote plant growth

Abstract

Cotton is socially and economically important worldwide. Notably, research on eco-friendly technologies that increase the sustainability of this production system is increasing. We explored the potential of bacterial strains isolated from cotton roots to promote plant growth. Bacteria were isolated from cotton roots by using a pasteurization method and cultivated on nutrient agar for strain purification and selection. The bacterial strains were subjected to in vitro tests to verify their ability to solubilize calcium phosphate, producing indole-3-acid acetic, siderophores, and cellulase. Potential strains were selected for the in vivo experiments in a greenhouse with cotton cultivars FM 985 and TMG 47. Treatments were conducted using 1 mL (108 CFU/mL) of bacterial strain culture and a commercial inoculant, with nine replicates observed for 110 d. The plants were evaluated for physical, phytochemical, and macronutrient parameters. The physical parameters indicated a positive relationship between cultivars and microorganisms, increasing the height, fresh mass of the shoot, dry mass of fruits and roots, root volume and length, and number of leaves. Phytochemical parameters showed improvements in total sugars, ascorbate peroxidase, phenolic compounds, free amino acids, total sugar, chlorophyll A, reducing sugars, flavonoids, catalase, and chlorophyll B. In conclusion, our results showed that our bacterial isolates from cotton roots had many biochemical features related to plant growth promotion and were able to promote the growth of cotton cultivars in a greenhouse experiment. Future research could conduct field tests to evaluate their use for improving cotton productivity on a large scale.