Beneficial properties of soil bacteria from Cannabis sativa L.: Seed germination, phosphorus solubilization and mycelial growth inhibition of Fusarium sp.

Abstract

Soil microbes play a vital role in promoting plant growth and health through various mechanisms, including nutrient availability, microbial competition inhibition, and plant defense. However, their interaction and effects in cannabis cultivation remains largely unexplored. In this study, we investigated the symbiotic effects of soil bacteria on cannabis by characterizing microbial communities from soil samples collected in the Salado-Ibague (S) and Mariquita (M) regions of central west Colombia. Among the 265 microorganisms detected, we selected 21 g-positive bacteria from S and 10 g-positive bacteria from M for further analysis. The cannabis seed germination rates were evaluated after eight months of storage and seed pretreatment to assess the potential benefits of these soil bacteria. Remarkably, seed germination rates exceeding 80% were exhibited by 10 Bacilli strains, highlighting their ability to maintain germination potential even under storage and pretreatment conditions. In addition, antagonism assays were conducted to investigate the inhibitory effects of Bacilli on the mycelial growth of the pathogen Fusarium oxysporum (MGIF). Significant inhibition of mycelial growth was observed in nine Bacillus strains. Among them, Bacillus S11 exhibited the most significant inhibition (MGIF: 65%) compared to the control F. oxysporum (MGIF: 0%) (n = 3, p < 0.05). Additionally, the phosphorus solubilization capacity of cannabis soil Bacilli was examined using the phosphorus solubilization index (PSI). Among 31 Bacilli evaluated, six significantly increased the bioavailability of non-useable tricalcium phosphate into a useable form of monophosphate (PSI: 247–435). Our study has unveiled several beneficial characteristics of Bacillus strains isolated from cannabis soil. These include maintaining seed germination rates even after extended storage and pretreatment, exhibiting phosphorus solubilization capabilities, and demonstrating inhibitory effects against the microbial pathogen F. oxysporum. These findings emphasize the potential of harnessing the beneficial properties of Bacilli for sustainable cannabis cultivation practices.