Assessment of Germinability of Sorghum (Sorghum bicolor) Seeds Treated in Inoculums and Metabolites of Growth Promoting Rhizobacteria

The rapid rise in human population has led to increased use of agrochemicals in agriculture, negatively impacting the environment. This study assessed the potential of plant growth-promoting rhizobacteria (PGPR) in enhancement of germinability of sorghum seedlings. For the study, 15 rhizobacterial inoculums and metabolites were used. The inoculums and metabolites were applied both as seed and soil treatments. The seeds were then monitored for germination, plant height and vigor index over 20 d. The results showed that in the inoculum treatments, isolates, such as Providencia rettgeri, Serratia liquefaciens, and Bacillus. cereus significantly enhanced the vigor index of the sorghum seedlings, when compared to the control. However, other strains showed no significant improvement in germination and vigor index of the sorghum seedlings. For the soil treatments, certain strains like Serratia liquefaciens and Providencia rettgeri showed higher vigor index values in the sorghum seedlings while others, such as Bacillus thuringiensis and Bacillus cereus, demonstrated lower values. Generally, the germination rates generally did not differ significantly between the control and treated seeds. In the case of the metabolite treatments, varying impacts on vigor index and germination rates of the seedlings were observed, with some significantly enhancing plant growth while others did not. The study concludes that specific strains of PGPR and their metabolites can positively impact sorghum growth, suggesting that targeted use of beneficial microbes could reduce the reliance on agrochemicals. The study however posits that the variability in results highlights the need for further studies on optimization of application methods and formulations of the inoculums and metabolites for improved germinability of sorghum seedlings.