Biopriming of maize seeds with plant growth-promoting bacteria isolated from the earthworm Aporrectodea molleri: effect on seed germination and seedling growth.

Earthworms have become a potential source of multi-beneficial bacteria and effective bioinoculants. Seed biopriming is an efficient inoculation method to apply bacteria prior to sowing, which enhances the chances of bacterial candidates to colonize the rhizosphere and/or establish a liaison with the plant. In this study, we evaluated plant growth-promoting traits of bacterial strains isolated from the earthworm's Aporrectodea molleri chloragogenous tissue. In addition, we investigated their prospective use as biopriming agents to enhance Zea mays germination and seedling growth. Results were subjected to principal component analysis for potential correlations between the studied parameters. The bacterial strains displayed different in vitro plant growth-promoting characteristics and were efficient when applied in vivo as they significantly increased maize germination rate (26-78%), root elongation (67-84%), seedlings fresh weight and dry weight. Aeromonas encheleia TC22 was the most significant strain to influence germination due to its high ability to produce indole-3-acetic acid, and along with Pseudomonas azotoformans TC1, they were the most proficient at enhancing seedling root elongation and biomass, which was significantly correlated with their in vitro plant growth-promoting traits. Our findings indicate that isolates TC22 and TC1 are potent bio-primers for maize seeds and should be tested further for their use as biopriming inoculants.