ORIGINAL ARTICLE Biopriming of maize seeds with plant growth-promoting bacteria isolated from the earthworm Aporrectodea molleri: effect on seed germination and seedling growth S. Houida 1,2 , L. Yakkou 1,2 , L.O. Kaya 2 , S. Bilen 2 , M. Fadil 3 , M. Raouane 1 , A. El Harti 1 and S. Amghar 1 1 Research Team “Lumbricidae, Improving Soil Productivity and Environment (LAPSE)”, Centre: Eau, Resources Naturelles, Environnement et D´ eveloppement Durable (CERNE2D), Ecole Normale Sup ´ erieure (ENS), Mohammed V University, Rabat, Morocco 2 Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Atat ¨ urk University, Erzurum, Turkey 3 Physico-Chemical Laboratory of Inorganic and Organic Materials, Materials Science Center (MSC), Ecole Normale Sup ´ erieure, Mohammed V University in Rabat, Rabat, Morocco Significance and Impact of the Study: Earthworms harbour interesting bacteria that exhibit multiple beneficial plant growth-promoting (PGP) traits and could be applied as bioinoculants to enhance crop production. However, the bacteria–plant connection is rarely successful in field application. Bacteria iso- lated from the chloragogenous tissue of the earthworm Aporrectodea molleri were able to solubilize phosphate and potassium and produce the phytohormone indole-3-acetic acid, ammonium and nitrate. Zea mays seeds inoculated before sowing with those bacteria significantly increased the germination rate, seedlings’ root elongation and biomass compared with the control. Our results demonstrate the potential use of our strains as biopriming agents for maize seeds. Keywords earthworms, multi-beneficial bacteria, plant growth promotion, seeds biopriming, Zea mays. Correspondence Sofia Houida, Ecole Normale Sup ´ erieure (ENS), Mohammed V University in Rabat, Rabat 5118 Morocco. E-mail: sofia_houida@um5.ac.ma 2022/0072: received 10 February 2022, and accepted 7 March 2022 doi:10.1111/lam.13693 Abstract 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. Letters in Applied Microbiology 75, 61--69 © 2022 The Society for Applied Microbiology 61 Letters in Applied Microbiology ISSN 0266-8254 Downloaded from https://academic.oup.com/lambio/article/75/1/61/6989389 by guest on 19 January 2023