Improvement of growth -physiological traits of hazelnuts provenances inoculated with growth promoting bacteria under field conditions

The slow growth of hazelnut seedlings, particularly during the initial years of afforestation, hampers the rehabilitation and development programs of hazelnut forests. In this context, biological fertilizers, especially plant growth-promoting bacteria, can be an effective strategy to enhance the growth and physiological traits of hazelnut seedlings. In May 2017, new hazelnut potted seedlings from two seed sources - Fandoglou (Ardabil Fandoglou forest) and Makesh (Aghvalar Guilan forest) - were propagated in an Ardabil hazelnut nursery. These seedlings were inoculated separately and in combination with Pseudomonas putida DSM291, Bacillus subtilis FzB24, and Enterobacter cloacae E1. In November 2017, the one-year-old hazelnut seedlings were transferred to agricultural lands bordering the Fandoglou forest. The seedlings were planted in rain-fed conditions following a randomized complete block design with three replications of 12 based on two factors: fertilization and seed origin. After four years, it was observed that inoculated seedlings from both origins outperformed non-inoculated ones in all investigated traits. The largest parameters of the studied variables were attributed to the Fandoglou-origin seedlings inoculated with a combination of three bacteria. These seedlings showed a survival rate of 49.7%, collar diameter growth of 51.1%, height growth of 60.4%, and dry mass increases in roots (85.6%), stems (75.1%), and leaves (68.2%). Additionally, photosynthesis increased by 49.9%, stomatal conductance by 58.04%, water consumption efficiency by 121.7%, and chlorophyll content by 46% compared to non-fertilized Fandoglou-origin seedlings. In conclusion, considering the role of the studied growth-promoting bacteria (especially the combined treatment) in enhancing the growth characteristics and physiology of hazelnut provenances, inoculating hazelnut seedlings with bacteria in nurseries can be a beneficial strategy for successful field transplantation.