Plant Growth-Promoting Effects of Bacterial Isolates Obtained from Funneliformis mosseae Spores on Tomato (Solanum lycopersicum L.) Seed Germination and Early Plant Development

Bacterial isolates obtained from spores of the arbuscular mycorrhizal fungi (AMF) have been reported to possess various plant growth-promoting traits. These bacterial isolates enhance plant growth and development through mechanisms such as phytohormone production and nutrient mobilization. The objective of this study was to investigate the ability of bacterial isolates to promote plant development. Five bacterial isolates, Bacillus methylotrophicus, Fictibacillus barbaricus, Stutzerimonas stutzeri, Bacillus aryabhattai, and Priestia aryabhattai, were isolated from AMF (Funneliformis mosseae) spores. The results indicated that all five bacterial isolates promoted plant growth. The greatest positive effects on the tomato seed germination were obtained with Bacillus methylotrophicus and Stutzerimonas stutzeri, with germination percentages of 90% and 95%, respectively. In addition, Stutzerimonas stutzeri enhanced early tomato seedling growth. Priestia aryabhattai produced the highest amount of indole-3-acetic acid (IAA) at 94.43 µg mL−1, which is the auxin phytohormone for plant growth promotion. Furthermore, Bacillus methylotrophicus, Fictibacillus barbaricus, and Bacillus aryabhattai were able to produce high levels of ammonia, which may contribute to improving plant growth in nutrient-deficient environments. In addition, Bacillus methylotrophicus, Bacillus aryabhattai, and Priestia aryabhattai were able to solubilize both phosphate and potassium. These findings suggest that the investigated bacterial strains could be combined with AMF to improve crop establishment and support sustainable agricultural systems by enhancing nutrient availability and reducing dependence on chemical fertilizers.