Daucus carota L. Seed Inoculation with a Consortium of Bacteria Improves Plant Growth, Soil Fertility Status and Microbial Community

Featured Application We analyzed the production of different auxins and the presence of the ability to solubilize phos-phates and the 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme in a consortium of four bacteria. The consortium was inoculated in an open field experiment on carrots, with very positive impacts on the development of the plant and on the soil microbial community. The present work aimed to study suitability of a consortium of Azospirillum brasilense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, and Burkholderia ambifaria as biofertilizers. Strains were assayed for plant growth-promoting characteristics (i.e., auxins production, phosphate solubilizing capability, and 1-aminocyclopropane-1-carboxylate deaminase activity). The consortium of four bacteria was then inoculated on carrot seeds and tested in an open field experiment. During the open field experiment, plant growth (morphological parameters, chlorophylls, and carotenoids), soil chemical analysis, and molecular and physiological profiles of soils were investigated. Each strain produced different amounts of indole-3acetic acid and several indole-derivates molecules. All strains showed phosphate solubilization capability, while 1-aminocyclopropane-1-carboxylate deaminase activity was only detected in H. seropedicae and B. ambifaria. The bacterial consortium of the four strains gave interesting results in the open field cultivation of carrot. Plant development was positively affected by the presence of the consortium, as was soil fertility and microbial community structure and diversity. The present work allowed for deepening our knowledge on four bacteria, already known for years for having several interesting characteristics, but whose interactions were almost unknown, particularly in view of their use as a consortium in a valid fertilization strategy, in substitution of agrochemicals for a sustainable agriculture.

Automated summary

The study focused on analyzing the application of a consortium of four bacteria in open field cultivation of carrots, demonstrating their positive impacts on plant growth and soil microbial community. Each strain in the consortium showed different characteristics in promoting plant growth and phosphate solubilization, with positive effects observed on plant development and soil fertility. The research deepened our understanding of these bacteria and highlighted their potential for sustainable agriculture as biofertilizers.