Beneficial impact of multi-bacterial inoculation on growth of selected Brassicaceae seedlings in a greenhouse culture

Modern agriculture requires the development of new eco-friendly and cost efficient methods of crop production. In this study we tested if engineering Brassica microbiome by supplementation it with an inoculum composed of selected microorganisms can accelerate seedling growth and be a substitute for inorganic fertilizers. We hypothesised that the multiorganismal inoculum will be more efficient and affect a wide range of plants compared to inoculation with a single microorganism. We developed and examined several new multispecies inocula in the cultivation of different Brassica oleracea, B. rapa, Eruca sativa and Lactuca sativa cultivars. Every microorganism used for biotization was isolated from Arabidopsis arenosa (Brassicaceae) and tested for plant growth promoting properties. Of all the inocula tested, one (T4) containing only bacteria (Chryseobacterium lathyri, Bacillus cereus, Lysinibacillus fusiformis, Pseudomonas protegens) proved to be particularly efficient in increasing the fresh biomass of most B. oleracea and B. rapa cultivars cultured in the growth chamber. None of the bacteria used in the inoculum was able to activate plant growth individually. Thus, T4 inoculum was evaluated in a large-scale greenhouse culture of young Brassica vegetables. The results confirmed the positive effect of inoculation on the growth of selected Brassica crops, but it differed according to the plant genotype. What is more, the T4 inoculation proved to be as effective for increasing plant biomass as synthetic fertilizers. None of the inocula tested improved the growth of plants from genus other than Brassica.