Plant microbe mediated enhancement in growth and yield of canola (Brassica napus L.) plant through auxin production and increased nutrient acquisition

Purpose Application of beneficial microbes such as plant growth promoting rhizobacteria (PGPR) and endophytic fungi as bio-fertilizer may act as a substitute to minimize the utilization of chemical fertilizers, which often cause negative impacts on environment. In this regard, bio-fertilizer resurged as an alternate and eco-friendly technique for sustainable agriculture to improve crop growth and yield by the introduction of beneficial microorganisms in soil. Therefore, this experiment was designed to investigate whether the following microbial candidates, i.e., Enterobacter sp., Bacillus sp., and Piriformospora indica have the ability to influence growth of canola through uptake of nutrient and production of growth hormone. Materials and methods A pot experiment with three beneficial microorganisms such as Enterobacter sp., Bacillus sp., and a root endophytic fungus, P. indica, was conducted on two cultivars of canola (DGL and Punjab canola). The bacterial strain of Enterobacter sp. MN17 and Bacillus sp. MN54 (10(8) bacteria per seed) were applied individually as well as along with fungal strain (P. indica), and their impact was assessed against an uninoculated control treatment under normal soil condition. Results and discussion Results depicted that application of Enterobacter sp. MN17 and Bacillus sp. MN54 with P. indica significantly increased growth, physiological attributes, nutrient uptake, and soil microbiological attributes of canola. In particular, treatment MN54 + P. indica showed highest improvement in shoot biomass, stem diameter, and root length 100%, 65%, and 50% respectively in var. DGL, while increase in number of pods per plant was also recorded for treatment MN17 + P. indica and MN54 + P. indica for DGL (63%) and Punjab Canola (73%), respectively, as compared to control plants. The combined inoculation also increased root or/and shoot nutrient uptake and enhanced plant auxin pool. Therefore, colonization of P. indica and microbial strain, especially Bacillus sp., improves plant health by enhancing root proliferation because of upregulation of auxin producing genes and release of organic acids, respectively, which leads to better nutrient uptake and eventually enhanced crop growth. Conclusion Our results proposed that inoculation of Bacillus sp. MN54 with P. indica could be exploited to increase crop growth and seed yield through enhanced nutrient uptake and production of plant growth hormones.