Endophytic bacteria improve jute growth through induction of phytohormones-related gene expression

Plants coexist with complex populations of microorganisms, including Plant Growth-Promoting Rhizobacteria (PGPR). PGPR bacteria help in plant development by secreting numerous plan growth-promoting compounds like IAA, gibberellin, siderophore, and cytokinin. They also provide resistance to plants against different pathogens. Jute fibre is the second most important fibre next to cotton, obtained from the bark of plant through microbial retting process. Hence, increased plant growth means increased bark i.e., increased fibre. This study aims to identify the molecular, physiological and growth promotion characteristics of non-rhizobial bacterial specie from the surface-sterilized root of healthy and biotic stressed (nematode-infested) jute (Corchorus capsularis; Corchorus olitorius and an advanced variety of C. olitorius, Robi-1). We have identified 62 culturable bacterial isolates from healthy and nematode-infected jute plant using bacterial 16S rDNA sequencing. All the isolates were distributed to Bacillus, Staphylococcus and Ensifer genera, respectively. B. cereus, S. hominis and a consortium increased the growth phenotype (Root length, shoot length, germination rate, root and shoot biomass) of C. capsularis (CVL-1), C. olitorius (O-9897), and an advanced variety of C. olitorius (Robi-1), respectively. Increased expression (qRTPCR analysis) of growth hormones GA-20 and GA-03 oxidase corroborates plant growth induction by increased production of the growth hormone gibberellin. Taken together, our results suggest that plant-growth promotion by endophytic bacteria may involve the increased expression of growth hormone gibberellin and nutrient uptake. B. cereus and S. hominis having plant growth-promoting traits could be useful in sustainable agriculture practice.