Characterization of a multifunctional inoculant product based on methylotrophic bacteria and its effect on plant-growth promotion and plant-induced resistance

Abstract

Natural agricultural products based on microorganisms have been increasingly used as sustainable alternatives to agrochemicals. The Pink Pigmented Facultative Methylotrophs (PPFMs) have been widely explored and can benefit plants in many ways, such as producing phytohormones or acting as biostimulants or biofertilizers by providing nutrients. Some species of PPFMs can also improve plant defense against phytopathogens through the production of antimicrobial compounds or molecules capable of activating the plant immune system. The scientific feasibility demonstrating the different effects of bacterial inoculants in promoting growth and inducing resistance in plants was clearly demonstrated in Phase 1. In the current phase of the Project, the focus is to explore the best conditions for the formulation and application of the product and testing its efficiency in plants under field conditions. Along with an improved biochemical and molecular characterization of the bacterial isolates, different culture media, growth conditions and forms of application will be tested to guarantee the availability of the product to plants in a more efficient and sustainable way. The product in its most effective formulation will be applied to soybean plants to evaluate its biostimulant, biofertilizer and defense-inducing action against phytopathogens, under controlled and field conditions. The parameters of shoot height, root dry mass and length, grain weight, and micro and macronutrient content will be evaluated in the analysis of soybean growth promotion. The induction of resistance will be verified through the analysis of defense gene expression by qPCR and evaluation of symptoms of black spot in tomato, and Asian rust, cercosporiosis, brown spot, target spot, powdery mildew, and anthracnose in soybean plants under field conditions. The proposed evaluations are essential for the registration of a good quality biofertilizer/biopesticide with MAPA, and to allow the understanding of the product´s mode of action on plants under natural conditions. Since we verified that the bacterial isolates were able to benefit plant growth and defense under controlled greenhouse conditions in Phase 1, we hope that these same methylotrophic bacteria, in a suitable formulation, can also favor the plants under natural field conditions. (AU)