Strategies of co-inoculation with plant growth-promoting bacteria in soybean: Effects on nutrition, physiology, growth, and grain yield

• Grant number: 25/00914-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2025
• End date: March 31, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Fernando Shintate Galindo
• Grantee: Hugo Rocha Silva
• Host Institution: Faculdade de Ciências Agrárias e Tecnológicas. Universidade Estadual Paulista (UNESP). Campus de Dracena. Dracena , SP, Brazil

Abstract

The use of plant growth-promoting bacteria (PGPB) has been increasingly adopted, particularly under tropical conditions, as they offer significant benefits for soybean growth and development, ultimately enhancing grain yield. Considering the advantages observed in various crops through PGPB inoculation, primarily due to their phytohormonal effects that directly promote plant growth, root system development, and, consequently, improved water and nutrient uptake and utilization, co-inoculation with Bradyrhizobium sp. and PGPB, such as Azospirillum brasilense, Bacillus aryabhattai, and more recently Methylobacterium symbioticum, is believed to enhance crop development and, in turn, grain yield. Additionally, PGPB co-inoculation can boost biological nitrogen fixation (BNF) and improve the solubilization and efficiency of nutrient use from fertilizers. This study aims to evaluate the effects of co-inoculations with plant growth-promoting bacteria on the nutrition, physiology, growth, and productivity of soybeans. The research will be conducted in the municipality of Dracena, São Paulo, Brazil, on a typical Oxisol with sandy texture. The experiment will follow a randomized block design with four replicates and eight treatments: (1) control - inoculation with Bradyrhizobium sp. only, without co-inoculations; (2) inoculation with Bradyrhizobium sp. + A. brasilense; (3) inoculation with Bradyrhizobium sp. + Bacillus aryabhattai; (4) inoculation with Bradyrhizobium sp. + Methylobacterium symbioticum; (5) Bradyrhizobium sp. + A. brasilense + B. aryabhattai; (6) Bradyrhizobium sp. + A. brasilense + M. symbioticum; (7) Bradyrhizobium sp. + B. aryabhattai + M. symbioticum; (8) Bradyrhizobium sp. + A. brasilense + B. aryabhattai + M. symbioticum. All treatments will involve seed inoculation, except for M. symbioticum, which will be applied via foliar spraying at the V6 growth stage (five fully developed trifoliolate leaves on the main stem). Leaf chlorophyll index (ICF), gas exchange parameters (IRGA), shoot and root dry mass at full flowering (R2) and shoot dry mass, production components and grain yield at the end of the cycle (R8), as well as N accumulation in shoots and grains will be evaluated.