Potencial biotecnológico de bactérias promotoras de crescimento e metabólitos microbianos na cultura da soja

Author(s)

Luiz Gustavo Moretti de Souza

• Document type: Doctoral Thesis
• Press: Botucatu. 2021-02-08.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agronômicas. Botucatu
• Defense date: 2020-12-11
• Advisor: Carlos Alexandre Costa Crusciol

Abstract

The adoption of sustainable production systems has increased considerably in recent years, driven mainly by societal demand for the production of high-quality food under low environmental impact. For soybean (Glycine max [L.] Merrill), a broad range of beneficial effects of bacteria have been reported, including biological nitrogen fixation (BNF), plant pathogen biocontrol, plant growth development, and the production of compounds such as lipochitooligosaccharides (LCOs), which activate several physiological and biochemical mechanisms. Rhizobial inoculants and plant growth-promoting bacteria (PGPB) have been widely applied as biofertilizers to legume crops, but plant responses to consortia of other beneficial microbes and microbial molecules have not been comprehensively explored. Therefore, in this study we evaluated the effects of co-inoculating N2-fixing Bradyrhizobium japonicum (strain SEMIA 5079) and Bradyrhizobium diazoefficiens (strain SEMIA 5080) with or without foliar application of plant growth-promoting Azospirillum brasilense (strains Ab-V5 and Ab-V6) and the biocontrol agent Bacillus subtilis (strain QST 713) and seed treatment with microbial secondary metabolites (MSM, rhizobial metabolites enriched in LCOs) on soybean. Experiments were conducted during two growing seasons under greenhouse conditions and three growing seasons under tropical field conditions with a short dry spell at the Lageado Experimental Farm of São Paulo State University (UNESP), Botucatu, São Paulo State, Brazil. We evaluated root system development (directly by optical reading and indirectly by applying rubidium nitrate, 85RbNO3), nutritional status, N-ureides, photosynthetic pigments, gas exchange parameters, antioxidant enzyme activities, proline, nodulation, plant growth development, agronomic efficiency index, and soybean grain yield and quality. Combining the beneficial bacterial consortium comprising Bradyrhizobium spp. and A. brasilense strains with MSM application helped alleviate soybean water stress under field conditions, promoting nodulation, N-ureide content, root and shoot development, photosynthetic activity, the production of photoassimilates and, ultimately, grain filling. Taken together, the results suggest that this combination is an important biotechnological strategy to achieve sustainable food production and security. (AU)

• FAPESP's process: 16/23699-8 - Management and coinoculation of microorganisms (Bradyrhizobium japonicum, Azospirillum brasilense, Bacillus subtilis and microbial metabolites) in soybean culture
• Grantee: Luiz Gustavo Moretti de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate