Gas exchange, water relations, and growth of Brachiaria brizantha cv. Marandu and Brachiaria hybrid Mavuno pastures inoculated with Azospirillum brasilense and Pseudomonas fluorescens under warming on field conditions

• Grant number: 24/22003-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2025
• End date: January 31, 2027
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Carlos Alberto Martinez y Huaman
• Grantee: Ramon Martins Santana
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 22/15021-2 - Physiological and productive performance of forages Brachiaria brizantha cv Marandu and the hybrid Brachiaria Mavuno inoculated with Azospirillum brasilense and subjected to warming in a future climate simulation experiment, AP.PFPMCG.R

Abstract

The sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC) recently warned of the inevitability of increasing global average temperature. This temperature increase will lead to climate change with direct impacts on countries whose economies are focused on agriculture, such as Brazil. Brazil is one of the world's largest beef producers, producing mainly through pastures in a rainfed system. Therefore, studies investigating the physiology of forage species under future temperature conditions are of utter importance for the maintenance and adaptation of these crops in the face of the current scenario and future climate change scenarios. The present project aims to determine the effects of increased temperature (+2°C) under field conditions on the photosynthetic dynamics, water relations, and growth of Brachiaria brizantha cv. Marandu and Brachiaria híbrida cv. Mavuno inoculated or not with Azospirillum brasilense and Pseudomonas fluorescens, a nitrogen-fixing and a plant growth-promoting bacteria, respectively, that can be used to increase pasture productivity and improve their resistance to abiotic stresses. Foliar gas exchange, relative water content, xylem water potential, foliar and root proline accumulation, and biomass production of both cultivars will be evaluated. The present study hypothesizes that the increase in temperature will increase the transpiration rate and stomatal conductance of both cultivars, reducing their water status, especially during the dry season. Inoculation with A. brasilense and P. fluorescens will mitigate the negative effects of elevated temperature by promoting greater root development, allowing both cultivars to meet their water needs by exploring deeper soil layers and increasing their biomass production. It is also expected that during periods of drought, inoculated plants will be less affected by water stress than non-inoculated plants. (AU)