Banca de DEFESA: RITA HILÁRIO DE CARVALHO

Ureide metabolism, growth and yield of common bean under co-inoculation with Bradyrhizobiumspp. and Azospirillum
brasilense

Plant growth;Phaseolus vulgaris;Rhizobium; FBN

The success of the practice of inoculating seeds with disease-fixing bacteria in common bean crops in the field can be affected by several factors. Co-inoculation with plant growth-promoting bacteria is estimated to assist in the establishment of BNF, ensuring improvements in plant nodulation, growth and productivity. The objective of this study was to evaluate the contribution of inoculation and co-inoculation of rhizobia and plant growth-promoting bacteria on common bean growth and productivity, as well as to quantify differentially expressed genes related to the transport of fixed N. Greenhouse experiments were controlled in autoclaved substrates, where nodulation, biomass, the proportion of ureides in the xylem sap, and the expression of genes linked to the transport of N in common bean were evaluated. Plants of the Pérola and Ouro Negro cultivars were inoculated with the CIAT 899 strain of Rhizobium tropici, and co-inoculated with the CPAC 7 strains of Bradyrhizobium diazoefficiens, and Abv-5 and Abv-6 of Azospirillum brasilense. The plants inoculated with R. tropici, and combined with A. brasilense and B. diazoefficiens, presented 49, 46 and 56%, respectively, of proportion of N-ureido exported in the xylem sap, while the plants that obtained mineral N reached 23%. Plants that received mineral N and that presented a higher proportion of amino acids in the xylem sap, higher expression of the permease gene, associated with the transport of N from the xylem to the stem. Controlled experiments were conducted under field conditions to evaluate the effect of co-inoculation of growth-promoting bacteria on common bean growth and obedience. The experiments were carried out in Ponta Grossa-PR and Seropédica-RJ, using strains of R. tropici, B. diazoefficiens, B. japonicum, A. baldaniorum and A. brasilense, with different doses of inoculants containing Bradyrhizobium sp., with cultivars of carioca and black beans. The plants were collected for biomass evaluation, and in the evolution of grains for productivity evaluation. The high native population of rhizobia in the areas, reflected in good results of biomass and conducts in treatments that did not receive inoculation or fertilization with N, with productivity of 2500 kg ha-1 in Ponta Grossa and 1900 kg ha-1 in Seropédica. A meta-analysis was conducted to identify factors related to the efficiency of rhizobia inoculants on common bean crop productivity. Published and unpublished works were gathered, with results of controlled experiments under field conditions in Brazil between 2000 and 2021. The data obtained were recorded in a spreadsheet for analysis in an R environment, on biomass and crop productivity. The inoculation of fixative bacteria promoted a 22% increase in productivity when compared to the control treatment. Cultivations inoculated with N-fixing plants can reach productivity above 2000 kg ha-1.