Rizobactérias como estratégia de mitigação do estresse por déficit hídrico no gergelim BRS morena

Abstract

A potential strategy to improve water deficit tolerance in agricultural production systems is the application of plant growth-promoting bacteria. Rhizobacteria promote several benefits, such as inducing plant tolerance against abiotic stresses. Despite being considered tolerant to water deficit, sesame, a dicotyledonous, herbaceous species and one of the oldest oilseed plants used by humanity, requires well-distributed rainfall to reach its maximum productive potential. Although this characteristic represents an advantage for cultivation in semi-arid regions, drought is still a challenge for the cultivation of this plant by small and medium producers, especially in the Northeast region. Therefore, the objective of this work is to analyze the interaction of bacilli-based inoculants as a strategy to mitigate water deficit in sesame genotype. The experiment was carried out in a greenhouse at Embrapa Algodão (Campina Grande-PB) using the cultivar BRS Morena in pots with a capacity of 18 L. The experimental design was completely randomized, established by a random process in a 2 factorial scheme (water regime - daily irrigation and temporary suspension of irrigation) x 6 (sources of variation), totaling 12 treatments with 5 repetitions. The treatments were characterized in: (i) management with chemical nitrogen (ammonium sulfate, SAM; 21% N); and (ii) management with 4 bacilli-based inoculants (B. subtilis strain pant001, ESA 13, ESA 402 and M143). The following variables were evaluated: plant height, stem diameter, number of capsules, weight of 1000 seeds, shoot dry mass, root length, root dry mass, nitrogen and phosphorus content in leaves and physiological variables such as Ci , A, gs, E, A/E, A/ci,. In addition, analysis of the expression of DREB1 and SHDZ7 genes responsive to water stress, activities of antioxidant enzymes (Superoxide dismutase, Catalase and Ascorbate peroxidase), relative content of proline and photosynthetic pigments were performed. The experiment data were submitted to analysis of variance (P≤0.05), the means of treatments were compared by the Tukey test (P≤0.05) and the water conditions were compared by the Student's T test (P≤0.05). 05) The results showed a positive effect of inoculants for all agronomic and physiological variables. The analysis of nitrogen and phosphorus in leaves showed accumulation in the stressed treatments, with nitrogen and pant001. There was a significant effect for proline, superoxide dismutase, ascorbate peroxidase, catalase and photosynthetic pigments. Regarding gene expression, treatments inoculated with ESA 13, ESA 402 and with nitrogen were overexpressed. Considering the final production, the strains pant001 and M143 established a better interaction with increment of 24% and 21%, respectively, for the weight of a thousand seeds, when compared to the treatment without nitrogen, under water deficit. Therefore, with the results it was possible to identify the best genotype x inoculant interactions under water stress for treatments with strains pant001, M143 and ESA 402.