CRESCIMENTO INICIAL DE HÍBRIDOS DE GIRASSOL TRATADOS COM BIOINSUMOS E REGULADOR DE CRESCIMENTO SOB RESTRIÇÃO HÍDRICA

Abstract

Sunflower (Helianthus annuus L.) is a crop of significant economic importance, especially as a second crop alternative in Brazil. However, water deficit during the initial cycle can compromise plant establishment and performance, making it necessary to adopt strategies that increase stress tolerance. In this context, the use of bio-inputs and growth regulators in seed treatment has been considered a promising alternative. Thus, the present study aimed to evaluate the response of five sunflower hybrids subjected to water deficit and treated with growth-promoting microorganisms and plant regulators. The experiment was conducted in a randomized block design, in a factorial scheme 5 x 8, involving five hybrids and different seed treatments based on Trichoderma asperellum, T. harzianum, Bacillus amyloliquefaciens, growth regulator, and their combinations. After imposing water stress, the variables emergence, plant height, stem diameter, root length, and number of leaf pairs were evaluated. The results indicated a significant effect of the hybrids and treatments on most of the variables analyzed, as well as interaction between the factors for characteristics related to initial growth. In general, the H260, T204, and H250 hybrids showed better agronomic performance, standing out mainly in terms of root development and stem diameter. Treatments containing isolated microorganisms or associated with the growth regulator promoted increases in emergence, height, and root length, showing potential for mitigating the effects of water stress. However, certain combinations did not result in a positive response, indicating that the efficiency of the treatments depends on the compatibility between the genotype and the bioinput used. It is concluded that the genetic component has a decisive influence on the response to water deficit, but the treatment of seeds with growth-promoting microorganisms can contribute to better initial crop establishment. The adoption of these technologies, associated with the appropriate choice of hybrid, represents a viable strategy to increase the resilience of sunflowers under water-limited conditions.