RESPOSTA DE HÍBRIDOS DE GIRASSOL SUBMETIDOS AO DÉFICIT HÍDRICO E AO TRATAMENTO DE SEMENTES COM BIOINSUMOS

Abstract

Sunflower is a crop of great economic and environmental importance, especially in Brazil, where it is cultivated as an alternative for the second growing season. Its production has been increasing nationwide, with the state of Goiás being the largest producer in the country. However, climatic adversities have been a major issue, affecting the crop’s productivity. The objective of this study was to evaluate the tolerance of five sunflower hybrids to water deficit. The experiment was conducted in the field at the Federal Institute of Goiás, Urutaí Campus. The experimental design used was a randomized block design, with treatments arranged in a 5 x 5 factorial scheme and four replications. The first factor corresponded to sunflower hybrids (H250, H251, H260, T204 CL, and T203), subjected to seed treatments with Trichoderma asperellum, T. harzianum, a growth regulator (cytokinin + gibberellin + indoleacetic acid), T. asperellum + growth regulator, and T. harzianum + growth regulator. The recommended rate of the commercial product per hectare (c.p./ha) was applied for each 1000 g of seeds, adjusting the product quantity to the seed mass of each replication. After the imposition of water deficit, germination percentage at seven days after sowing (%), plant height (cm), number of leaf pairs, stem diameter (cm), and root length (cm) were evaluated. Germination percentage, plant height, and root length were influenced by both hybrid and seed treatment. Hybrids H251, H260, and T204 showed the best overall performance. The combinations T. harzianum + growth regulator and T. asperellum + growth regulator promoted higher germination, while treatments with isolated microorganisms and T. harzianum + growth regulator favored plant height and root development. The number of leaf pairs varied only among hybrids, with H250 and H260 standing out. A significant interaction was observed for stem diameter. In general, T. asperellum and T. harzianum stimulated growth under water deficit conditions, but the combination T. asperellum + growth regulator showed incompatibility.