Effects of pesticide seed treatments on seed yield and oil quality of sunflower (Helianthus annuus L.)

Sunflower (Helianthus annuus L.) is a major oilseed crop, and systemic seed-applied pesticides are widely used to protect seedlings from early-season pests and diseases. However, their combined effects on agronomic performance and oil quality remain insufficiently understood. This study evaluated the effects of metalaxyl-M, thiamethoxam, and clothianidin on sunflower morphological traits, yield components, and seed fatty acid composition under field conditions during two consecutive growing seasons (2021–2022) in western Türkiye. The Sanbro MR hybrid was used, with untreated seeds serving as the control. Morphological and yield traits were analysed using analysis of variance, and principal component analysis (PCA) was conducted to explore relationships among treatments and traits. Fatty acid composition was determined to assess potential impacts on oil quality. Significant effects of year, treatment, and their interaction were detected for several traits, indicating that environmental conditions strongly influenced plant responses.In 2021, neonicotinoids, particularly thiamethoxam and clothianidin, were associated with increased plant height, head weight, and single-plant yield. In contrast, in 2022, metalaxyl-M was more strongly linked to increases in plant height and thousand-seed weight, suggesting improved seed filling. PCA results indicated that different active ingredients were associated with distinct trait groups. Seed treatments also caused significant, treatment-specific changes in fatty acid composition. Thiamethoxam promoted a shift toward a higher oleic acid profile, while metalaxyl-M was associated with increased saturated fatty acids, particularly stearic acid. Overall, these findings demonstrate that systemic seed treatments influence both agronomic performance and oil quality, emphasizing the importance of considering biochemical responses alongside yield in sunflower production.