Screening of Sunflower Hybrids Using Physiological and Agronomic Traits

Researching the photosynthetic activity of sunflower (Helianthus annuus L.) is essential for understanding how different genotypes respond to environmental conditions and utilise solar energy for growth and productivity. The objective of this study was to gain insight into and quantify the adaptation of ten sunflower hybrids during the flowering stage under field conditions. As part of an ongoing sunflower breeding programme, this research aimed to assess genotypic differences in photosynthetic performance and yield-related traits in response to variable environmental conditions. During the flowering stage, chlorophyll a fluorescence (ChlF) parameters revealed significant genotypic differences in energy fluxes, particularly in ABS/RC, DI0/RC, ET0/RC, and RE0/RC. Those results indicate variability in light-harvesting efficiency and electron transport capacity. Although specific photochemical efficiency indicators (e.g., TR0/RC, TR0/ABS, ET0/TR0) showed slight variation, energy dissipation and photosystem I-related parameters differed significantly among hybrids. Leaf temperature and chlorophyll content also varied and showed moderate correlations with fluorescence-based indicators. Yield components (plant height, head diameter, and seed mass per head) displayed significant differences among sunflower hybrids, with notable opposite patterns between plant height and head size. Revealed strong relationships between photosynthetic performance (PITOTAL, RE0/ABS) and yield traits, particularly plant height and number of seeds per head, were confirmed with correlation analysis. Principal Component Analysis (PCA) distinguished the hybrids into distinct groups. The analysis confirmed physiological and morphological variability among hybrids, enabling effective screening of genotypes for breeding purposes. Photosynthesis is a key physiological trait that directly influences biomass accumulation and seed yield, making it a critical parameter in evaluating the performance and adaptability of various sunflower genotypes. Thus, this study demonstrates the integrative value of combining ChlF, thermal, and agronomic traits for identifying high-performing sunflower hybrids under optimal field conditions.