Search

Environmental conditions throughout the sunflower life cycle affect its phenological and physiological aspects, influencing growth and development, and ultimately, grain yield and oil content. While numerous studies have clarified the effects of specific environmental factors on sunflower oil yield and its components, a comprehensive understanding of how combined environmental conditions influence sunflower productivity requires research conducted under real production conditions. Given that different sowing dates expose the crop to varying environmental conditions, this study investigated the effects of three contrasting sowing dates and the underlying environmental conditions on sunflower grain yield, oil content, and oil yield. A broad set of commercial hybrids was evaluated using a randomized complete block design with four replicates across five environments (year or geographic location) in central Argentina. The sowing date was the major source of variation in grain yield, oil content, and oil yield, accounting for 57.2, 62.9 and 62.6% of the total variation, respectively. Sunflowers sown in early spring exhibited significantly higher grain yield and oil content compared to those sown in late spring or early summer, which resulted in 22.3 and 39.1% lower grain yield and 2.6 and 11.3% lower oil content, respectively. Solar radiation and the photothermal coefficient during grain filling were the major environmental factors influencing sunflower parameters. Surprisingly, genotype and its interactions accounted for less than 2.7% of the variation in sunflower oil yield. This study enhances our understanding of how integrated environmental factors impact sunflower grain yield, oil content, and total oil yield.

Abstract The increased incidence of extreme temperature events due to global climate change poses a major challenge for crop production. Ability to increase temperature tolerance through genetic improvement requires understanding of how crops and their wild relatives respond to extreme temperatures. We developed a high-throughput technique to evaluate tolerance to freezing stress (FS) and heat stress (HS) in wild, crop–wild hybrid and cultivated sunflower (Helianthus annuus L.). We also investigated whether trade-offs exist between stress tolerance and growth under benign conditions. Eleven experiments were performed under a combination of growth-chamber and field conditions. In growth-chamber experiments, FS and HS consisted of exposing acclimated plants at the 2–4-leaf stage to temperatures ranging from to –2.5°C to –4°C for 2–4 h and from 52°C to 54°C for 2–3 h. In the field, plants were grown for 32 days during midwinter (FS: average Tmean = 9.9°C and Tmin = 3.8°C) or for 10 days in a heat tent (HS: average Tmean = 30.1°C and Tmax = 43.3°C). We observed large differences in tolerance to FS and HS between wild and cultivated sunflower. Wild sunflower showed higher FS tolerance than cultivated in both growth-chamber and field experiments, whereas cultivated sunflower showed higher HS tolerance in growth-chamber experiments. No differences in HS tolerance were observed in the field. Crop–wild hybrids generally showed intermediate HS and FS tolerance. We found no evidence of a growth-tolerance trade-off, which suggests that tolerance might be introgressed into elite germplasm without growth penalties. The study reveals that wide genetic variation for the tolerance to extreme temperatures exists in the primary gene pool of sunflower.