Effect of Planting Dates on Growth Traits of Sunflower Genotypes and Their Selected Lines

Abstract

A field experiment was conducted during the spring and autumn seasons of 2025 to cultivate sunflower (Helianthus annuus L.) at the fields of Al-Mussaib Technical College, Babil Governorate / Al-Mussaib Project area, located about 40 km north of the governorate (longitude 44.50, latitude 32.50). The study aimed to investigate the effect of planting dates on growth traits of sunflower genotypes and their selected lines.The experiment included two factors: the first factor was six sunflower genotypes, and the second factor was three planting dates. The experiment was laid out according to a Randomized Complete Block Design (RCBD) in a factorial arrangement.The results of statistical analysis showed significant differences among genotypes. The genotype Selected Zahra Al-Iraq recorded the highest mean plant height (176.00 cm), whereas the genotype Shamos recorded the lowest mean (156.33 cm). Planting dates had a significant effect, as the first planting date (20 June) gave the highest mean plant height (170.89 cm) compared with the third planting date (10 July), which gave the lowest mean (159.33 cm). The interaction treatment Selected Zahra Al-Iraq × first planting date recorded the highest value (181.00 cm), while Shamos × third planting date gave the lowest value (148.00 cm).For leaf area, significant differences were observed among genotypes. The genotype Selected Shamos achieved the highest mean leaf area (0.845 m²), whereas Zahra Al-Iraq recorded the lowest mean (0.535 m²). The first planting date (20 June) produced the highest mean leaf area (0.707 m²), while the third planting date (10 July) resulted in the lowest mean (0.671 m²). The interaction Selected Shamos × third planting date recorded the highest value (0.856 m²), whereas Zahra Al-Iraq × second planting date recorded the lowest value (0.474 m²).Significant differences among genotypes were also found for the leaf area index (LAI). The genotype Selected Zahra Al-Iraq recorded the highest mean (6.4842), while Shamos recorded the lowest mean (3.8596). The first planting date (20 June) resulted in the highest mean LAI (4.9384), compared with the third planting date (10 July), which gave the lowest mean (4.7768). The interaction Selected Zahra Al-Iraq × second planting date recorded the highest LAI (7.4600), whereas Shamos × second planting date recorded the lowest value (3.6010).Regarding head area, significant differences among genotypes were observed. The genotype Selected Argensun recorded the highest mean head area (383.57 cm²), while Zahra Al-Iraq recorded the lowest mean (323.33 cm²). The first planting date (20 June) gave the highest mean head area (389.05 cm²), whereas the third planting date (10 July) gave the lowest mean (328.07 cm²). The interaction treatments Argensun × first planting date and Selected Argensun × first planting date recorded the highest head area (430.00 cm²), while Zahra Al-Iraq × third planting date recorded the lowest value (280.00 cm²).