Effects of genotype, growing conditions, and several parameters of sunflower attractiveness for bee visitation

Abstract

Effects of genotype and fertilizers on the production and availability of nectar and visitation by pollinators were analyzed. We analyzed four sunflower hybrids (Velja, NS-H-45, NS-H-111 and NS-H-702) and their parental lines grown in three fertilization treatments. Disc flower corolla length and nectar content were studied in the hybrids and their parental lines. The monitoring of bee visitation at flowering was done nine times per day. Nectar content was determined with the use of the micropipette method. The flower nectar content differed significantly among the genotypes, ranging from 2.53 mg/10 flowers (Velja) to 15.57 mg/10 flowers (Ha-98B) in 2002, and from 2.45 mg/10 flowers (Velja) to 9.65 mg/10 flowers (Ha-74A) in 2003. The highest average nectar content in 2002 (7.36 mg/10 flowers) was found in the control treatment and the lowest (6.67 mg/10 flowers) in the 100:100:100 NPK treatment, while in the next year we obtained the opposite results. The highest bee attendance was recorded in NS-H-111 in the first year and in NS-H-702 in the second year, and the lowest in Velja in both years. The largest bee attendance was recorded in the 50:50:50 treatment in both years. Corolla length in the treatments ranged from 9.11 mm (control) to 9.23 mm (100:100:100), while in the genotypes it ranged between 7.95 mm (Ha-26B) and 11.14 mm (CMS-3-8B). The longest corollas were found in flowers whose pistils had not yet emerged (9.51 mm). The largest bee attendance was observed at 0900h.