Bee Pollinators Enhance B-onion Seed Production in the Dry Zone of Sri Lanka

Production of B-onion (Allium cepa), a key cash crop in Sri Lanka, falls short of consumer demand due to limited quality seeds and high cost of commercial seeds. This study investigated the role of insect pollination on B-onion seed production in the dry zone, Sri Lanka, focusing on key pollinators, seed yield, weight and germinability. Experimental plots were established in a home garden in Sigiriya, selecting 50 umbels; 25 opened to insects and 25 covered. Diurnal insect visits and floral resources were observed. Seed yield and germinability were compared between opened and covered flowers. Halictus lucidipennis was the highest frequent visitor, followed by Apis cerana and A. florea. Nesting sites of H. lucidipennis were observed within the plots. Bee visitation was higher between 8:00-9:00 am, coinciding with pollen foraging, while nectar foraging remained throughout the day. The species-specific foraging patterns highlighted that H. lucidipennis and A. cerana were most active around 8:00-9:00 am for pollen foraging, whereas A. florea preferred midday (between 12:00-1:00 pm) for nectar foraging. Apis cerana preferred nectar foraging around 4:00-5:00 pm. Open umbels had significantly higher seed number and weight than covered umbels (P = 0.00). Germination percentage was also significantly higher in open-pollinated seeds than covered seeds using both petri dish and envelope methods (P = 0.02 and P = 4.007e-06), with longer seedlings after eight days (P = 0.00 and P = 4.499e-11). These findings highlight the importance of bees in enhancing B-onion seed production. Future research should assess next-generation plant vigor and compare pollinator efficiency.