From petals to seeds: Understanding the role of hymenopteran and dipteran pollinators in the reproductive success of onion (Allium cepa L.)

Abstract

An experiment was conducted to assess the pollinator community of onion (Allium cepa L.) as well to find the 
pollinators contributing to a higher onion seed production. Fifteen insect pollinator species belonging to two 
orders and two families were found to be visiting onion flowers. The dwarf honeybee, Apis florea F. 
(Hymenoptera: Apidae) was most frequent pollinator among bees. The maximum visitation rate was recorded 
in the case of Eristalinus aeneus S. (Diptera: Syrphidae), while the maximum stay time was recorded for A. 
florea. For observing the pollination effectiveness, we used pollinator exclusive approach, and four pollination 
trials were maintained i.e., 100%, 50%, 25% and 0% pollination. Pollinator effectiveness was accessed in terms 
of yield parameters such as umbel weight, number of seed and seed weight. Compared to 0% pollination, plants 
with 100% and 50% pollination levels showed 44- and 19-times higher seed production in onion, respectively. 
Six major pollinators were tested for their pollination efficiency. The single visit efficiency in terms of the 
number of seeds showed that plants with A. florea pollination showed higher seed yield. There was an increase 
in the number of seeds and seed weight per umbel, proving that A. florea is an effective pollinator in onion 
production. Moreover, syrphid flies also contributed to the onion seed production, though they were less 
efficient pollinators.