Linking bird resistant and susceptible sunflower traits with pollinator’s fauna and seed production

Sunflower (Helianthus annus L.) is a highly cross-pollinated crop dependent on insect pollinators to provide a good quality edible oil worldwide. Different sunflower hybrids vary in terms of dependence on insect pollinators. Previously few studies have been conducted regarding the role of insect pollinators in hybrid sunflower seed production in Pakistan. Therefore, the current study was planned to explore the abundance and diversity along with foraging behavior (visitation rate and stay time) of native insect pollinators as well as to study the effect of different pollination treatments (free insect visits vs. no insect visits) on the reproductive success of different hybrids of sunflower. Two sunflower hybrids were grown at the research farm of MNS University of Agriculture, Multan, under the Randomized Complete Block Design (RCBD). In our study, the pollinator community consisted of honeybees (Apis dorsata, A. mellifera, and A. florea), solitary bees (Pseudapis sp., Megachilidae sp. and Xylocopa sp.), and syrphid flies (Eristalinus aeneus and E. megacephalus). Furthermore, the relative abundance of pollinators was high in the H4 (having a flat head with 45º head angle from the stem) hybrid, while the least abundance was observed in H3 (180º head angle from stem). H4 proved to be a better hybrid among the hybrids regarding the number of seeds and seed weight. Both bees, i.e., solitary bees and honey bees, are crucial for pollinating sunflower. Comparative results of free insect visits and no insect visit treatments showed that the maximum number of seed weight, number of seeds, and seed diameter was observed in free insect visits compared to no insect visit treatment. Therefore, conserving the diversity of the native insect pollinators will lead to a higher yield of sunflower hybrids and other cross-pollinated crops.