Effect of selenium accumulation on foraging behavior of pollinators and seed yield in Trifolium alexandrinum L

Selenium (Se) is an essential nutrient for both plants and animals and is usually provided as a supplement to livestock. Se bioaccumulation promotes plant growth by enhancing the accumulation of organic solutes and the activation of antioxidant system. In animals, the Se supplements reduce the chances of mastitis and white muscle disease, and improve the immunity, health, and reproduction, particularly in lactating dairy cows. Therefore, the enrichment or biofortification of fodder crops with Se may improve the nutritional quality of forages and thereby reduce malnutrition in cattle. However, Se hyper-accumulation in plants or plant parts can cause direct toxic effects on insects especially bees. Berseem is a highly cross-pollinated fodder crop that attracts a large number of pollinators. However, little or no reports are available regarding the effects of Se biofortification on the foraging behavior of pollinators in berseem. Therefore, the current study was planned to evaluate the effect of exogenous application of Se on the foraging behavior of native pollinators visiting the berseem crop. Five different doses of Se were applied to evaluate its effect on abundance, foraging behavior (visit duration and visitation rate), and single-visit efficacy of native pollinators that may affect berseem seed yield. Our results showed maximum abundance of pollinators in plants supplemented with low Se level, i.e., 5 g ha^-1 while the minimum abundance was observed at high Se doses (15 and 20 g ha^-1). Also, the seed yield attributes, i.e., the number of seeds per head, seed weight per head, 1000 seed weight, were the highest in plants treated with a low dose of Se, whereas the seed yield of berseem decreased with an increase in Se concentrations. Hence, our study provides evidence that high doses of Se negatively affect the foraging behavior of pollinators (visitation rate and visit duration) in plants. We conclude that the application of moderate Se dose positively influences the pollination ecology of berseem, consequently improving seed yield. HIGHLIGHTS: Selenium (Se) is essential for animals and beneficial for plants and may become toxic at high level. Se is delivered to the environment due to agriculture. Se toxicity affected berseem growth and considerably reduced the seed yield. High dose of Se reduced the abundance of pollinators and negatively affected their foraging behavior.