Benefits of Insect Pollination to Confection Sunflowers Differ Across Plant Genotypes

Abstract

Sunflower (Helianthus annuus L.) is a major global crop that shows variable dependence on insect pollinators across systems (e.g., hybrid seed production, oilseed, and confection systems), growing regions, and plant genotypes. Although modern sunflowers have been bred for increased self‐fertility, selfing rates still vary across genotypes, resulting in differing pollinator dependence. Furthermore, some plant genotypes may attract a greater abundance or diversity of pollinators, thereby receiving greater pollinator benefits. The goal of this study was to evaluate the benefits of insect pollination to different modern confection sunflower varieties. We conducted pollinator exclusion experiments for 15 confection hybrid varieties in 2014 and 2015 to measure self‐fertility and pollinator‐mediated yield increases. To assess whether pollinator benefits differ across hybrids due to their relative attractiveness to pollinators, we compared bee visitation rates among hybrids and related these rates to seed mass. Overall, sunflower seed mass was 26% higher on open flowers than on bagged ones. Furthermore, seed mass on open flowers increased significantly with pollinator visitation rates. Yield increases with insect pollination differed among hybrids, however, with 5 of 15 showing significant increases ranging from 39 to 108%. Pollinator visitation rates and degrees of self‐fertility also differed across these hybrids, in part explaining the variability in pollinator benefits that they received. Our study shows that insect pollinators increase confection sunflower yields, but benefits vary across hybrids due to their self‐fertility and relative attractiveness to pollinators.

Local and landscape factors affect sunflower pollination in a Mediterranean agroecosystem

“…In accordance with previous findings (carried out both in the same and in other areas) [ 30 , 44 , 45 , 67 , 68 ] our data confirm that in the study area honey bee is the most abundant pollinator of sunflower. Although in other contexts high numbers of other insects visiting sunflower have been observed [ 28 , 36 , 37 ], the disproportionate prevalence of honey bees recorded in this study can be explained by the historical [ 42 , 43 ] and ongoing nomadism conducted by local bee-keepers to produce sunflower honey, which is a common practice in Central Italy. On the other hand, the very low visitation rates by wild bees, hoverflies and butterflies might have been caused by: (i) the observation plot method, which commonly underestimates bee species richness in agricultural habitats [ 69 ], but, in the case of the present work, may also have introduced a possible bias in bee abundance; (ii) a truly scarce presence of these groups in the study area; or (iii) a shifting due to competition with honey bees.…”

“…On the contrary, the role of wild bees in sustaining sunflower pollination is less clear, since it appears more context dependent as a result of the wide diversity of wild bee species with, very often, important behavioural differences. In the native area of sunflower, North America, many different wild bees visit commercial sunflower [ 28 , 36 , 37 ], while wild Helianthus species are visited by up to 400 native wild bee species, including many oligolectic bees [ 38 , 39 ]. In addition, wild pollinators may indirectly increase sunflower pollination by affecting honey bee behaviour during sunflower visits [ 36 , 40 ], even if this hypothesis is not supported by data in other regions [ 41 ].…”

Using Nectar-Related Traits to Enhance Crop-Pollinator Interactions

“…Over 2 years in North Dakota, 15 commercial hybrids were grown with or without pollinators excluded (via fine mesh bags). Though some hybrids received no benefit from pollinators, open-pollination by insects increased yields by 26% when averaged across all hybrids, and five of the hybrids showed increases of 39–108% ( Mallinger and Prasifka, 2017b ). In part, variation in benefits from pollinators was explained by how attractive each hybrid was to bees, though nectar-related traits were not directly assessed for these hybrids.…”

Pollination biology of Albizia lebbeck (L.) Benth. (Fabaceae: Mimosoideae) with reference to insect floral visitors

“…Insects play a pivotal role in pollination of flowering plants (Kluser et al, 2010, Mallinger and Prasifka, 2017, Vanbergen and Initiative, 2013). According to Klein et al (2007), >75% of the wild plant species and agriculture crops depends upon insect pollination.…”