Do plant ploidy and pollinator tongue length interact to cause low seed yield in red clover?

Abstract

The loss of long‐tongued pollinator species and dominance of a few short‐tongued generalist species, related to agricultural intensification in recent decades, may have consequences for the quality, quantity, and stability of yields in insect‐pollinated crops. Interestingly, the changes in pollinator community coincide with an increase in poor and variable seed yield in red clover, an important crop for green manure and forage production. However, to date we lack a holistic understanding of the factors that drive seed yield in red clover crops. To remedy this, we related plant and pollinator traits to pollinator visitation, behavior, and pollination efficiency in four diploid and five tetraploid red clover cultivars during three years in a common garden setting. Tetraploid cultivars produced 52% fewer seeds and 41% lower seed weight per flower head compared with diploid cultivars. They also had fewer flower heads per plant, larger florets, and lower pollen viability than diploids. Pollinator species with shorter tongues visited diploid cultivars more frequently than tetraploid cultivars. Pollinator species with longer tongues deposited more pollen and showed higher pollination efficiency in terms of seeds produced after single visits. Our results suggest that while both diploid and tetraploid red clover cultivars benefit from the presence of longer‐tongued pollinator species, seed yield in tetraploid cultivars may be more sensitive to the loss of these bumble bee species in intensively cultivated agricultural landscapes.

Pollinators, pests and yield—Multiple trade‐offs from insecticide use in a mass‐flowering crop

“…High weevil density reduced the experimental yield of unsprayed clover (within treated sites) and, to a lesser extent, final yield in untreated relative to treated clover. This little difference in final yield may be because diploid cultivars, unique in our study to untreated, organically-managed sites, are more able to set seed than tetraploid cultivars (Boelt et al, 2015;Hederström et al, 2021;Jing et al, 2021;Vleugels et al, 2015) and thus able to compensate (to some extent) for pest damage. Fertile cultivars, also observed within oilseed rape (Lankinen et al, 2018), are important for farmers wishing to maximise their yields (Boelt et al, 2015;Knapp et al, 2016), and fertility should be considered as an additional trait alongside pest-resistance and pollinator-dependency/attraction within the IPPM framework (Egan et al, 2020;Lundin et al, 2021).…”

“…All sites ( n = 21) were spaced more than 6 km apart, except for two sites 2 km apart, to ensure independent pollinator populations (Vaissière et al, 2011). Within a triplet clover sites were matched (where possible) by clover ploidy (diploid or tetraploid) since ploidy can influence flower size, flower resources and seed production (Boelt et al, 2015; Hederström et al, 2021; Rundlöf et al, 2018). Eight clover cultivars were included in this study: three unique to treated sites, three unique to un‐treated sites, and two shared between treated and untreated sites (Appendix S1).…”

Impacto de la polinización entomófila en la producción de semilla de trébol rojo, Trifolium pratense L. (Fabaceae) en Bahía Blanca, Argentina

“…Medias del número y peso de semillas por planta de trébol rojo, Trifolium pratense, utilizando diferentes tratamientos de polinización. Teniendo en cuenta varios de los componentes de rendimiento medidos (como peso y número de semilla) se puede inferir que el rendimiento de las parcelas polinizadas por B. pauloensis fue significativamente mejor (p<0,05) que el de A. mellifera, lo que coincide con los resultados obtenidos previamente (Vanommeslaeghe et al, 2018;Hederström et al, 2021;Jing et al, 2021a,b). Abejas solitarias, abejas melíferas y abejorros se reconocen como potenciales polinizadores del trébol rojo (Arretz & Macfarlane, 1986;Rao & Stephen, 2009;Salvarrey et al, 2017), resultando las especies de abejorros del género Bombus las más importantes para esta función en la mayoría de los trabajos de investigación.…”

“…Todavía no existe en la generalidad de los productores una conciencia sobre el riesgo que conlleva la merma y escasez de polinizadores, ni se cuenta con información científica regional sobre las poblaciones de especies silvestres (Kremen, 2005;Hederström et al, 2021;Jing et al, 2021a,b). Reclamar el reconocimiento de la apicultura como servicio de polinización y preservar a otros polinizadores requiere un soporte técnico que demuestre su importancia económico-productiva y ambiental, además de fundamentar técnicas de manejo y políticas públicas.…”

Improving pollen and nectar supply by identifying the red clover (Trifolium pratense) cultivars that attract most pollinators

“…This suggests that there may be a tension between agronomic benefits, favouring tetraploids, versus helping bees, favouring diploids. However, low seed yield is a major limitation on commercial tetraploid use, which is typically 20%-50% lower than diploid cultivars (Vleugels et al, 2019), and is partially caused by lower inflorescence density (Boelt et al, 2015;Hederström et al, 2021;Vanommeslaeghe et al, 2018;Vleugels et al, 2015Vleugels et al, , 2016Vleugels et al, , 2019. To increase seed yield and reduce the price of tetraploid seeds, selection for increased inflorescence density has been suggested (Steiner et al, 1997;Vleugels et al, 2015Vleugels et al, , 2019.…”