Epsilon Archive for Student Projects

Abstract

Red clover (Trifolium pratense) is an important crop grown in many temperate parts of the world.
To improve vegetative strength and green mass yield, breeding of tetraploid red clover cultivars is
common. Tetraploid cultivars are characterized by larger plants and flowers and improved resistance
against biotic and abiotic stress. Seed yield from tetraploid cultivars however is variable and
suboptimal from diploid cultivars. Red clover reproduction is dependent on insect mediated
pollination. Decline and shifts in communities among pollinator species are thought of as one factor
affecting seed yield in red clover. Other possible factors affecting seed yield are cultivation method
or genetic differences in tetraploid cultivars. We studied pollinator abundance and species presence
in four cultivars of different ploidy across regions in Sweden, from north to south, and compared
with seed yield. We also looked at different pollinator groups, as Nymphalidae and Autographa
gamma that are commonly found in red clover fields to see if they contribute to pollination. Changes
in ploidy could lead to floral trait loss and we investigated abundance and changes in flower specific
volatiles emitted from four cultivars and changes in volatiles emitted postpollination. Results from
this study are that there is no preference among pollinators between red clover cultivars, but
inflorescence density is of great importance for pollinator abundance. Our results show consistent
differences in seed yield across regions and sites indicating that there are genetic differences in seed
yield between cultivars. Pollinator abundance also had an effect on seed yield when comparing
across Sweden. Moreover, Nymphalidae does not contribute to pollination in red clover but
Autographa gamma does to a certain extent. Flower specific volatiles varies in abundance between
cultivars and a that there appears to be a postpollination effect on volatiles emitted. In conclusion
this study strengthens the importance of pollinators for seed production in red clover but also shows
that other factors as genetical differences need to be further investigated.

Keywords: Red clover, Trifolium pratense, seed yield, seed production, ploidy, pollinator,
pollination