Genetic variation in herbivore resistance within a strawberry crop wild relative (Fragaria vesca L.)

Abstract

To decrease the dependency on chemical pesticides, the resistance of cultivated strawberry to pests needs to be increased. While genetic resources within domesticated varieties are limited, wild genotypes are predicted to show high heritable variation in useful resistance traits. We collected 86 wild accessions of Fragaria vesca L. from central Sweden and screened this germplasm for antibiosis (pest survival and performance) and antixenosis (pest preference) traits active against the strawberry leaf beetle (Galerucella tenella L.). First, extensive common garden experiments were used to study antibiosis traits in the sampled plant genotypes. Heritable genetic variation among plant genotypes was found for several antibiosis traits. Second, controlled cafeteria experiments were used to test for plant genetic variation in antixenosis traits. The leaf beetles avoided egg laying on plant genotypes possessing high antibiosis. This indicates a high degree of concordance between antibiosis and antixenosis and that the beetles' egg-laying behavior optimizes the fitness of their offspring. The existence of high genetic variation in key resistance traits suggests that wild woodland strawberry contains untapped resources that are sought to reduce pesticide dependence in cultivated strawberry. Given that only a very small portion of the species' distribution area was sampled, even higher variation may be expected at the continental scale. As a whole, the genetic resources identified in this study serve to strengthen the position of woodland strawberry as a key crop wild relative.

Wild strawberry shows genetic variation in tolerance but not resistance to a generalist herbivore

“…Many plant species show genetic variation in their resistance responses to herbivores (e.g., Bossdorf et al, 2005;Muola et al, 2010;Weber et al, 2020). In particular, Weber et al (2020) found high variation among the plant genotypes used in this study in resistance to a more specialized and coevolved herbivore (Galerucella tenella L.). The generally high mortality of S. littoralis feeding on all the plant genotypes observed in this study may reflect this herbivore's polyphagy, and lack of evolutionary history with woodland strawberry.…”

“…Plant resistance has received more attention than plant tolerance in studies of plant defenses against insect herbivores (Karban, 2011). Many plant species show genetic variation in their resistance responses to herbivores (e.g., Bossdorf et al., 2005; Muola et al., 2010; Weber et al., 2020). In particular, Weber et al.…”

“…To assess genetic variation in woodland strawberry's resistance to, and tolerance of, feeding damage by the generalist herbivore S. littoralis , and possible modulation of its responses by prior application of JA, we subjected 16 genotypes of the species (described by Weber et al., 2020) to four treatments (see below). The genotypes were selected from our archive of clones collected from various sites in Uppland, Sweden, in 2012 (Weber et al., 2020). Plant material for the experiment was propagated from runners collected from the clone archive that were maintained in a greenhouse providing 16‐hr light: 8‐hr dark, 20:16°C cycles.…”

Host suitability of three Opuntia taxa for the Dactylopius opuntiae (Hemiptera: Dactylopiidae) ‘stricta’ lineage

“…The beetles avoid laying eggs on certain host genotypes and this preference is linked to the insect's fitness. Closer to home, the metabolomic profiles of invasive populations of alien weeds in the Kruger National Park, South Africa, were shown to differ significantly from their native populations in the country of origin (Weber et al, 2019). These findings reveal that the organisms on both sides of the biological control relationship are constantly evolving, even in the notoriously stable associations that have been incorporated into biological control programmes (Müller-Schärer et al, 2020).…”

“…Alternatively, secondary metabolites similarity among potential host plants may explain host suitability of a specialised insect herbivore, sometimes more so than the phylogenetic relatedness of these particular plant species (Kergoat et al, 2005;Murphy & Feeny, 2006;Rapo et al, 2019). Weber et al (2019) have shown a population of wild strawberries to differ in their acceptability ('antixenosis' = beetle preference = acceptability) and suitability ('antibiosis' = beetle survival and performance = suitability) of the strawberry leaf beetle (Garelucella tennela L.). The beetles avoid laying eggs on certain host genotypes and this preference is linked to the insect's fitness.…”