Direct and Pollinator-Mediated Effects of Herbivory on Strawberry and the Potential for Improved Resistance

Abstract

The global decline in pollinators has partly been blamed on pesticides, leading some to propose pesticide-free farming as an option to improve pollination. However, herbivores are likely to be more prevalent in pesticide-free environments, requiring knowledge of their effects on pollinators, and alternative crop protection strategies to mitigate any potential pollination reduction. Strawberry leaf beetles (SLB) Galerucella spp. are important strawberry pests in Northern Europe and Russia. Given that SLB attack both leaf and flower tissue, we hypothesized pollinators would discriminate against SLB-damaged strawberry plants (Fragaria vesca, cultivar ‘Rügen’), leading to lower pollination success and yield. In addition we screened the most common commercial cultivar ‘Rügen’ and wild Swedish F. vesca genotypes for SLB resistance to assess the potential for inverse breeding to restore high SLB resistance in cultivated strawberry. Behavioral observations in a controlled experiment revealed that the local pollinator fauna avoided strawberry flowers with SLB-damaged petals. Low pollination, in turn, resulted in smaller more deformed fruits. Furthermore, SLB-damaged flowers produced smaller fruits even when they were hand pollinated, showing herbivore damage also had direct effects on yield, independent of indirect effects on pollination. We found variable resistance in wild woodland strawberry to SLB and more resistant plant genotypes than the cultivar ‘Rügen’ were identified. Efficient integrated pest management strategies should be employed to mitigate both direct and indirect effects of herbivory for cultivated strawberry, including high intrinsic plant resistance.

Capturing genetic variation in crop wild relatives: An evolutionary approach

“…concurs with findings on neutral genetic variation in several of our collected accessions (Hilmarsson et al., 2017). Coupled with previous findings on the value of wild‐derived traits in this CWR (Muola et al., 2017), we surmise that the evolutionarily relevant proxies established here for F. vesca could be of value to future germplasm collection or preservation initiatives throughout this subspecies' wide Eurasian range.…”

“…(b) Plotted values of SIMI for each genotype point. Points are mapped against a regional surface map of landscape isolation, in which warmer colours indicate habitat patches with greater relative isolation from other similar patches in the region −10,000 0 10,000 20,000 30,000 40,000 −2 0 2 4 6 Landscape isolation distance Plant size genetic distance (a) (b) 920 -7445 7446 -12,882 12,883 -19,182 19,183 -26,822 26,823 -57,136 Landscape Similarty Index in this CWR (Muola et al, 2017), we surmise that the evolutionarily relevant proxies established here for F. vesca could be of value to future germplasm collection or preservation initiatives throughout this subspecies' wide Eurasian range.…”

Plant resistance does not compromise parasitoid-based biocontrol of a strawberry pest

“…The 16 plant genotypes used in this study were derived from distinct wild populations in Uppsala County, Sweden, during spring 2012 24,25,49 (Supplementary Material Table 1). The entire collection consists of 86 plant genotypes that have been screened for resistance against the strawberry leaf beetle 25 .…”

Identification and field evaluation of (E)‐11,13‐tetradecadienal as sex pheromone of the strawberry tortrix (Acleris comariana)

“…In addition, infestation rates were higher in 3 years old fields vs. younger fields, indicating a build-up of populations over time. Direct estimates of the abundance of small and malformed berries in relation to A. comariana infestation is difficult to gather because several factors can cause such low-quality berries, for example poor pollination (Andersson, Rundlöf, & Smith, 2012;Muola et al, 2017), transfer of low-quality pollen (Ariza, Soria, Medina, & Martinez-Ferri, 2011) or infestation by other insects, for example other tortricid moths or thrips.…”