Thu, Aug 05, 2021:On Demand
Background/Question/Methods:
Arbuscular mycorrhizal fungi (AMF) are belowground plant root mutualists that aid in mineral, nutrient, and water uptake while herbivores are a ubiquitous antagonist. Both influence key plant functional traits such as total leaf area, stomatal conductance, flower number and size, and fruit production. In addition, AMF and herbivore interactions may affect floral volatile emissions, an important modality critical to pollinator attraction. To investigate how these above and belowground species interactions shape key plant functional traits, we conducted a manipulative field-based experiment with three strawberry (Fragaria x ananassa) cultivars, representing unique genotypes. We used a fully-crossed factorial design where plants were exposed to AMF, herbivory, and the combined factors to determine effects on host plants. For the mycorrhizae treatment, we inoculated plant roots with Rhizophagus irregularis spores. For the herbivory treatment, we used a combined caterpillar, leaf clipping, and jasmonic acid treatment resulting in a 25% reduction in foliar area. In this study, we asked: what are the main and interactive effects of mycorrhizal inoculation, herbivory, and genotype on 1) plant physiological, growth, and reproductive traits, 2) floral volatile composition and emission rates, and 3) pollinator attraction?
Results/Conclusions: Overall, we found that genotype influenced strawberry functional traits more strongly in comparison to treatment effects, although these factors often interacted. For plant reproductive traits, however, biotic interactions were more important explanatory factors. Genotype was the best predictor of variation in photosynthetic rates and stomatal conductance. Initially, herbivory reduced conductance, but after a four-week recovery period, conductance was higher in herbivore-damaged plants. Mycorrhizal inoculation increased total leaf area, but only in plants that did not experience herbivory. AMF increased and herbivory decreased flower and fruit number by ~20%. Further, herbivory reduced total fruit weight by ~20%. Overall, genotype was a key predictor of variation in floral volatiles. Further, herbivory influenced volatile composition immediately after the treatment, and this effect depended on genotype. In particular, herbivory increased total terpenoid emissions, especially for ocimene isomers. A month after herbivory, these effects were not apparent, although genotype interacted with both herbivory and mycorrhizal inoculation to affect total volatile emissions. Our study demonstrates benefits of mycorrhizal inoculation for strawberry production under both conditions of no herbivore and significant herbivore damage. Ongoing and future research aims to link floral traits and pollinator visitation in order to evaluate genotype by environment effects on plant-pollinator interactions and plant productivity.
Results/Conclusions: Overall, we found that genotype influenced strawberry functional traits more strongly in comparison to treatment effects, although these factors often interacted. For plant reproductive traits, however, biotic interactions were more important explanatory factors. Genotype was the best predictor of variation in photosynthetic rates and stomatal conductance. Initially, herbivory reduced conductance, but after a four-week recovery period, conductance was higher in herbivore-damaged plants. Mycorrhizal inoculation increased total leaf area, but only in plants that did not experience herbivory. AMF increased and herbivory decreased flower and fruit number by ~20%. Further, herbivory reduced total fruit weight by ~20%. Overall, genotype was a key predictor of variation in floral volatiles. Further, herbivory influenced volatile composition immediately after the treatment, and this effect depended on genotype. In particular, herbivory increased total terpenoid emissions, especially for ocimene isomers. A month after herbivory, these effects were not apparent, although genotype interacted with both herbivory and mycorrhizal inoculation to affect total volatile emissions. Our study demonstrates benefits of mycorrhizal inoculation for strawberry production under both conditions of no herbivore and significant herbivore damage. Ongoing and future research aims to link floral traits and pollinator visitation in order to evaluate genotype by environment effects on plant-pollinator interactions and plant productivity.