Phytoplasma infection renders cranberries more susceptible to above- and belowground insect herbivores

Authors: RODRIGUEZ-SAONA, CESAR - Rutgers University; SALAZAR-MENDOZA, PAOLO - University Of São Paulo; HOLDCRAFT, ROBERT - Rutgers University; Polashock, James

Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2024
Publication Date: 9/16/2024
Citation: Rodriguez-Saona, C., Salazar-Mendoza, P., Holdcraft, R., Polashock, J.J. 2024. Phytoplasma infection renders cranberries more susceptible to above- and belowground insect herbivores. Insect Science. 2024(0):1–16. https://doi.org/10.1111/1744-7917.13444.
DOI: https://doi.org/10.1111/1744-7917.13444

Interpretive Summary: False Blossom is an important bacterium-incited disease of cranberry. "The infection is know to influence above ground plant-insect interactions". The impact of these infections on belowground insects remains largely unexplored. In this study, we investigated whether infection of cranberry by this disease affects the performance and feeding behavior of a foliar feeder, spongy moth, and a root feeder, oriental beetle. The results showed that, generally, larvae of spongy moth and oriental beetle exhibited larger size and more efficient consumption of plant tissues in infected plants compared to uninfected ones. Moreover, infection was associated with stunted growth, elevated nitrogen content, and lower levels of plant defense compounds in both shoots and roots of infected cranberry plants compared to uninfected ones. Our findings indicate that false blossom disease increases plant nutrient levels and decreases defensive compounds, which may explain the enhanced performance of both above- and belowground herbivores on infected plants. These results will benefit researchers in developing new strategies to manage false blossom disease in cranberry.

Technical Abstract: While phytoplasma infections in plants are known to influence their interactions with aboveground herbivores, the impact of these infections on belowground herbivores remains largely unexplored. In cranberry (Vaccinium macrocarpon), infection by the phytoplasma Candidatus Phytoplasma sp. subgroup 16SrIII-Y leads to false blossom disease, a serious threat to the cranberry industry. In this study, we investigated whether infection of cranberry by this phytoplasma affects the performance and feeding behavior of a foliar feeder (spongy moth, Lymantria dispar) and a root feeder (oriental beetle, Anomala orientalis). To achieve this, we measured the survival, growth, and consumption of larvae of both insect herbivores on phytoplasma-infected and uninfected cranberries, utilizing two cranberry genotypes–the wild selection 'Ben Lear' and the recently released 'Crimson Queen’. To assess the effects on plant morphological and chemical traits, we also examined the impact of phytoplasma infection on shoot and root growth, carbon and nitrogen content, and the levels of defensive compounds such as proanthocyanidins (PACs). The results showed that, generally, larvae of L. dispar and A. orientalis exhibited larger size and more efficient consumption of plant tissues in phytoplasma-infected plants compared to uninfected ones; however, the strength of these effects was influenced by the cranberry genotype. Moreover, phytoplasma infection was associated with stunted growth, elevated nitrogen content, and lower PAC levels in both shoots and roots of infected cranberry plants compared to uninfected ones. In summary, our findings indicate that the cranberry phytoplasma manipulates the chemical composition of shoots and roots by increasing nutrient levels and decreasing defensive compounds, which may explain the enhanced performance of both above- and belowground herbivores on infected plants. These insights provide a new perspective on the complex interactions among plants, phytoplasma infection, and the community of insect herbivores.