Cranberry Resistance to Dodder Parasitism: Induced Chemical Defenses and Behavior of a Parasitic Plant

Abstract

Parasitic plants are common in many ecosystems, where they can structure community interactions and cause major economic damage. For example, parasitic dodder (Cuscuta spp.) can cause up to 80-100 % yield loss in heavily infested cranberry (Vaccinium macrocarpon) patches. Despite their ecological and economic importance, remarkably little is known about how parasitic plants affect, or are affected by, host chemistry. To examine chemically-mediated interactions between dodder and its cranberry host, we conducted a greenhouse experiment asking whether: (1) dodder performance varies with cranberry cultivar; (2) cultivars differ in levels of phytohormones, volatiles, or phenolics, and whether such variation correlates with dodder parasitism; (3) dodder parasitism induced changes in phytohormones, volatiles, or phenolics, and whether the level of inducible response varied among cultivars. We used five cranberry cultivars to assess host attractiveness to dodder and dodder performance. Dodder performance did not differ across cultivars, but there were marginally significant differences in host attractiveness to dodder, with fewer dodder attaching to Early Black than to any other cultivar. Dodder parasitism induced higher levels of salicylic acid (SA) across cultivars. Cultivars differed in overall levels of flavonols and volatile profiles, but not phenolic acids or proanthocyanidins, and dodder attachment induced changes in several flavonols and volatiles. While cultivars differed slightly in resistance to dodder attachment, we did not find evidence of chemical defenses that mediate these interactions. However, induction of several defenses indicates that parasitism alters traits that could influence subsequent interactions with other species, thus shaping community dynamics.

Phenolic Compound Induction in Plant-Microbe and Plant-Insect Interactions: A Meta-Analysis

“…Among final considerations, this effort to analyze a host biochemical response to infection or infestation revealed some gaps in literature and considerations need to be made in future research. Studies examining host physiological responses to many major pathogen groups are sorely lacking, by directly assessing phytocompound levels and not only transcripts of pathway genes, in particular those observing how host plants react to infections by nematodes (Kaplan et al, 2008a,b;Singh et al, 2012;Alves et al, 2016), oomycetes (Sahoo et al, 2009;Korgan et al, 2011), parasitic plants (Runyon et al, 2008;Tjiurutue et al, 2016), and viruses/viroids (Harish et al, 2009;Baker et al, 2010;Wallis and Sudarshana, 2016). The ability to fully assess whether these compounds have consistent responses is considered to remain unknown.…”

Infestation of Field Dodder (Cuscuta campestris Yunck.) Promotes Changes in Host Dry Weight and Essential Oil Production in Two Aromatic Plants, Peppermint and Chamomile

“…Considering the very low δ-cadinene level (0.09%), it seems that peppermint plants do not metabolize any additional components in response to the presence of field dodder. In addition, the essential oil of infested peppermint plants ( Table 3 ) did not contain compounds previously reported for different Cuscuta species (vanillin, eugenol, α-cadinene) [ 35 , 36 ], or nonanal as a compound involved in chemical defense and one responsible for host colonization by Cuscuta species [ 37 ].…”

Parasite Removal, but Not Herbivory, Deters Future Parasite Attachment on Tomato

“…Potential differences in phytohormonal responses to parasitic plants and herbivores may provide an additional explanation for why herbivory did not affect subsequent parasitism. Dodder parasitism marginally induced SA production in cranberry hosts [ 52 ], and both SA and JA signaling pathways in tomato [ 48 ]. Generally, chewing insects such as caterpillars activate the JA-signaling pathways [ 6 ].…”