Plants, including grapevines, rely on a variety of physiological responses to combat infections and herbivory, including the increased production of phenolic and terpenoid compounds. Our understanding of the roles of these compounds in defense has increased greatly over the past decade. However, most studies are limited to one pest or pathogen on one host at a time, even though plants are known to encounter multiple threats at once. Therefore, research was undertaken to examine how plant species, especially grapevine, respond to microbial pathogen infection by bacteria, fungi, and viruses, and animal herbivory by nematodes and sharpshooters. Upon infection with the bacterial pathogen Xylella fastidiosa, the fungal pathogen Neofusicoccum parvum and Grapevine red blotch virus grapevines were observed to have increased phenolic levels early in the infection process, but terpenoid levels remained relatively similar to levels in non-infected plants. The root knot nematode was not observed to affect phenolics when colonizing grapevine, and terpenoids have yet to be examined. Glassy-winged sharpshooter activity did not alter grapevine phenolic compound levels but did increase levels of specific terpenoids (alpha-farnesene and beta-ocimene) presumably to attract parasitic wasps, a natural predator. Additional experiments are underway to observe how induced shifts in phenolic and terpenoid levels from one infection or infestation could affect another. Furthermore, a series of in vitro studies are underway to observe how phenolic compounds affect pathogen growth. These studies observed that increased phenolic levels were often ineffective at preventing pathogen growth, and, at times, could be utilized by certain pathogens to improve the survival of the microbe. Overall, the role of phenolic compounds in plant defense has proven to be complicated and varies depending on the host, pathogen, and environment of the pathosystem.

Exploring the role of phenolic and terpenoid compounds in grapevine defense against pathogens and insects

2019 Fall National Meeting

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