Impact of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Infestation on the Jasmonic Acid-Elicited Defenses of Tsuga canadensis (Pinales: Pinaceae)

Hemlock woolly adelgid is an invasive piercing-sucking insect in eastern North America, which upon infestation of its main host, eastern hemlock (‘hemlock’), improves attraction and performance of folivorous insects on hemlock. This increased performance may be mediated by hemlock woolly adelgid feeding causing antagonism between the the jasmonic acid and other hormone pathways. In a common garden experiments using hemlock woolly adelgid infestation and induction with methyl jasmonate (MeJA) and measures of secondary metabolite contents and defense-associated enzyme activities, we explored the impact of hemlock woolly adelgid feeding on the local and systemic induction of jasmonic acid (JA)-elicited defenses. We found that in local tissue hemlock woolly adelgid or MeJA exposure resulted in unique induced phenotypes, whereas the combined treatment resulted in an induced phenotype that was a mixture of the two individual treatments. We also found that if the plant was infested with hemlock woolly adelgid, the systemic response of the plant was dominated by hemlock woolly adelgid, regardless of whether MeJA was applied. Interestingly, in the absence of hemlock woolly adelgid, hemlock plants had a very weak systemic response to MeJA. We conclude that hemlock woolly adelgid infestation prevents systemic induction of JA-elicited defenses. Taken together, compromised local JA-elicited defenses combined with weak systemic induction could be major contributors to increased folivore performance on hemlock woolly adelgid-infested hemlock

Seasonal changes in eastern hemlock (\u3cem\u3eTsuga canadensis\u3c/em\u3e) foliar chemistry

Eastern hemlock (Tsuga canadensis (L.) Carriére; hemlock) is an eastern North American conifer threatened by the invasive hemlock woolly adelgid (Adelges tsugae Annand). Changes in foliar terpenes and phenolics were evaluated in new (current year growth) and mature (1-year old growth) hemlock needles during the growing season and into plant dormancy. From April through September, foliar concentrations of non-volatile soluble phenolics, condensed tannins, lignin, mono- and sesquiterpenes α-pinene, camphene, isobornyl acetate, and diterpene resin were quantified. After September, additional analyses of metabolites that continued to differ significantly in new versus mature foliage were carried out. Total soluble phenolic concentration and condensed tannin concentration in new foliage remained low relative to mature foliage throughout the growing season and converged in December. Lignin concentration in new foliage converged with that of mature foliage by July. Concentrations of α-pinene, camphene, isobornyl acetate, and diterpene resin in new foliage converged with mature foliage within one month of budbreak. The convergence of terpene concentrations in new and mature foliage suggests that these metabolites may play a role in herbivore defense during the peak growing season. Conversely, soluble phenolics, including condensed tannins, may defend foliage from herbivory outside of the spring growth period

Jazz Guitar Ensemble and Jazz Combos

Kennesaw State University School of Music presents Jazz Guitar Ensemble and Jazz Combos.https://digitalcommons.kennesaw.edu/musicprograms/1422/thumbnail.jp

It’s not easy being green: A study of the chemical phenology of the Eastern Hemlock throughout a growing season

Phenology is the study of seasonally timed developmental events that are driven by environmental cues. Phenolic compounds and terpenoids are the two main classes of secondary metabolites present in conifer needles, and speaking generally, they correlate with needle age. Understanding the phenology of secondary metabolites is important, since variation in these compounds can affect a tree’s resistance to pest and pathogen attack. Terpenoids function in a wide array of ecological processes vital to conifer survival, including regulating forest dynamics through allelopathic inhibition of seed germination, altering rates of soil nutrient cycling and nitrification, and conferring resistance to pathogenic fungi and insect herbivory. Phenolics are equally diverse, contributing to needle structural development, toughness and defense against insect herbivore attack. We present the results of a study evaluating changes in foliar terpenoid and phenolic compounds over the course of a growing season, from April through September with additional time points in December and January, to provide a complete first picture of Eastern Hemlock chemical phenology. The present study aimed to (i) describe temporal patterns of non-volatile alpha-pinene, camphene, diterpene acid and isobornyl acetate concentrations in both expanding needles and mature needles from the previous year’s growth, (ii) to describe temporal patterns of tannin, lignin and total phenolic compound levels in the same foliage classes, and (iii) to identify at what point in the growing season the levels of these metabolites in expanding needles converge on levels present in mature needles. We hypothesized that the relative abundances of structural and defensive metabolites will show an inverse relationship in expanding needles, mature needles will exhibit elevated levels of defensive metabolites during growth, but with less variability than new foliage, and that the levels of all metabolites in new foliage will reach those of mature foliage by the end of the growing season

Impact of chronic stylet-feeder infestation on folivore-induced signaling and defenses in a conifer

Our understanding of how conifers respond biochemically to multiple simultaneous herbivore attacks is lacking. Eastern hemlock (Tsuga canadensis; \u27hemlock\u27) is fed on by hemlock woolly adelgid (Adelges tsugae; \u27adelgid\u27) and by later-instar gypsy moth (Lymantria dispar; \u27gypsy moth\u27) caterpillars. The adelgid is a stylet-feeding insect that causes a salicylic acid (SA)-linked response in hemlock, and gypsy moth larvae are folivores that presumably cause a jasmonic acid (JA)-linked response. This system presents an opportunity to study how invasive herbivore-herbivore interactions mediated through host biochemical responses. We used a factorial field experiment to challenge chronically adelgid-infested hemlocks with gypsy moth caterpillars. We quantified 17 phytohormones, 26 phenolic and terpene metabolites, and proanthocyanidin, cell wall-bound (CW-bound) phenolic, and lignin contents. Foliage infested with adelgid only accumulated gibberellins and SA; foliage challenged by gypsy moth only accumulated JA phytohormones. Gypsy moth folivory on adelgid-infested foliage reduced the accumulation of JA phytohormones and increased the SA levels. Both herbivores increased CW-bound phenolics and gypsy moth increased lignin content when feeding alone but not when feeding on adelgid-infested foliage. Our study illustrates the importance of understanding the biochemical mechanisms and signaling antagonism underlying tree responses to multiple stresses and of disentangling local and systemic stress signaling in trees