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Biochemical Mechanisms of Resistance and Susceptibility in the Pinus nigra - Diplodia sapinea Pathosystem

Sherwood, Patrick William

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Environment and Natural Resources.
To counter the constant barrage of biotic threats that limit their survival, plants have evolved complex perception and signaling networks that allow for the detection of attackers and the induction of appropriate defensive responses. One important aspect of defense is the production of antimicrobial metabolites, which make the plant less habitable to invading pathogens. These metabolites can be present constitutively, or produced after a threat has been detected, including systemically in a phenomenon known as systemic induced resistance (SIR), whereby tissues distal to an initial infection possess greater inherent resistance to subsequent attacks. This phenomenon is well established in herbaceous model plants, but its occurrence in trees and other non-traditional model plants are comparatively less understood, so new model systems are needed to understand how the SIR state is reached in trees. Therefore, a major focus of this research was to investigate the basis of SIR in the Austrian pine (Pinus nigra Arnold) – Diplodia sapinea (Fr.) Fuckel pathosystem, for which SIR has been previously demonstrated and linked to the accumulation of phenolic metabolites in the systemic tissues. The central objective of this research was to evaluate the role of phenolics in SIR, by examining their antifungal properties, characterizing the temporal spatial patterns of their induction, and determining the influence of resource availability on their function in resistance. A corollary objective was to study the effects of water stress on resistance properties. It was discovered that while phenolic compounds previously implicated in SIR possess potent antifungal properties in vitro, their induction in planta is highly variable, and often not associated with the SIR phenotype. Furthermore, constitutive phenolic metabolism is only moderately responsive to nutrient availability, while induced phenolics are even less affected by differences in resource levels. Investigations into the signaling mechanisms revealed that induction of SIR is independent of phloem connectivity between the site of induction and challenge, suggesting that other transmission avenues are available to trees. Lastly, drought stress was shown to significantly weaken plant resistance levels through a combination of stress induced changes in host physiology that predispose the plants to infection, and pathogen exploitation of these changes. Together this research has improved our understanding of the role of phenolic defenses in pines and furthered the development of the Austrian pine – Diplodia sapinea pathosystem, so that new avenues of plant-microbe interactions can be investigated.
Pierluigi Bonello, Dr. (Advisor)
303 p.

Recommended Citations

Citations

  • Sherwood, P. W. (2014). Biochemical Mechanisms of Resistance and Susceptibility in the Pinus nigra - Diplodia sapinea Pathosystem [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408640310

    APA Style (7th edition)

  • Sherwood, Patrick. Biochemical Mechanisms of Resistance and Susceptibility in the Pinus nigra - Diplodia sapinea Pathosystem. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1408640310.

    MLA Style (8th edition)

  • Sherwood, Patrick. "Biochemical Mechanisms of Resistance and Susceptibility in the Pinus nigra - Diplodia sapinea Pathosystem." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408640310

    Chicago Manual of Style (17th edition)