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Conrad_AO_2015_Dissertation final.pdf (3.76 MB)

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Metabolomics of Quercus spp. to understand and predict resistance to Phytophthora ramorum

Conrad, Anna O
http://rave.ohiolink.edu/etdc/view?acc_num=osu1429716653

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Plant Pathology.
Sudden oak death (SOD) is a devastating disease of oak and tanoak in the western United States, caused by the non-native, generalist pathogen Phytophthora ramorum Werres et al. Quercus agrifolia Nee (CLO—coast live oak) is a highly susceptible host of P. ramorum in California forests and Quercus rubra L. (NRO—northern red oak) is an important Eastern forest species that is also susceptible to P. ramorum. CLO naturally resistant to P. ramorum have been observed and include trees that fail to develop symptoms of infection or appear to recover after symptom development. Variability in CLO susceptibility has been associated with variation in the concentration of certain phenolic compounds produced in CLO phloem tissue, and putative phenolic biomarkers of resistance were identified from trees already infected with P. ramorum. However, the association between constitutive (i.e. pre-infection) levels of phenolics in naive CLO and variation in host susceptibility has not been examined, and little is known about the relationship between NRO susceptibility and variation in phenolic levels. This research aimed to elucidate chemical mechanisms of resistance and identify factors that may affect the production of phenolic defenses in susceptible Quercus spp., including CLO and NRO, before and after infection with P. ramorum. Time was a significant explanatory factor for the variability of certain phenolics, both within and between years, though overall variation was low and did not appear to be related to variability in CLO susceptibility to P. ramorum. NRO treated with a known, phosphonate-based elicitor of host defenses, were more resistant to P. ramorum, and both constitutive and induced levels of certain phenolics were also significantly impacted. Additionally, new approaches for identifying naturally resistant CLO based solely on constitutive concentrations of phenolics were tested. Four phenolic biomarkers of resistance were partially identified in CLO phloem collected before P. ramorum infection and were used to estimate the probability of CLO resistance and survival following infection with P. ramorum. Finally, this research demonstrated that Fourier-transform infrared (FT-IR) spectroscopy, combined with multivariate statistical analysis, can be used to distinguish between resistant and susceptible CLO prior to infection. The ability to identify resistant trees within forest stands could be a valuable tool for conserving and breeding resistant germplasm and identifying areas at risk of SOD. Moreover, the approaches utilized in these studies to identify resistant trees may be useful in other systems where forest pests and pathogens are of concern.
Pierluigi Bonello (Advisor)
Laurence Madden (Committee Member)
P. Larry Phelan (Committee Member)
Thomas Mitchell (Committee Member)
192 p.
Plant Pathology
Quercus; disease resistance; phenolics; sudden oak death; Phytophthora ramorum

Recommended Citations

Citations

  • Conrad, A. O. (2015). Metabolomics of Quercus spp. to understand and predict resistance to Phytophthora ramorum [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429716653

    APA Style (7th edition)

  • Conrad, Anna. Metabolomics of Quercus spp. to understand and predict resistance to Phytophthora ramorum . 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1429716653.

    MLA Style (8th edition)

  • Conrad, Anna. "Metabolomics of Quercus spp. to understand and predict resistance to Phytophthora ramorum ." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429716653

    Chicago Manual of Style (17th edition)

osu1429716653
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