Identification of Quercus agrifolia (coast live oak) resistant to the invasive pathogen Phytophthora ramorum in native stands using Fourier-transform infrared (FT-IR) spectroscopy

Abstract

Over the last two decades coast live oak (CLO) dominance in many California coastal ecosystems has been threatened by the alien invasive pathogen Phytophthora ramorum, the causal agent of sudden oak death. In spite of high infection and mortality rates in some areas, the presence of apparently resistant trees has been observed, including trees that become infected but recover over time. However, identifying resistant trees based on recovery alone can take many years. The objective of this study was to determine if Fourier-transform infrared (FT-IR) spectroscopy, a chemical fingerprinting technique, can be used to identify CLO resistant to P. ramorum prior to infection. Soft independent modeling of class analogy identified spectral regions that differed between resistant and susceptible trees. Regions most useful for discrimination were associated with carbonyl group vibrations. Additionally, concentrations of two putative phenolic biomarkers of resistance were predicted using partial least squares regression; >99% of the variation was explained by this analysis. This study demonstrates that chemical fingerprinting can be used to identify resistance in a natural population of forest trees prior to infection with a pathogen. FT-IR spectroscopy may be a useful approach for managing forests impacted by sudden oak death, as well as in other situations where emerging or existing forest pests and diseases are of concern.

Induced antimicrobial activity in heat‐treated woodchips inhibits the activity of the invasive plant pathogen Phytophthora ramorum

“…Phenolics, such as ellagic acid and a tyrosol derivative, have already been found in the phloem of Quercus agrifolia (coast live oak), another species frequently infected by P. ramorum in the mixed-evergreen forests of California. Surviving coast live oaks appear to have constitutively higher levels of these phenolics than more P. ramorum-susceptible individuals, suggesting the compounds would be good candidates for examination as potential biomarkers for resistance to P. ramorum (Nagle et al, 2011;Conrad et al, 2014). For the same reasons, a greater understanding of what compounds are induced in Japanese larch bark during the early stages of pathogen attack could provide insights into what resistance mechanisms against P. ramorum are already operating.…”

“…Swain et al, 2006) and searching for resistance (e.g. Conrad et al, 2014). Many of these disease-focused studies have been summarized by Kliejunas (2010), but he also concluded that no single strategy is likely to be effective in eradicating P. ramorum, especially once it has established in the wider environment.…”

Temporal metabolic profiling of the Quercus suber–Phytophthora cinnamomi system by middle‐infrared spectroscopy

“…Hence, the rapid screening capacity and ability to detect unforeseen metabolic alterations in biological systems makes FT-IR spectroscopy a suitable technique to be used prior to any targeted metabolite analysis (Chalmers and Griffiths 2002). Nevertheless, the use of FT-IR spectroscopy in woody plant-pathogen interactions is scarce and even more singular when the considering temporal effects (Mart ın et al 2005;Allwood et al 2006;Cameron et al 2006;Martin et al 2007Martin et al , 2008Conrad et al 2014;Vivas et al 2014). So, to our knowledge, this article is the first to describe temporal changes in the metabolic patterns of early interaction between cork oak roots and P. cinnamomi by FT-IR spectroscopy.…”

“…; Conrad et al. ). However, because biological systems are composed of a myriad of polymers, macromolecules and metabolites, their infrared spectra are obviously highly complex, comprising the relative contributions from different functional groups, chemical structures and their interactions (Kamnev et al.…”

“…Among different metabolic approaches, metabolic profiling has appeared as a useful analytical tool to investigate plant-pathogen interactions (Fiehn 2002;Cameron et al 2006). One of the metabolic profiling techniques, the Fourier transform-infrared (FT-IR) spectroscopy, has been applied successfully for differentiation of functional biochemical groups in plants challenged by abiotic perturbations and/or biotic interactions (Gidman et al 2003;Mart ın et al 2005;Martin et al 2008;Conrad et al 2014). However, because biological systems are composed of a myriad of polymers, macromolecules and metabolites, their infrared spectra are obviously highly complex, comprising the relative contributions from different functional groups, chemical structures and their interactions (Kamnev et al 1997).…”