| Title: | Analysis of Volatile Profiles for Tracking Asymptomatic Infections of Phytophthora ramorum and Other Pathogens in Rhododendron |
| Author(s): | Thompson CH; McCartney MM; Roubtsova TV; Kasuga T; Ebeler SE; Davis CE; Bostock RM; |
| Address: | "Department of Mechanical and Aerospace Engineering, University of California, Davis, CA 95616. Department of Plant Pathology, University of California, Davis, CA 95616. Crops Pathology & Genetics Research Unit, United States Department of Agriculture-Agricultural Research Service, Davis, CA 95616. Department of Viticulture and Enology, University of California, Davis, CA 95616" |
| DOI: | 10.1094/PHYTO-10-20-0472-R |
| ISSN/ISBN: | 0031-949X (Print) 1943-7684 (Electronic) 0031-949X (Linking) |
| Abstract: | "Phytophthora ramorum is an invasive, broad host range pathogen that causes ramorum blight and sudden oak death in forest landscapes of western North America. In commercial nurseries, asymptomatic infections of nursery stock by P. ramorum and other Phytophthora species create unacceptable risk and complicate inspection and certification programs designed to prevent introduction and spread of these pathogens. In this study, we continue development of a volatile organic compound (VOC)-based test for detecting asymptomatic infections of P. ramorum in Rhododendron sp. We confirmed detection of P. ramorum from volatiles collected from asymptomatic root-inoculated Rhododendron plants in a nursery setting, finding that the VOC profile of infected plants is detectably different from that of healthy plants, when measured from both ambient VOC emissions and VOCs extracted from leaf material. Predicting infection status was successful from ambient volatiles, which had a mean area under the curve (AUC) value of 0.71 +/- 0.17, derived from corresponding receiver operating characteristic curves from an extreme gradient boosting discriminant analysis. This finding compares with that of extracted leaf volatiles, which resulted in a lower AUC value of 0.51 +/- 0.21. In a growth chamber, we contrasted volatile profiles of asymptomatic Rhododendron plants having roots infected with one of three pathogens: P. ramorum, P. cactorum, and Rhizoctonia solani. Each pathogen induced unique and measurable changes, but generally the infections reduced volatile emissions until 17 weeks after inoculation, when emissions trended upward relative to those of mock-inoculated controls. Forty-five compounds had significant differences compared with mock-inoculated controls in at least one host-pathogen combination" |
| Keywords: | Asymptomatic Infections North America *Phytophthora Plant Diseases *Rhododendron mass spectrometry metabolomics nursery detection oomycetes pathogen detection ramorum blight volatile organic compounds (VOCs); |
| Notes: | "MedlineThompson, Cai H McCartney, Mitchell M Roubtsova, Tatiana V Kasuga, Takao Ebeler, Susan E Davis, Cristina E Bostock, Richard M eng U01 EB022003/EB/NIBIB NIH HHS/ I01 BX004965/BX/BLRD VA/ U18 TR003795/TR/NCATS NIH HHS/ UG3 OD023365/OD/NIH HHS/ UL1 TR000002/TR/NCATS NIH HHS/ UL1 TR001860/TR/NCATS NIH HHS/ P30 ES023513/ES/NIEHS NIH HHS/ 2021/02/23 Phytopathology. 2021 Oct; 111(10):1818-1827. doi: 10.1094/PHYTO-10-20-0472-R. Epub 2021 Oct 23" |
