Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/11/2013
Publication Date: 5/14/2013
Citation: Molnar, T., Walsh, E., Capik, J., Sathuvalli, V., Mehlenbacher, S., Rossman, A.Y., Zhang, N. 2013. A real-time PCR assay for early detection of eastern filbert blight. Plant Disease. 97:813-818. Interpretive Summary: Fungi cause billions of dollars damage to agricultural crops each year. One fungus causes a disease of hazelnut that is called Eastern filbert blight. Because of this present of this fungus on native hazelnuts, hazelnuts cannot be grown in the eastern United States; most hazelnuts or filberts are grown in Oregon. Unfortunately, this fungus was introduced into the western United States in the mid-1960’s and has been causing problems in hazelnut orchards there. Although plant breeders are working to develop resistant varieties of hazelnut, this work is hindered by the long time it takes to detect the disease-causing fungus in new potentially resistant varieties. To solve this problem a test was developed that allows the fungus to be detected in plant material even when no sign of disease is visible. This test is rapid and accurate allowing plant breeders to detect the presence of the plant pathogen within fifteen weeks after inoculation. Using this test plant breeders will be able to screen quickly for the presence of the pathogen and thus develop varieties of hazelnut that are resistant to Eastern filbert blight.
Technical Abstract: Eastern filbert blight (EFB) is a devastating disease of European hazelnut, Corylus avellana, which causes economic losses in Oregon where 99% of the U.S. crop is produced. The causal fungus, Anisogramma anomala, is native to eastern North America, where it is found associated with the American hazelnut (C. americana). While C. americana is tolerant, EFB causes cankers, branch dieback, and death of C. avellana. Detection and identification of A. anomala is time consuming using conventional methods because the disease symptoms only show after 12–16 months of incubation, and the fungus cannot be cultured from infested host tissues without sporulating perithecia. In this study, a culture-independent TaqMan real-time PCR assay was developed for A. anomala that enables pathogen detection from field samples within a few hours. The assay was validated with A. anomala, closely related species, common environmental microorganisms, and 100+ C. avellana samples. The detection limit of the assay is 0.1 pg A. anomala genomic DNA, which enables EFB diagnosis 5–11 months before disease symptoms develop. Compared with traditional diagnostic methods, the real-time PCR assay is more sensitive and fast. It will facilitate hazelnut breeding and disease management by early and accurate diagnosis of EFB.