Susceptibility of some Corylus avellana L. cultivars to Xanthomonas arboricola pv. corylina

Authors: WEBBER, BRYAN - Oregon State University; WADA, SUGAE - Oregon State University; Stockwell, Virginia; WIMAN, NIK - Oregon State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2021
Publication Date: 12/17/2021
Citation: Webber, B.J., Wada, S., Stockwell, V.O., Wiman, N.G. 2021. Susceptibility of some Corylus avellana L. cultivars to Xanthomonas arboricola pv. corylina. Frontiers in Plant Science. 12. Article 800339. https://doi.org/10.3389/fpls.2021.800339.
DOI: https://doi.org/10.3389/fpls.2021.800339

Interpretive Summary: Oregon growers produce 99% of the hazelnut crop in the USA. In the 1980's, hazelnuts orchards in Oregon were threatened by the introduction of the fungal pathogen that causes the devastating disease called Eastern filbert blight. Release of new Eastern filbert blight-resistant cultivars has revitalized hazelnut orchards and production in Oregon. Over the past 5 years, acreage of hazelnut trees in Oregon has increased from 30,000 to 50,000. Although the young trees are resistant to the fungal disease Eastern filbert blight, they easily damaged by the bacterial plant pathogen Xanthomonas arboricola pv corylina. This pathogen causes a disease called bacterial blight of hazelnut. The symptoms of bacterial blight include dead buds, branch die-back, and death of young hazelnut trees. Effective methods to control this disease have not been developed. Our research focused on determining the dose of the pathogen and the type of hazelnut tissue inoculated with the bacterial blight pathogen to cause repeatable and biologically-relevant levels of disease. The methods evaluated in this project will be useful to develop and evaluate technologies to control bacterial blight of hazelnut and other bacterial diseases of perennial nuts and fruits with woody stems.

Technical Abstract: Bacterial blight of hazelnut (Corylus avellana L.) is caused by Xanthomonas arboricola pv. corylina (Xac). In the past, bacterial blight has been a key disease impacting the Oregon hazelnut industry where 99% of the United States hazelnut crop is grown. The disease is re-emerging in young orchards, as acreage of newly released hazelnut cultivars rapidly increases. This increase in hazelnut acreage is accompanied by renewed interest in developing control strategies for bacterial blight. Information on susceptibility of hazelnut cultivars to Xac is limited, partially due to lack of verified methods to quantify hazelnut cultivar response to artificial inoculation. In this research, Xac inoculation protocols were adapted to two hazelnut growing environments to evaluate cultivar susceptibility: in vitro tissue culture under sterile and controlled conditions, and in vivo potted tree conditions. Five hazelnut cultivars were evaluated using the in vitro inoculation protocol and seven hazelnut cultivars were evaluated using the in vivo inoculation protocol. Under in vitro conditions, there were severe bacterial blight symptoms on each cultivar consistent with those seen in the field, but no significant differences in the susceptibility of the newly released cultivars were observed compared to known Xac-susceptible cultivar (“Barcelona”). Under in vivo conditions, the proportion of necrotic buds were significantly higher in “Jefferson” and “Dorris” compared to all of the other tested cultivars, including “Barcelona.” The symptom progression seen in vivo mirrored the timing and symptom progression of bacterial blight reported from field observations. The in vitro conditions significantly reduced the amount of time required to measure the inoculation efficiency compared to the in vivo environment and allowed for greater replication. Further studies on the effects of Xac can use the results of these experiments to establish a dose–response model for bacterial blight, a wider range of germplasm can be tested under in vitro conditions, and management strategies that can be evaluated on large populations of new cultivars using the in vivo methods.