2019 ASHS Annual Conference

Bacterial blight (Xanthomonas arboricola pv. corylina (Xac)) of hazelnut (Corylus avellana L.) was described first in Oregon in 1915 and is now recognized as a damaging disease of young hazelnut trees worldwide. Thousands of acres of new hazelnut cultivars are being planted in the Willamette Valley of Oregon where 99 percent of the US hazelnut crop is grown. There has been an increased incidence of bacterial blight in young hazelnut plantings and no quantitative research on bacterial blight susceptibility in the different hazelnut cultivars. Increased nursery production of hazelnut trees to meet the rising demand has been made possible through the development of the 2016 Corylus tissue culture medium optimized for hazelnut growth. In this study, tissue culture was used as a controlled environment to investigate the potential for developing a rapid screening technique to determine cultivar relative susceptibility to bacterial blight infection. Culture medium, stress conditions, and disease symptom progression were evaluated to analyze the response of hazelnut explants in culture tubes to bacterial blight inoculation. The bacteria were found to proliferate on the 2016 Corylus media, so explants were transferred to inert media for the duration of the evaluation. Infection symptoms consistent with those seen in the field such as leaf lesions, leaf chlorosis, leaf and shoot necrosis along with characteristic bacterial ooze were observed in inoculated hazelnut explants within two weeks. No significant differences in relative susceptibility of cultivars was detected, as each of the five cultivars displayed symptoms similar in rate and severity over the course of evaluation. Each of the five cultivars had been reported to succumb to bacterial blight infection under field conditions. The in vitro protocol reduced variability due to the environment, and saved considerable space and time compared to conventional pathogen screening using potted trees or field inoculations. Tissue culture as a technique for rapid screening and understanding disease progression and symptomology was demonstrated in bacterial blight susceptible hazelnut cultivars over time.