Effects of hot water treatment to control Xanthomonas arboricola pv. corylina on hazelnut (Corylus avellana L.) propagative material

- Hot water treatments significantly reduced Xanthomonas arboricola pv. corylina in hazelnut buds.
- 42 °C for 45 min was the optimal combination to guarantee the safe development of the plant.
- Plant mortality was significantly higher for the suckers treated at temperatures higher than 46 °C.
- Principal component analysis indicated Tonda Gentile delle Langhe as the most sensitive cultivar to the higher temperature.
- This technique could be applied for the sanitation of hazelnut nursery propagative material.

Bacterial blight, caused by Xanthomonas arboricola pv. corylina, is a major disease of hazelnut (Corylus avellana L.) that affects mainly nurseries and young orchards by causing significant plant mortality. To prevent or reduce the occurrence and spread of this disease in new plantations it is fundamental to grow suckers that are free of this pathogen. In this study, hot water treatments were applied to hazelnut propagative materials of six cultivars, namely, Tonda Gentile delle Langhe, Tonda Gentile Romana, Tonda di Giffoni, Mortarella, Camponica and San Giovanni by assessing four different combinations of temperature (42 °C, 46 °C and 50 °C) and duration (30 and 45 min). The heat treatment significantly reduced the presence of this pathogen in the bud of all of the hazelnut suckers and no sign of infection was observed in the year following the treatment. In the first season after heat treatment, plant mortality was significantly higher for the suckers that were treated at temperatures higher than 46 °C, with Tonda Gentile delle Langhe and Tonda Gentile Romana having only 38% and 7%, respectively, of plants alive at the end of the season. The development of shoot growth and stem diameter was significantly influenced by the treatments only during the first year, with the cultivar being the only factor significantly affecting development in the second year of growth. A principal component analysis indicated that Tonda Gentile delle Langhe was the most sensitive cultivar to the different hot water treatment regarding both the vegetative growth and the mortality of the plants. Statistical analysis suggested that this technique could be applied for the management of hazelnut nursery stock to decrease the risk of X. a. pv. corylina spreading. In particular, 42 °C for 45 min was the optimal combination to guarantee the safe development of the plant with a very low risk of pathogen spreading.