Xylella fastidiosa(Xf) can infect a wide range of woody crops that are grown extensively worldwide. The temperature patterns inside the woody plant parts which are the habitat of Xf cells may nevertheless be different to those of the standardly recorded air temperature, due to the wood thermal inertia, wind speed or incident radiation energy andits shading by the canopy. To investigate the relationship between the temperatures that can be reached in different partsof the xylematic system and those of the surrounding air,an experiment was conducted in Córdoba, southern Spain, from 2017 to 2019.In a high-density plot, a set of four mature olive trees (two with maximum exposure to sunlight on the southern border and two in the middle of the plot) were instrumented with a multiplexed set of specially-made thermocouples placed in different parts ofthe active xylem tissues. Measurements were made uninterruptedly from winter 2017 to spring 2019 at 10-min. intervals: inside small branches (1cm diameter), inside the trunk at 2 and 4cm depths,and in the soil underneath the trees at 20cm depth. This set was replicated on the southern (sunlit) and northern side of each tree; insitustandard measurement of air temperature at 1.5m height was also recorded. The experiment was replicated in a nearby almond tree plot. Solar radiation, air temperature and wind speed were measured concurrently in a nearby meteorological station. Our results indicate that winter standard air temperature minimums closely match those of all the above-ground xylematic systems, while maximums may differ substantially (>20°C),especially in the deeper xylem rings. For these parts and the root xylem, a model ofheat transfer which includes the shading effect may be necessary. These results would allow a better parametrisation of epidemiological models used to estimate the development of Xf infection in woody hosts.

Trabajo presentado en la 2nd European conference on Xylella fastidiosa (how research can support solutions), celebrada en Ajaccio el 29 y 30 de octubre de 2019.-- Conferencia invitada

This work has received funding from 727987 XF-ACTORS (EU-H2020), E-RTA2017-00004-C06-02 from AEI-INIA Spain and FEDER, and the Spanish Olive Oil Interprofessional.

Peer reviewed