Thermotherapy Treatments of Fruit Trees of the Genus Prunus Infected by Viruses and Bacteria.

The thermotherapy technique has been used to evaluate the viability of hot water treatments (HWTs) for the elimination of different pathogens that infect commercial fruit trees. The present project focuses on common pathogens of Prunus species at the nursery level when external propagation material is needed, which is not always in optimal sanitary conditions. Different combinations of temperature/duration treatments were applied to budwood of nectarines infected by Xanthomonas arboricola pv. pruni (Xap) and almonds infected by Prunus necrotic ringspot virus (PNRSV). These treated buds were then grafted onto disease-free micropropagated rootstocks. In bacteria-infected nectarine tissues treated at 45 °C for 40 min, Xap was not detected in any sample, preserving a high viability of the grafted plants. In virus-infected almond tissues treated at 45 °C for 50 min a few individual plants were identified in which no virus was detected. These results demonstrated the effectiveness of the HWT and suggest that these techniques could be applied at nursery level, on a large scale for the eradication of bacteria or on a small scale for the recovery of virus-free individuals.