APPLE PROLIFERATION TRANSMISSION BY GRAFTING IN DIFFERENT PERIODS OF THE YEAR
The colonisation of Candidatus Phytoplasma mali within the aerial parts of apple trees shows seasonal variations during the year. The presence of the phytoplasma is highest from summer until winter and ranges from very low titres to complete absence in spring. Vegetative propagation by grafting is the standard way of commercial production of planting material; however, it represents an important way of the spread of the disease, if latently infected material is used. It is, therefore, of great importance to evaluate the efficiency of phytoplasma transmission by grafting in different periods of the year. Each month, from March to August 2003, groups of 25 apple plants Golden Delicious were inoculated by double chip budding with scions collected randomly from five different branches of two apple proliferation (AP) infected apple trees Golden Delicious. Five repetitions were done for each branch. The total number of grafted plants amounted to 350. A control of visual symptoms and ELISA were performed in November 2003 and 2004. Data showed that the diffusion of the pathogen in the plant requires time: the percentage of infected plants increased during the second year (2.0% in 2003 to 9.7% in 2004). The success of transmission of the disease varied depending on the period of scion collection. No transmission or very low transmission rates (00.08%) were found between March and May, while it was relevant between June and August (1230%). These results are in agreement with the seasonal distribution pattern of the phytoplasma as analysed by DAPI staining and epifluorescence microscopy. Therefore, it is possible to conclude that the most suitable period for the collection of scions is springtime, when the probability of AP-transmission by grafting is the lowest.
Pedrazzoli, F., Filippi, M., Deromedi, M., Bragagna, P., Battocletti, I., Bianchedi, P.L., Ciccotti, A.M. and Stoppa, G. (2008). APPLE PROLIFERATION TRANSMISSION BY GRAFTING IN DIFFERENT PERIODS OF THE YEAR. Acta Hortic. 781, 489-494
Malus domestica, Candidatus Phytoplasma mali, chip budding, infection, latency