Study of the biochemical and physiological dynamics occurring during grafting: a further step towards the prediction of graft incompatibility in chestnut

In the last decades many chestnut hybrid rootstocks have been selected according to their adaptation to adverse climatic conditions ant to their resistance to diseases. The main issue that limits their spread is represented by the graft incompatibility. As grafting is the most used propagation technique on Castanea spp., it is essential to find techniques able to early predict disaffinity. Phytochemical and physiological techniques have been tested in this regard with effective results on different fruit species. The present work analysed the total phenol content and the physiological response to grafting in several chestnut combinations, testing different rootstocks. The quantification of phenol compounds from plant samples was performed via spectrophotometer, preceded by a double extraction with solvent and ultrasound-assisted extractor. Stomatal conductance and leaf chlorophyll content were measured during the vegetative cycle. The final goal was to find one or more techniques suitable to early predict grafting incompatibility, the main issue connected to chestnut breeding improvement. The monitoring of chlorophyll content and stomatal conductance allowed to discriminate between the grafting combinations, showing lower values for both the parameters in the case of incompatible combinations. The quantification of the total phenol compounds confirmed previous works on different fruit species, showing higher amounts in incompatible combinations at the end of the vegetative cycle (EVC). The combined study of these parameters contributed to acquiring greater insight into the graft incompatibility matter.