Graft incompatibility in chestnut: a multidisciplinary approach for early identification in Castanea spp

Among the key factors aimed at improving fruit production, grafting plays a pivotal role. The rootstock genotype influences crop efficiency and fruit quality, resilience in new ecological scenarios and susceptibility to pests and diseases. In recent years, research on rootstock/scion relationships has been investigated, but graft incompatibility still represents a limit to nursery activities. Research has been concentrating on the role of polyphenols as markers of either compatible or incompatible grafts. Promising results have been achieved on several fruit species such as Vitis spp., Prunus spp. and Pyrus spp., analyzing the qualitative and quantitative expression of phenolic compounds in scion and rootstock. Indeed, different patterns can determine dysfunctions at the graft union, highlighting them as potential markers for graft incompatibility. Moreover, several physiological parameters such as chlorophyll content, fluorescence rate, and stomatal conductance proved to be effective tools in the early detection of physiological stresses related to graft incompatibility. Thus far, very few studies have been carried out on phenolic compounds and physiological response in chestnut (Castanea spp.) grafting. The present work investigated the biochemical mechanisms and the morpho-physiological status of several combinations of Castanea spp. cultivars and rootstocks. The analysis involved inner and outer tissues of chestnut grafts at two phenological stages. Phenol compounds were firstly extracted using green extraction technology (ultrasounds). Separation, identification, and quantification were performed via HPLC. Analysis of physiological aspects was carried out using porometer, chlorophyll content meter, and Arborcheck® instrumentation. The results seem to validate the effectiveness of this multipurpose approach for the prediction of graft incompatibility in chestnut.