Preliminary report on the improved resistance towards Pseudomonas syringae pv. actinidiae of cultivated kiwifruit (Actinidia chinensis) when grafted onto wild Actinidia guilinensis rootstock in vitro

The production of kiwifruit around the world is widely affected by the bacterial canker disease caused by Pseudomonas syringae pv. actinidiae (Psa). The use of resistant rootstock is considered to be an effective way to control diseases; however, there are few studies on the evaluation and utilization of Psa-resistant rootstocks in kiwifruit. A genotype Gui-1 in the Actinidia guilinensis species demonstrated strong resistance to Psa in our previous study, so it was used as a rootstock to evaluate its effect on the resistance of the highly susceptible cultivar ‘Hongyang’ (Actinidia chinensis) with an in vitro assay. The results show that Gui-1 significantly improved the resistance of ‘Hongyang’ scion to Psa without affecting the fruit quality, and also showed that the in vitro cane could still maintain the rootstock-induced resistance, but the resistance imparted to the scion by the rootstock might be spatially and temporally uneven. This study first provides the laboratory evidence of grafting-induced resistance to Psa, which provides a foundation for the application of resistant rootstock in kiwifruit production. The study also provides implications for the study of the mechanism of rootstock–scion interaction, especially those related to the resistance to non-soil-borne disease.