A. chinensis var. chinensis on A. macrosperma roostock: genotype susceptibility to Pseudomonas syringae pv. actinidiae, the causal agent of kiwifruit bacterial canker

Actinidia spp. production is mainly represented by the species Actinidia chinensis var. deliciosa and var. chinensis which are amongst the most recently domesticated fruit crop species commercially cultivated. Italy, with 25,000 ha, is the world's second largest kiwifruit producer, after China, with the main growing areas in the Regions of Lazio, Piemonte, Emilia Romagna, Veneto and Campania. Nutritionally, the kiwi fruits are exceptionally rich in nutrients (e.g. Vit C, Vit E, K and folate), carotenoids, dietary fiber and bioactive compounds with beneficial properties for metabolism and health. Moreover, kiwifruit is a highly profitable crop with a long shelf life suited to global trade. However, in the last 20 years, Kiwifruit Bacterial Canker (KBC) caused by Pseudomonas syringae pv. actinidiae (Psa, included in the EPPO A2 list) brought about large economic losses in the kiwifruit agri-chain and recently a reduction of 3,000 ha, about 12% of the total area cultivated with kiwifruit in Italy, occurred due to the spread of Kiwifruit Vine Decline Syndrome (KVDS). The latter was observed in different environments and often associated with waterlogging, root rotting/asphyxia. Given the relevance of kiwifruit production worldwide, to employ cultivars resistant to such stresses is the most promising control strategy. In greenhouse, the KBC disease severity was determined in three Actinidia chinensis var. chinensis genotypes on rootstock A. macrosperma (Bounty 71) after foliar spray inoculations with a suspension of the virulent strain Psa IPV-BO 8101, isolated in 2009 from A. chinensis ‘Hort16A’ in the first farm of Emilia-Romagna affected by KBC