Testing Actinidia chinensis (kiwi) for susceptibility to plant virus infections.

The susceptibility of Actinidia chinensis Planch. ( K i w i ) t o some of the most comrnon viruses in Italy has been studied under glass-house conditions by mechanical inoculation and aphid transmission. Five t o 12 kiwi plants at the four-leaf stage have been inoculated with each of the following viruses: alfalfa mosaic ; Amaranthus leaf mottle, bean yellow mosaic and potato Y (Potyvirus group); cucumber mosaic (CMV) (Cucumovirus); grapevine fanleaf and grapevine chrome mosaic (Nepovirus); grapevine virus A (Closterovirus) ; poplar mosaic (Carlavirus) ; tomato bushy stunt and petunia asteroid mosaic (Tombusvirus); tobacco mosaic and tomato mosaic (Tobamovirus); tobacco necrosis (TNV); tobacco rattle (TRV) (Tobravirus) . Kiwi plants reacted with continuously growing necrotic lesions to inoculations with TNV and TRV. Both viruses were recovered by back inoculation to indicator plants from necrotic tissues only, but not from uninoculate d leaves. Kiwi plants , mechanically inoculated with CMV, showed leaf chlorosis and reduced growth, reminescent of Fe deficiency and unbalanced P/Fe ratio symptoms (as reported in literature). However, CMV was recovered (with difficulty) from chorotic kiwi tissues by sap inoculation t o " White Burley " tobacco whereas preliminary attempts to vector CMV from kiwi to kiwi using the green peach aphid (Myzus persicae Sultz . ) failed . The difficulty of recovering the virus by back inoculation could possibly explain the absence of reports on virus infections in kiwi plants . Moreover, nothing is known from literature on virus diseases of Actinidia spp. and very little on the ones of Guttiferae, the family to which Actinidia genus belongs. This may indicate a scarce susceptibility of the whole family t o viruses. Experimental data on kiwi show low susceptibility of this species to virus infections, weak display of symptoms and the presence of some sap component which causes difficulties in the recovery of viruses.