Indagine sulla presenza di fitoplasmi in Actinidia spp. in Italia centro-settentrionale

During surveys carried out to monitor the kiwi plants showing severe canker symptoms caused by Pseudomonas syringae pv actinidiae (Psa) phytoplasmas were also detected. Further surveys were then carried out in kiwi plantations located in North and Central Italy. Analyses were carried out on 71 samples collected in Emilia-Romagna, Veneto and Lazio regions from plants showing symptoms of leaf reddening and downward curling and crinkling; the green variety (Hayward) show also leaf reddening while in Jintao (yellow) there was a general plant decline and yellowing of the leaves. Scattered plants also showed other symptoms such as irregular shape of non lignified branches and reddening shoot proliferation from the rootstock. These samples showed negative results for Psa presence, while phytoplasma presence was confirmed in the majority of tested samples. Yellow varieties resulted to be more susceptible than green varieties to phytoplasma presence, resulting positive in the 75% of tested samples. In particular the 25% of positive samples were infected by 16SrI-B (aster yellows), the 11% by 16SrX-A (apple proliferation), the 6% by 16SrXII-A (“stolbur”). Moreover the 11% of the positive samples presented mixed infection by 16SrI+16SrX, the 4% by 16SrX+16SrXII-A, the 2% by 16SrI+16SrXII-A. No studies related to possible vector of phytoplasmas to kiwi plants were carried out, but there is the possibility of infection by micropropagation techniques that are massively used to produce nursery materials for all varieties. These results confirm preliminary reports and further work is in progress to evaluate possible interaction of the two prokaryotes in infected plants and the phytoplasma influence in the epidemic of canker disease.