Possibile interazione fra presenza di fitoplasmi e di Pseudomonas syringae pv. actinidiae in piante di kiwi.

After detection of phytoplasmas in young cuttings of kiwifruit showing reddening of the leaves the presence of these prokaryotes was verified in some orchard having severe canker disease symptoms. In some cases the presence of diverse phytoplasmas in mixed infection with Pseudomonas sysringae pv. actinidiae (Psa) was detected. Surveys were therefore carried out in kiwi plantations located in North and Central Italy to verify the presence of phytoplasmas in Psa infected kiwi orchards. Samples from 72 kiwi trees were collected from Actidinida chinensis and A. deliciosa. Phytoplasma infected plants showed in some of the branches a premature reddening of leaves downward curled and crinkling; the green variety show also leaf reddening. These samples showed negative results for Psa presence while phytoplasmas belonging to groups 16SrI, 16SrXII and 16SrX were identified in single or in mixed infection after RFLP analyses of generic or specific amplicons from 16S rDNA. The phytoplasmas were present in diverse combinations in all the tested orchards in 68% of tested plants. The group more often identified was aster yellows (16SrI) (26%) followed by the mixed infection of aster yellows and apple proliferation (16SrX) groups (11%) or by apple proliferation (10%).