Phytoplasma detection and identification in kiwi plants and possible correlation with Pseudomonas syringae pv actinidiae presence

Surveys were carried out during 2011 and 2012 in kiwi plantations located in North and Central Italy to verify the presence of phytoplasmas in Pseudomonas syringae pv actinidiae infected kiwi orchards. Samples from 72 kiwi trees were collected in 2011 and 2012 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%). Further work is in progress to verify economic impact of phytoplasma diseases in kiwifruits.