Phytoplasma detection in declining pistachio orchards in Iran

Pistachio (Pistacia vera L.) is one of the important economic crops in Iran and the reach of high quality with low production cost is an important task for the Iranian pistachio industry. Orchards are mainly obtained by seedlings while also grafting is employed and mainly the Ohadi variety on Badami variety as rootstock is used. Northeastern part of Iran (Khorassan province) is one of the important regions for growing pistachio; this species is known to be tolerant to salts, however Iranian pistachio plantations are on sodic soils and irrigated with low quality, saline water resulting over the recent years in reduction of yields. Decline symptoms such as yellowing of the leaves and reduced vigour in some of the branches were observed in orchard where poor production yield is also reported. Nucleic acid samples from 10 pistachio plants grafted on the Badami rootstok and showing decline symptoms were collected in two different locations Feizabab and Bardaskan (South of Khorassan province) in Iran during spring 2009. Molecular analyses were carried out to verify phytoplasma presence and preliminary identification was achieved by PCR/RFLP analyses on R16F2/R2 amplicons obtained after nested PCR on P1/P7 amplicons. Nine out of the 10 samples were positive in nested-PCR and phytoplasma detected could be affiliated to ribosomal groups 16SrI (‘Candidatus Phytoplasma asteris’ – related), 16SrII (‘Ca. P. aurantifoliae’ - related), 16SrIX (‘Ca. P. foenicium’ - related) and 16SrXII (stolbur-related). Preliminary surveys allow to verify presence of potential phytoplasma vectors such as psyllids and leafhoppers. In particular pistachio psylla (Agonoscena pistaciae) and pistachio leafhopper (Idiocerus stali Fieb) were abundantly present in affected fields. Researches are in progress to clarify epidemiological aspect of the phytoplasma presence and spreading in these Iranian pistachio cultivations.