Transmission of ‘Candidatus Phytoplasma aurantifoliae’ by Hishimonus phycitis
Lime witches’ broom caused by ‘Candidatus Phytoplasma aurantifoliae’ (EU Annexes) is a devastating disease in Oman, the United Arab Emirates and southern Iran. This disease mainly affects lime (Citrus aurantifolia), but in Iran it also occurs on ‘bakraee’ which is a Citrus reticulata hybrid. The most common phloem-feeding insect associated with lime trees in affected areas is Hishimonus phycitis (Homoptera: Ciccadellidae). ‘Ca. P. aurantifoliae’ has been detected in this insect (ELISA, PCR) but all attempts to demonstrate that H. phycitis is a vector had failed. In May 2006, H. phycitis nymphs and adults were collected in a diseased lime orchard in Minab (Hormozgan Province). More than 100 insect samples were tested and 70% tested positive (PCR). Additional insects were collected from the field and caged with seedlings of ‘bakraee’. After 8 weeks, insects were killed with an insecticide. 6 months after inoculation, 3 plants (out of 10) showed typical symptoms and tested positive in PCR assays. The identity of the phytoplasma was verified by RFLP analysis. This is the first report of natural transmission of ‘Ca. P. aurantifoliae’ by H. phycitis.
Sources
Salehi M, Izadpanah K, Siampour M, Bagheri A, Faghihi SM (2007) Transmission of ‘Candidatus Phytoplasma aurantifolia’ to bakraee (Citrus reticulata hybrid) by feral Hishimonus phycitis leafhoppers in Iran. Plant Disease 91(4) p 466.