Molecular studies confirm the presence of ‘Candidatus Liberibacter asiaticus’ in Pakistan
Citrus decline is widespread throughout Pakistan and is attributed to various abiotic and biotic reasons. However, it is suspected that the main cause of citrus decline is due to huanglongbing (greening) which is induced by a bacterium ‘Candidatus Liberibacter asiaticus’ (EPPO A1 List) and transmitted by Diaphorina citri (Homoptera: Aphalaridae - EPPO A1 List). The disease occurs in the nearby Indian provinces of Jammu, Kashmir, Punjab and Rajasthan. In Pakistan, the disease is considered present in Punjab Province and Peshawar (North-West Frontier Province) essentially on the basis of symptomatology. In recent studies, leaf samples were collected from symptomatic citrus trees in orchards at Rabaat, Temurgrah and Peshawar (North-West Frontier Province) and tested by PCR. Results confirmed the presence of ‘Ca. L. asiaticus’ in most tested samples. The bacterium was also detected in Diaphorina citri specimens collected near infected trees at Rabaat. For confirmation, amplicons obtained from leaves and psyllids were sequenced and found identical with a previously published sequence of ‘Ca. L. asiaticus’. These results confirm the occurrence of ‘Ca. L. asiaticus’ in the North-West Frontier Province of Pakistan, but more studies are needed to better determine the extent of the disease within the country.
Chohan SN, Qamar R, Sadiq I, Azam M, Holford P, Beattie A (2007) Molecular evidence for the presence of huanglongbing in Pakistan. Australasian Plant Disease Notes 2, 37-38 (available online: http://www.publish.csiro.au/journals/apdn/)