A PHYTOPLASMA IS ASSOCIATED WITH THE WELIGAMA COCONUT LEAF WILT DISEASE IN SRI LANKA

L. Perera, M.K. Meegahakumbura, H.R.T. Wijesekara, W.B.S. Fernando, M.J. Dickinson

Abstract


Coconut palm (Cocos nucifera), is a major and economically important plantation crop widely cultivated in Sri Lanka. A sudden outbreak of a rapidly spreading non-lethal syndrome was first reported in coconut palms from southern Sri Lanka in 2006. This syndrome was named Weligama coconut leaf wilt disease (WCLWD) as it occurred in the Weligama area. WCLWD symptoms are flaccidity and marginal necrosis of leaflets and intense yellowing of the fronds, similar to the Kerala wilt disease of coconut in India. As the disease progresses the crown becomes smaller, the trunk begins to taper and the palm becomes unproductive. Abiotic factors and extra-cellular pathogens were discarded as the cause of WCLWD. Considering that a phytoplasma was previously associated with Kerala wilt disease, the possible phytoplasma aetiology of WCLWD was investigated. DNA extracted from midribs of spear leaves was subjected to nested PCR with phytoplasma universal primers R16F2n/R16R2 and R16mF2/R16R2 nested with fU5/rU3; P1/P7 nested with Chrfor/rU3; and direct PCR with Pc399/P1694. PCR products of expected sizes were obtained from diseased but not from healthy palms from a disease-free area. The sequences generated from the PCR products were submitted to similarity search (BlastN) in the NCBI database which confirmed that a phytoplasma belonging to the 16SrXI ‘Candidatus Phytoplasma oryzae’ group is associated with WCLWD. The phytoplasma was found to be highly similar but not identical to Sugarcane white leaf phytoplasma (99%), Sugarcane grassy shoot phytoplasma (99%) and Kerala wilt phytoplasma (99%).

Keywords


Cocos nucifera; nested PCR; sequencing; detection

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DOI: http://dx.doi.org/10.4454/jpp.fa.2012.009

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