The issue
Phytoplasmas are plant bacterial pathogens of agriculturally important plants including palm species. Phytoplasmas of coconut are associated with lethal yellowing diseases and have been responsible for the death of vast areas of palms in the coastal regions of west and east Africa and the collapse of the coconut industry in Ghana.
Currently, the most appropriate management options for control of phytoplasmas in coconut is the rapid removal and burning of infected palms, followed by the replanting with healthy palms. An important factor in the success of this strategy is the quick detection of phytoplasma infections, so that they can be removed, before they have had a chance to spread. A rapid in-field diagnostic test is required to help combat infections.
The research
Plant pathologists at Nottingham developed a loop mediated isothermal amplification (LAMP) DNA assay for the detection of a range of pathogens, including phytoplasma diseases of coconut. The LAMP diagnostic assay was shown to be much quicker than conventional Polymerase Chain Reaction (PCR) and could work on relatively impure DNA extracted using a simple method with minimal equipment. For the detection of phytoplasmas of coconut, LAMP primers were designed specifically to detect the pathosystem most prevalent in west Africa.
Testing of the LAMP diagnostic assay in Ghana showed phyoplasmas infecting coconut could be accurately detected using small amounts of trunk samples within 20 minutes. The rapid in-field diagnostic test was validated using the same and additional samples in the University of Nottingham laboratories as part of the EU funded TROPICSAFE project.
The impact
Previous methods for the detection of phytoplasmas of coconut has required samples of trunk to be transported to laboratories for DNA extraction and testing by conventional PCR and gel electrophoresis, or by real-time PCR. Because of the remoteness of some diseased areas, particularly in sub-Saharan Africa, this can often take two or more days from sampling to final results.
The rapid LAMP diagnostic test developed can be deployed in the field, using reagents stable at ambient temperatures, a portable battery operated machine and minimal other equipment. The rapid in-field diagnostic test is helping to combat lethal yellowing disease of coconut and support the livelihoods of small holder farmers in Africa that rely on coconut for income.
The Director of CSIR Oil Palm Research - Ghana said ‟The LAMP assays are revolutionising diagnosis of lethal disease in Ghana and helping us to do so much more than we could do with the traditional methods.”