Dealing with Lethal Yellowing and Related Diseases in Coconut

Abstract

The coconut is a palm of economic and social importance; it is cultivated in 90 countries around the world and the markets of some of its products have been growing exponentially, representing a very promising future for the coconut cultivation and industry. Unfortunately, this is threatened by decreased fruit production due to ageing palms and lethal yellowing (LY) and related phytoplasma diseases (LYDs) that have been devastating coconut palms, particularly in countries of Latin America and the Caribbean (LAC), and Africa, although such diseases are also present in countries in Asia and Oceania. Much research has been carried out to understand LY and LYDs, and associated phytoplasmas have been identified. There are about 16 different strains within nine 16Sr phytoplasma groups. The more diverse group so far is the 16SrIV group, present in countries in the Americas, but also reported in Asia and Oceania. A search of vectors has resulted in one confirmed case in the Americas, a leafhopper (Haplaxius crudus Van Duzee, 1907), and other candidates have been identified but yet to be confirmed. Fifty palm species (including coconut) and 14 non-palm species have been reported as phytoplasma hosts. Screening for resistance has identified resistant germplasm in the Americas which has been used for replanting programs, and similar efforts are being conducted in other parts of the world. Methods for detection and diagnosis have been developed using PCR techniques. Micropropagation has been developed for massive propagation of the selected coconut germplasm. Management practices based on the above are currently being applied. However, even with all the progress achieved, there is still a lot to be done in order to move forward in how to deal more effectively with LY and LYDs. For this purpose, it is very important that research is carried out based on a global strategy, working worldwide in an organized and coordinated fashion, in collaboration with organizations such as ICC and COGENT.