Lethal yellowing disease of the coconut palms (cocos nucifera l.): An overview of the crises

Abstract

Phytoplasmas are minute cell, wall-less prokaryotes with a diameter less than 1 micrometer ranging from 200 to 800 µm. They have cytoplasma, ribosome and strands of nucleus materials. They arose from gram-positive Clostridium-like bacterial ancestor of the lactobacillus lineage, which appears to have suffered extreme genome reductions when compared with their gram-positive relatives. The inability to culture phytoplasmas in any axenic media and the low concentration in phloem of infected plants are obstacles for efficient diagnosis. Polymerase chain reaction (PCR) amplification is the most important tool for detecting phytoplasmas in plant and insect hosts. Real-time PCR method has so many advantages over the conventional PCR. Recent reports across coconut growing regions tell increase in the incidence of lethal yellowing disease (LYD). Palms with greater than 25% leaf discoloration due to LYD should be removed. Fields replanted with the tolerant varieties must be monitored using molecular technique. The overview crises of more than 100 years after the incidence of phytoplasmas and more than 50 years of research efforts to control LYD of coconut palms world wide are presented. Key word: Polymerase chain reaction and lethal yellowing disease.