Detection and identification of lethal yellowing phytoplasma 16SrIV-A and D associated with Adonidia merrillii palms in Mexico

Adonidia merrillii is a palm species native to the Philippines and commonly known as the manila palm. Lethal yellowing-type symptoms were first observed for the manila palm in Florida, USA. Manila palms in Mexico have not been reported to carry the lethal yellowing-type phytoplasma and moreover we have documented other symptoms that are not commonly associated to lethal yellowing (LY) disease. Therefore, our objective was to use molecular techniques to identify and characterize the presence of phytoplasmas in manila palms from southeastern Mexico. Thirty-three manila palm plants were analyzed. In general, three syndromes were observed: mature leaf browning, spear leaf necrosis and spear leaf opening. The presence of phytoplasma DNA was detected by nested-PCR using universal and LY-specific primers. Of the 33 palms analyzed, 24 (73%) were positive for the presence of phytoplasmas using universal primers, and 18 (55%) were positive for phytoplasma DNA using the LY-specific primers. By a TaqMan/real-time PCR assay for LY detection, 82% of palms tested were positive for LY-specific phytoplasma DNA. The restriction enzyme profiles of the DNA tested showed two clear patterns. One pattern was similar to that of the phytoplasma 16SrIV-A strain associated with coconut LY, and the other corresponded to the Pritchardia pacifica 16SrIV-D strain. The 16SrIV-A strain is associated with mature leaf-browning syndrome. The palms infected with the 16Sr-IV-D phytoplasma exhibited spear leaf necrosis and opening. This is the first report of two phytoplasma strains belonging to the subgroups 16SrIV-A and 16SrIV-D in manila palms.