Detection of phytoplasma in plant and insect hosts causing Lethal Yellow and Texas Phoenix Palm decline in Florida

Lethal Yellow (LY) and Texas Phoenix Palm Decline (TPPD) are two different phytoplasmic diseases that have severely impacted the agricultural and ornamental palm species in Florida. Phytoplasma are bacteria lacking a cell wall that are transmitted to naïve plant hosts via phloem feeding insects such as leafhoppers (Cicadellidae) and planthoppers (Fulgoridae). From these there have been several possible insect vectors in Florida such as Haplaxius crudus (Cixiidae), Ormenaria rufifascia (Flatidae), and Omolicna joi (Derbidae). In most places where these pathogens occur the vector complex has not yet been identified due to the difficulties of isolating phytoplasma DNA. Because of its low abundance in plants and its phloem-limited location, management of this disease is extremely challenging. In this study, 18 symptomatic palm core samples from Florida were collected and DNA extracted using DNEasy plant kits. Insect samples were obtained from several corresponding symptomatic palms resulting in a total of 470 insects. DNA was extracted using CTAB extraction protocol and followed by Nested PCR employing LY group-specific 16S rRNA primer pair LY16Sf2/LY16-23Sr2, then visualized on agarose gels. Phytoplasma presence was confirmed in a total of 13 core samples and 16 insects: seven Haplaxius crudus, six Ormenaria rufifascia, and three Omolicna joi. The presence of phytoplasma in the various insect samples does not confirm positive insect transmission; however, it does provide an opportunity for future research to focus on these potential vectors in more detailed transmission studies. Attempts are currently being made to generate a more specific detection method for the phytoplasma pathogen.