PHYTOPLASMAS ASSOCIATED WITH DATE PALM IN THE CONTINENTAL USA: THREE 16SRIV SUBGROUPS
Keywords:Phoenix dactylifera, date palm, phytoplasma, subgroup 16SrIV-A, subgroup 16SrIV-D
Only one major group of phytoplasmas, namely group 16SrIV, has been identified in date palms in the continental United States, and only in the states of Florida and Texas where date palms are used for aesthetic purposes in the landscape and not for date production. While strains belonging to three 16SrIV group have been detected in Florida date palms (16SrIV-A, 16SrIV-D and 16SrIV-F), only subgroup 16SrIV-D strains have been detected in Texas date palms. The subgroup 16SrIV-D phytoplasmas identified in Florida and Texas appear to be genetically the same. Field symptoms caused by this group of phytoplasmas in date palms is described, along with the molecular techniques used to detect the phytoplasma in palm tissue and to identify the subgroup detected. Preventive management in the landscape is based on use of resistant palm material and liquid trunk injection of the antibiotic oxytetracycline HCl into susceptible palms.