Multilocus Sequence Analysis Reveals New Hosts of Palm Lethal Decline Phytoplasmas in Florida, U.S.A.

Abstract

Palm-infecting phytoplasmas have been a persistent threat to sustainable palm production in Florida, U.S.A., for nearly a century. First, lethal yellowing (LY) was introduced in the early 1900s, then lethal bronzing (LB) was introduced around 2006. While LY is currently rare in Florida, LB is actively spreading throughout the state and as it becomes more established, has begun infecting new host species. Continual monitoring efforts throughout the state seeks to catch infections and remove palms before further spread. As a result of this effort, many palms displaying a variety of symptoms are sampled and submitted to the University of Florida – Fort Lauderdale Research and Education Center (FLREC) for confirmation of phytoplasma infection status. Over the course of 3 years, multiple samples of Washingtonia robusta and Roystonea regia were submitted. All of these samples were negative for phytoplasma upon the initial qPCR screening and were tested with universal primers and confirmed as negative. Specimens of Arenga engleri, Rhapidophyllum hystrix, and Sabal palmetto were received and tested positive for LB, LB, and LY, respectively, tentatively representing new host records for these species and respective phytoplasma. Multilocus sequence analyses utilizing the 16S rRNA, 16S-23S intergenic spacer region, secA, secY, and groEL further confirmed the identity of LB and LY in the respective new hosts. These results highlight the need for continued monitoring of palms in Florida so that infected palms can be removed quickly. Also, the novel molecular data ( secY) help better understand and identify phytoplasmas in palms.