Detection of different groups of phytoplasmas in palms species of Puerto Rico

Authors: SIMBAÑA-CARRERA, LORENA - University Of Puerto Rico; RIVERA-VARGAS, LYDIA - University Of Puerto Rico; SEGARRA-CARMONA, ALEJANDRO - University Of Puerto Rico; Serrato Diaz, Luz; CONTALDO, NICOLETTA - University Of Bologna; SATTA, ELEONORA - University Of Bologna; BERTACCINI, ASSUNTA - University Of Bologna

Submitted to: Journal of Agriculture of the University of Puerto Rico
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2024
Publication Date: 7/1/2024
Citation: Simbaña-Carrera, L.L., Rivera-Vargas, L.I., Segarra-Carmona, A.E., Serrato Diaz, L.M., Contaldo, N., Satta, E., Bertaccini, A. 2024. Detection of different groups of phytoplasmas in palms species of Puerto Rico. Journal of Agriculture of the University of Puerto Rico. 102(2)/67-88. https://doi.org/10.46429/jaupr.v108i2.21591.
DOI: https://doi.org/10.46429/jaupr.v108i2.21591

Interpretive Summary: Palm trees play important cultural, ecological, and economic roles in the tropics. However, palms are affected by diseases commonly known as lethal yellowings caused by phytoplasmas being the Coconut Lethal Yellowing (CLY) the most devastating disease of palms worldwide. In Puerto Rico, several palms displayed symptoms such as leaf chlorosis or yellowing, inflorescence and fruit’s necrosis and eventual death. The objective of this study was to identify and characterize phytoplasmas in palms and their potential insect vectors in Puerto Rico. Three transects were designated across the island and 69 palms (Cocos nucifera (n=15), Gaussia attendata (n=1), Leucothrinax morrisii (n=1), Pseudophenix sargentii (n=1), Roystonea borinquena (n=50) and Washingtonia robusta (n=1)) displaying typical phytoplasmas symptoms were sampled. In addition, twelve different insect species (Auchenorrhyncha: Fulgoroidea) that can act as potential phytoplasma vectors were sweep-collected from palms and grasses near the study area. Amplification of the 16S ribosomal region of phytoplasmas and RFLP analyses were used to identify phytoplamas molecularly. Overall, 17 palm samples were positive to phytoplasmas. One in C. nucifera, one L. morrisii and fifteen in R. borinquena. Phytoplasmas detected belong to six different ribosomal groups: 16SrII, 16SrIII, 16SrIV, 16SrVI, 16SrIX and 16SrX. The most common phytoplasma detected (59%) is related to the 16SrII group. Only one insect sample, the cixiid, Haplaxius crudus was positive for a 16SrII-related group phytoplasma, collected from a phytoplasma positive R. borinquena palm. To our knowledge this is the first report of a 16SrII-related group phytoplasmas in R. borinquena in Puerto Rico and worldwide. This study is important because R. borinquena is the most abundant native palm in the island and presence of different ribosomal groups of phytoplasmas is critical to develop an effective control of this disease and its vector.

Technical Abstract: Palm trees play important cultural, ecological, and economic roles in the tropics. Native palm species such as the royal palm, Roystonea borinquena O.F. Cook, is extensively planted in landscapes and urban areas in Hispaniola, Puerto Rico and the Virgin Islands. Worldwide, palms are affected by diseases commonly known as lethal yellowings caused by phytoplasmas. Coconut Lethal Yellowing (CLY) is the most devastating disease of palms caused by a 16SrIV group phytoplasma. Around the island of Puerto Rico palms displayed symptoms such as leaf chlorosis or yellowing, inflorescence and fruit’s necrosis, and eventual death. The objective of this research was to identify and characterize phytoplasmas in palms and their potential insect vectors, emphasizing a native palm, R. borinquena. To fulfill our objective, 69 palms belonging to the species: Cocos nucifera (n=15), Gaussia attendata (n=1), Leucothrinax morrisii (n=1), Pseudophenix sargentii (n=1), Roystonea borinquena (n=50) and Washingtonia robusta (n=1) were sampled within three transects designed across the island. Ninety percent of palms sampled displayed typical phytoplasmas symptoms. In addition, twelve different insect species (Auchenorrhyncha: Fulgoroidea) that can act as potential phytoplasma vectors were sweep-collected from palms and grasses near the study area. The 16S ribosomal region of phytoplasmas was amplified using nested PCR and subjected to RFLP analyses to allow their ribosomal grouping. Overall, 17 palm samples were positive to phytoplasmas. These were C. nucifera (n = 1), L. morrisii (n = 1) and R. borinquena (n = 15). Phytoplasmas detected belong to six different ribosomal groups: 16SrII, 16SrIII, 16SrIV, 16SrVI, 16SrIX and 16SrX. The most common phytoplasma detected (59%) is related to the 16SrII group. Nine royal palms (R. borinquena) and one key thatch palm (L. morrisii) samples were positive to 16SrII-related group. Only one insect sample, the cixiid, Haplaxius crudus was positive for a 16SrII-related group phytoplasma, collected from a phytoplasma positive R. borinquena palm. Another important epidemiological significant finding of the research was the detection of a phytoplasma related to CLY of the 16SrIV group in one individual of R. borinquena. This native species is the most abundant palm in the island. To our knowledge this is the first report of a 16SrII-related group phytoplasmas in R. borinquena in Puerto Rico and the world.