Changes observed in Pritchardia pacifica palms affected by a lethal yellowing-type disease in Mexico

Lethal yellowing (LY) is a devastating disease, affecting more than 35 palm species. One of them, Pritchardia pacifica, was found to be very susceptible in Florida and it is affected by a LY-type syndrome in Yucatan, Mexico. In this study, plants of P. pacifica were exposed naturally to feral insects in an area affected by LY in Mexico. All the plants exposed died showing symptoms of leaf decay with death occurring within approximately four months after first symptom. Real-time (polymerase chain reaction) PCR analysis of DNA extracts for phytoplasma detection and in silico sequence analysis of nested-PCR amplicons showed an association with 16SrIV-D phytoplasmas in plants studied. Time-course changes were studied for the detection of phytoplasmas, stomatal conductance and leaf temperature by thermography. One month before appearance of the first symptom, changes in all the parameters were observed: positive detection of phytoplasma DNA, a reduction in stomatal conductance that is complete and irreversible, and the appearance of a peak in leaf temperature. These results provide insights into a better understanding of this disease in P. pacifica. Moreover, from a practical point of view, the changes described could be useful for developing methods for early detection of the disease. Key words: Lethal yellowing-type disease, phytoplasmas, Pritchardia pacifica, stomatal conductance, thermography.