Gliricidia Little Leaf Disease in Costa Rica.

Abstract

Gliricidia sepium is a multipurpose, legume tree species native to Central America and Mexico with wide social and economic importance. Gliricidia little leaf disease (GLLD) is associated with infection by a phytoplasma and is manifested by one or more symptoms, including leaflet yellowing, leaflet size reduction, shortened internodes, and shoot proliferation, often leading to branch die-back or death of young trees. Trees with symptoms were seen in fences and natural stands in the Nicoya Peninsular and on road sides west of San Jose, Costa Rica. Shoot samples were collected from eight symptom-bearing trees in different locations and from two healthy-looking trees in the southeast where no GLLD symptoms were observed. DNA from each sample was used as template in polymerase chain reaction (PCR) with universal phytoplasma rRNA gene primers P1 and P7 (1). DNA from a GLLD-infected tree from Honduras, and a pigeon pea witches'-broom infected Cajanus cajan from Florida, served as positive controls, while DNA from healthy G. sepium and C. cajan seedlings were used as negative controls. A 1.8-kb PCR product, indicative of presence of phytoplasma DNA, was amplified from all symptom-bearing tree samples and positive control DNAs, but not from DNA from the apparently healthy trees or seedlings. Restriction fragment length pattern analysis of PCR products with a range of endonucleases showed no difference between the Honduran and Costa Rican phytoplasma isolates. The distribution and symptom types observed in Costa Rica suggest that GLLD has recently arrived from Nicaragua and is spreading southeast. Reference: (1) L. Kenyon et al. Plant Pathol. 47:671, 1998.