Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2008
Publication Date: 6/11/2008
Citation: Montero-Astua, M., Saborio-R, G., Chacon-Diaz, C., Villalobos, W., Moreira, L., Rivera, C., Hartung, J.S. 2008. First report of Xylella fastidiosa in Avocado. Plant Disease. 92(1):175. Interpretive Summary: Avocado is an important fruit crop in Costa Rica. Over the last 10 years trees have shown symptoms of a new disease, including a leaf mottle and scorch, defoliation, shortened branches and eventually death of branches. We tested these diseased trees for the presence of the bacterial pathogen Xylella fastidiosa using both serological and DNA based assays. The results of these tests indicated that symptomatic trees are infected by Xylella fastidiosa. Electron microscopy was used to examine leaf tissue and the bacterium was found in symptomatic, but not non symptomatic tissues. The pathogen is apparently closely related to a strain of the same pathogen found in grapevines in California, and less related to a strain of the pathogen from sweet orange in Brazil. This is the first report of Xylella fastidiosa in avocado trees and this is likely to be the cause of the observed disease symptoms. This work will be of interest to avocado growers, regulatory officials and scientists interested in the many diseases caused by Xylella fastidiosa.
Technical Abstract: Since the late 1990s, chlorotic mottling, marginal scorch, deformation of leaves, defoliation, shortening of internodes, and branch dieback have been observed in avocado trees (Persea americana Mill.) in Costa Rica. The symptoms are not uniformly distributed in the tree, so some branches of a tree are symptomatic, while others are not. These symptoms are similar to several leaf scorch diseases caused by the bacterium Xylella fastidiosa Wells (2,4). Two hundred twenty seven avocado trees were tested by enzyme-linked immunosorbent assay (ELISA) with commercial antibodies against X. fastidiosa (Agdia, Elkhart, IN) from 2000 to 2004 and 188 were ELISA positive.