ARS | Publication request: Evaluation of pathogenicity and insect transmission of Xylella fastidiosa strains to olive plants

Submitted to: California Olive Committee Annual Research Report
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2010
Publication Date: March 30, 2010
Citation: Krugner, R. 2010. Evaluation of pathogenicity and insect transmission of Xylella fastidiosa strains to olive plants [abstract]. California Olive Committee Annual Research Report. P. 48-56.

Technical Abstract: Xylella fastidiosa (Xf) is a xylem-limited bacterium that causes disease in a number of economically important crops in California and worldwide. Newly observed scorching symptoms in olive trees may be due to Xf infection. If true, “olive leaf scorch disease” (OLSD) would represent a new threat to the olive industry in California. To assess this possibility, the role of Xf as the causal agent of OLSD was investigated. Samples from 90 olive plants showing branch dieback and leaf scorch symptoms were collected to determine if Xf was associated with presence of disease symptoms. Polymerase Chain Reaction (PCR) and isolation detected Xf in 23 samples, from which three strains were isolated. Four-primer DNA analysis indicated that Xf in all positive samples had the A genotype. This genotype causes almond and oleander leaf scorch diseases, but not Pierce’s disease in grapevines. Healthy olive plants were needle-inoculated with bacterial cells from laboratory cultures and rated for symptom development every two weeks for a year. Symptom development in needle-inoculated plants was variable. Consequently, the status of Xf as the causal agent of OLSD remains unresolved.