An Experimental Inoculation System to Study Citrus-Xylella fastidiosa Interactions

Area of Science:

• Plant Pathology
• Bacteriology

Background:

• Citrus variegated chlorosis (CVC) is a significant citrus disease.
• Reproducing CVC symptoms experimentally has been difficult, hindering research.

Purpose of the Study:

• To optimize methods for reliably reproducing CVC symptoms in experimental plants.
• To identify effective inoculation techniques and plant ages for CVC studies.

Main Methods:

• Sweet orange (Citrus sinensis) cultivars were inoculated with Xylella fastidiosa (CVC strain 9a5c).
• Inoculation methods included root immersion, stem absorption, pricking, and infiltration on plants of varying ages.
• Plants were grown in pots or foam trays, with samples collected for PCR and bacterial isolation.

Main Results:

• Root immersion and stem inoculation of older plants yielded low CVC symptom and isolation rates (0-9%).
• Stem pricking or injection of 1-month-old seedlings resulted in high CVC symptom (29-90%) and isolation rates (26-98%).
• Foam trays led to reduced growth, shorter incubation, and higher disease severity compared to pots.

Conclusions:

• Stem pricking or injection of young seedlings is an effective method for inducing CVC symptoms.
• Using foam trays enhances experimental reproducibility and efficiency for CVC research.