ARS | Publication request: Irrigation water is an unlikely source of inoculum of Pseudomonas cannabina pv. alisalensis

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 6, 2010
Publication Date: August 2, 2010
Citation: Mauzey, S.J., Bull, C.T. 2010. Irrigation water is an unlikely source of inoculum of Pseudomonas cannabina pv. alisalensis. Phytopathology 100:579.

Technical Abstract: Pseudomonas cannabina pv. alisalensis causes severe bacterial blight on crucifers across the United States. These experiments examined the potential of irrigation water as a source of inoculum for P. cannabina pv. alisalensis. Water samples were collected from multiple irrigation reservoirs and sprinklers near infected fields. The samples were tested for the presence of P. cannabina pv. alisalensis using PCR for detection of coronatine and ethylene biosynthesis genes. P. cannabina pv. alisalensis was not detected in irrigation water samples, however the limit of detection using these methods was high. Survival in water was modeled using a rifampicin resistant strain of P. cannabina pv. alisalensis and enumeration on antibiotic containing media. Population levels of P. cannabina pv. alisalensis added to irrigation water dropped significantly within the first few days after inoculation. On average P. cannabina pv. alisalensis populations dropped from 5.5 log (CFU/ml) at inoculation to below 2.0 log (CFU/ml) after one week. Additionally, the relationship between population levels of P. cannabina pv. alisalensis spray inoculated onto broccoli raab (Brassica rapa subsp. rapa) and the resulting level of disease was evaluated. Under greenhouse conditions populations of P. cannabina pv. alisalensis as low as 2.0 log (CFU/ml) resulted in disease. These results indicate that irrigation water is an unlikely source of inoculum for P. cannabina pv. alisalensis on crucifers.