Survival and dispersal of Xanthomonas citri pv. citri from infected Satsuma mandarin fruit

Xanthomonas citri pv. citri was not detected by PCR in aqueous sonicates from 3491 mature, asymptomatic fruit harvested from severely diseased Satsuma mandarin trees growing in Saga city, Japan. No strains of X citri pv. citri were recovered from the fruit in either 2005 or 2006. Thus it is unlikely that healthy, asymptomatic Satsuma mandarin fruits harbour detectable populations of X. citri pv. cirri. The survival of X. citri pv. citri on Satsuma mandarin fruits discarded in an orchard was determined in two consecutive years. Bacterial numbers on the contaminated fruits decreased significantly in the first 3 d after fruits were discarded. Using a PCR technique to detect the bacterium, there was no detectable spread of X. citri pv. citri from contaminated fruit into rainwater collected beneath the fruit. The results of this investigation demonstrate that populations of X. citri pv. citri present in contaminated fruit were not transferred to susceptible hosts, even when the fruits were placed in close proximity to hosts that were in a receptive stage. There was no spread of X. citri pv. citri in this study, indicating that there is a low risk transmission of this bacterium. (C) 2008 Elsevier Ltd. All rights reserved.