Clove-transmissibility of Pseudomonas salomonii, the causal agent of ‘Café au lait’ disease of garlic

Abstract

Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial disease, known as ‘Cafe au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources such as crop debris, soil or alternate hosts in order to develop successful control strategies.