First report of Pseudomonas cichorii on Turmeric (Curcuma longa) in Brazil

In 2002 a serious leaf blight was observed on turmeric plants grown for bulb multiplication in an experimental field at the Faculdade de Ciências Agronômicas, in Botucatu, State of São Paulo, Brazil. Affected leaves had irregular lesions that later enlarged and coalesced, resulting in part or whole leaf desiccation. Microscopic examination of tissue sections through lesion margins in sterile water revealed bacterial streaming. A mucoid, white bacterium was consistently isolated on King's B medium (King et al. 1954). A single pure culture of the bacterium was examined and was found to be a Gram-negative, rod-shaped, aerobic, oxidase and catalase positive, fluorescent bacterium, that utilised asparagine and did not produce a hypersensitive reaction on tobacco leaves (Lelliot & Stead, 1987).

The strain was analysed with the MicroLog2 System^® (Biolog, Hayward, USA) and identified as Pseudomonas cichorii with similarity index of 84.2% and a probability of 100%. Leaves of eight week old plants of cv. Açafrão do Norte were inoculated using a toothpick dipped in a bacterial suspension (10⁸ CFU per ml). Control plants were inoculated with water. Disease symptoms were observed on leaves five days after inoculation and the inoculated bacterium was re-isolated from lesions. Control plants remained disease free. Turmeric is not reported as host of P. cichorii (Bradbury, 1986). In Brazil this bacterium has previously been reported to cause disease on several cultivated plants (Marques et al., 1994) but this is the first report on turmeric.