First report of the presence of Pantoea citrea, causal agent of pink disease, in pineapple fields grown in Mexico

Pink disease diminishes the quality of commercially processed pineapple. When heated during the canning process, infected fruit produce an undesirable brown pigment; this may diffuse to healthy products. Pathogenicity tests in vitro, pigment production and slice pigmentation (Coplin & Kado, 2001), have shown that Pantoea citrea is the causal agent of pink disease (Cha et al., 1997).

Pineapple fruits cv. Smooth Cayenne growing in fields of the Cuenca del Papaloapan region (Oaxaca and Veracruz states) of Mexico, were randomly sampled in June 2003. From 11 fields nine bacterial creamy isolates showing a pale yellow colour, were recovered from the interior of visually intact fruits on LB agar plates containing 1% casein peptone, 0.5% yeast extract and 0.5% NaCl. These isolates were positively identified as Pantoea spp. according to 16S rDNA restriction analysis with the endonucleases MspI, MvnI, Tru9A, AluI and HaeIII. These isolates were Gram-, sucrose-, adonitol-, gelatinase-, arginine dehydrolase-, lysine-decarboxylase-, ornitine decarboxylase-, citrate-, H2S production-, urease-, trytophane- deaminase, indole production- and mobility-negative; and glucose dehydrogenase-, acetoin production-, arabinose- and melibiose-positive; conforming to the characteristics of P. citrea. Pathogenicity of P. citrea was demonstrated in a hypersensitivity test developed in this laboratory. When inoculated into tobacco leaves cvs Virginia and Burley the nine isolates assessed produced positive hypersensitive reactions after three days, and the inoculated bacteria were reisolated from the lesions. Pantoea citrea has been found in pineapple cultivated in several countries, but to our knowledge this is the first report of its isolation from pineapple growing in Mexico.

Grants CONACYT 36111-N; VIEP 182-04/NAT/I, and 13/G/NAT/05; and CONCYTEP. We thank L. Rebolledo (INIFAP) for his advice in sampling pineapples, and Michael Dunn (UNAM) for English corrections.