Studies on Pantoea citrea, the Causal Agent of Pink Disease of Pineapple

The causal agent of pink disease of pineapple has been identified as Pantoea citrea, a member of the Enterobacteriaceae. Comparative physiological and biochemical analyses demonstrated that P. citrea isolated from diseased pineapple fruit in the Philippines possesses features identical to those of an American Type Culture Collection type strain of P. citrea and not to those of P. ananas, P. herbicota (formerly Erwinia herbicola), and P. stewartii (formerly Erwinia stewartii). P. cilrea induces the production of compounds in pineapple which become pink to reddish-brown upon cooking the fruit, pulp, or juice. This distinct colour is not induced by Escherichia coli, Agrobacterium tumefaciens, Burkholderia gladioli, Pseudomonas fluorescens, Gluconobacter oxydans, Acetobacter aceti, and Acinetobacter calcoaceticus. Like other well characterized bacteria pathogens, such as Pseudomonas syringae pv. phaseolicola, P. citrea elicits the hypersensitive response (HR) in tobacco. By contrast, G. oxydans and A. aceti that have been previously implicated as the causal agents of pink disease, do not elicit HR. Although the nature of the pink colour in pineapple produced by P. citrea has not been elucidated, the locus conferring this activity has been located on its chromosome. The pink colour can be restored in an avirulent, pink colour defective mutant strain, CMC6, by complementation in trans with a specific 3.8 kb genomic DNA fragment of P. citrea. This suggests that P. citrea contains the genetic elements that are required for pink disease