STUDIES ON PANTOEA-CITREA, THE CAUSAL AGENT OF PINK DISEASE OF PINEAPPLE

The causal agent of pink disease of pineapple has been identified as P antoea citrea, a member of the Enterobacteriaceae. Comparative physiol ogical and biochemical analyses demonstrated that P. citrea isolated f rom diseased pineapple fruit in the Philippines possesses features ide ntical to those of an American Type Culture Collection type strain of P. citrea and not to those of P. ananas, P. herbicola (formerly Erwini a herbicola), and P. stewartii (formerly Erwinia stewartii). P. citrea induces the production of compounds in pineapple which become pink to reddish-brown upon cooking the fruit, pulp, or juice. This distinct c olour is not induced by Escherichia coli, Agrobacterium tumefaciens, B urkholderia gladioli, Pseudomonas fluorescens, Gluconobacter oxydans, Acetobacter aceti, and Acinetobacter calcoaceticus. Like other well ch aracterized bacteria pathogens, such as Pseudomonas syringae pv. phase olicola, P. citrea elicits the hypersensitive response (HR) in tobacco . By contrast, G. oxydans and A. aceti that have been previously impli cated 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 locat ed on its chromosome. The pink colour can be restored in an avirulent, pink colour defective mutant strain, CMC6, by complementation in tran s with a specific 3.8 kb genomic DNA fragment of P. citrea. This sugge sts that P. citrea contains the genetic elements that are required for pink disease.