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First Report of Burkholderia cepacia as a Pathogen of Banana Finger-Tip Rot in Taiwan

Banana finger-tip rot is an endemic minor disease in Taiwan. Diseased fingers are recognized externally by their distorted shape, often being narrow at the tip, smaller, and curved out of line with the other fingers. Parts of the pulp within the finger appear slightly gelatinous and yellow. Frequently, a brown discoloration is evident at the tip of the flower end. Although Pseudomonas sp. was reported to be a causal pathogen, the identity of the species was not determined (1). Isolations from diseased fingers consistently yielded bacterial colonies that were whitish-yellow on Luria-Bertani agar and did not produce fluorescent pigment on King's medium B. Three isolates were selected for further characterization. All isolates were gram negative, aerobic, and grew at 42°C, positive for oxidase, lysine decarboxylase, and ornithine decarboxylase, but negative for arginine dihydrolase and tryptophanase (indole production). The isolates hydrolyzed gelatin and esculin, produced acids by utilizing d (+)-glucose, mannose, sucrose, maltose, d-mannitol, d-sorbitol, and dulcitol, but not melibiose, or rhamnose. The isolates caused rotting symptom on onion that was more severe than on potato and carrot slices. The bacterium was identified as Burkholderia cepacia. Almost complete 16S rDNA sequence (1,489 bp; GenBank Accession No. AY207313) of one isolate (strain B9) was determined and compared with available 16S rDNA sequences of members of B. cepacia complex. The sequence was similar (99.87%) to that of B. cepacia genomovar III LMG 12614 (GenBank Accession No. AF097532). Bacterial suspensions (10⁸ CFU/ml) were injected through the center of the stigma, and the fingers were enclosed in a plastic bag to maintain high humidity. Twenty fingers (three to four fingers in each hand) were inoculated totally. A majority (80%) of the wound inoculations were successful, and typical symptoms appeared in 10 to 14 days. Control plants were inoculated with sterile distilled water. A small amount (2 to 5%) of control plants also showed symptoms. This may result from finger infestation with epiphytic or endophytic B. cepacia. Young fruits were more susceptible than older fruits. The bacterium was readily reisolated from diseased fingers and confirmed as B. cepacia. To our knowledge, this is the first report of B. cepacia as a causal pathogen of banana finger-tip rot.

Reference: (1) I. W. Buddenhagen. Plant Prot. Bull. 16:17, 1968.