Head Rot of Cauliflower Caused by Pseudomonas fluorescens in Southern Italy

Bacterial isolation from water soaked and brown discoloured and rotted cauliflower heads in commercial fields in Apulia, Southern Italy, resulted, in all the specimens, in almost pure cultures with the LOPAT profile (++−+−) of the group Vb of fluorescent pseudomonads. A fluorescent pseudomonad with the LOPAT profile (−+++−) of the group IVb was also obtained from only one out of ten samples examined. The latter isolate, on the contrary of the former ones, produced pectolytic enzymes since it was able to rot potato in the potato disk assay and utilize the pectin. The nutritional analysis of the above isolates with the computerised system Biolog led to the identification of the isolates belonging to first and second groups as strains of Pseudomonas fluorescens and Pseudomonas spp., respectively.

Pathogenicity assays performed by spraying detached cauliflower florets with 10⁸ cfu/ml bacterial suspensions showed that the above pseudomonads reproduced the floret brown discoloration and rotting observed in the field. A similar result was obtained when the florets were dipped in the above bacterial suspensions. Furthermore, the brown discoloration and rotting of internal tissues were obtained when the above suspensions were injected into the floret peduncle.