Phenotypic and Genetic Characterization of Erwinia carotovora spp. carotovora (Jones) Bergey et al. Isolates from Grafted Tomato in Sardinia, Italy

Abstract

A disease symptomatically similar to that caused by Erwinia carotovora occurred on “Cuore di Bue” and “Cencara” tomato plants grafted on “Beaufort” and “He-Man”, or ungrafted, in greenhouses in Sardinia (Italy). Symptoms were: dark brown/black longitudinal stem lesions, soft stem rot, pith breakdown of the stems, hollow stems, vascular tissue discoloration, wilting and collapse of the plants. Numerous bacterial colonies from stem tissues were isolated on yeast extract salts (YS) medium. Seven isolates (DPP As-1, DPP As-2, DPP As-3, DPP As-14, DPP Pu6, DPP Pu7 e DPP Pu8) were selected on the basis of their ability to cause rot on potato pieces and a hypersensitivity reaction in “White burley” tobacco leaves. Pathogenicity tests revealed that five of these isolates infected artichoke, basil, dwarf bean, fennel, marrow, melon, pepper, eggplant, grafted and ungrafted tomato, and white cabbage. Of the remaining two isolates, one (DPP As-1) did not infect white cabbage, and the other (DPP Pu8) did not infect basil, marrow or white cabbage. Phenotypic properties and ELISA, also performed on naturally infected tissues, revealed that all the isolates were E. c. ssp. carotovora (Jones) Bergey et al. PCR-RFLP analysis placed two (DPP As-2 and DPP As-3) of the seven isolates in RFLP group 8. Five isolates belonged to a hitherto unknown RFLP group. Prevention and control measures for this disease are suggested.