PHENOTYPIC AND GENETIC CHARACTERIZATION OF ERWINIA CAROTOVORA SUBSP. CAROTOVORA STRAINS ISOLATED FROM GRAFTED TOMATO IN SARDINIA.

Recently a disease symptomatically similar to that induced by
Erwinia carotovora in tomato (Lycopersicon aesculentum Mill) has
been observed in some Sardinian greenhouses on cvs Cuore di
Bue and Cencara grafted onto Beaufort, He-Man, Camone, and
Cencara. Symptoms, which developed during ripening of the first
fruit, consisted of 10 to 15 cm long dark brown/black longitudinal
lesions of the stem, soft stem rot and dissolution of the pith,
vascular tissue discoloration, wilting and collapsing of the whole
plant. About 8% of the plants were infected in the damper
greenhouse areas. Numerous bacterial colonies were obtained on
YS from diseased internal stem tissues. Seven colonies were selected
based on their ability to induce rotting of potato slices and
a hypersensitive response in White burley tobacco leaves. For
pathogenicity tests, a drop of bacterial suspension was placed on
the primary leaf node of the stem of five four-week-old greenhouse
tomato plants. Five isolates could infect artichoke, basil,
bean, fennel, zucchini, melon, pepper, grafted and non-grafted
tomato, and white cabbage. One isolate could not infect white
cabbage and one basil, zucchini, and white cabbage. Pathogenicity
tests and morphological, biochemical and physiological characterisation
showed that the seven bacterial isolates belonged to Erwinia
carotovora subsp. carotovora. Identification was confirmed
by ELISA using the serum anti E. carotovora subsp. carotovora
CFBP 2046. Preliminary identification was also made by PCR using
Y1 and Y2 primers. Restriction fragment length polymorphism
(RFLP) analysis of the 434 bp PCR amplification product
placed two of the seven isolates in RFLP group 8, but five isolates
did not fit in any of the known RFLP groups. This seems to be
the first record of this disease on greenhouse tomatoes in Italy.