Association of Pectolytic Fluorescent PSeudomonas with Postharvest Rots of Onion

H.H. El-Hendawy


Five isolates of pectolytic fluorescent pseudomonads were obtained from a rotted onion bulb and identified
as Pseudomonas marginalis. At both 4 and 25oC, all isolates caused soft rot to detached plant parts of onion and
to carrot, celery, cucumber, pepper, spinach, tomato and turnip (but not garlic). They did not however cause any
symptoms in living plants of these same species. These results suggest that the onion isolates are a postharvest
pathogen which is not destructive in the field but becomes a threat to fresh vegetables stored at low-temperature.
Analysis of cellulosolytic and pectic enzymes revealed that pectic lyases, but not polygalacturonases, pectin methyl
esterases and cellulases were produced in culture by each isolate.

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