ENTEROBACTER-CLOACAE IS AN ENDOPHYTIC SYMBIONT OF CORN

The bacterium Enterobacter cloacae is presently used for biocontrol of postharvest diseases of fruits and vegetables and as a preplant seed treatment for suppression of damping-off. This bacterium has apparent affinities for several grass species, but it is not considered to be a n endophyte. While screening corn for fungi and bacteria with potentia l for biocontrol of various corn diseases, the surface-sterilized kern els of one unknown Italian corn cultivar produced fungus-free corn see dlings with roots endophytically infected by E. cloacae. This paper de scribes the microscopic nature off. cloacae RRC 101 with corn, and the in vitro control of Fusarium moniliforme and other fungi with this ba cterium. Light and electron microscopy determined that this isolate of E. cloacae was biologically associated with corn seedling roots, wher e it was distributed intercellularly within the cortex and stele. This is a first report of a strain of this bacterium as an endophytic symb iont of roots. Following a topical application of E. cloacae to kernel s, and upon germination this bacterium readily infected roots of two o ther corn cultivars. The bacterium was observed within the endosperm o f germinating corn seedling, but germination was not affected. Further , the bacterium was isolated from leaves and stems of 3- to 6-week-old seedlings indicating that the above ground portions of corn were also colonized. There was no evidence of damage to cells of the root durin g a three to four week observation period. This bacterium was antagoni stic to several isolates of the corn pathogen Fusarium moniliforme, an d to two other species of fungi, all of which produce mycotoxins on co rn.