AGROBACTERIUM-TUMEFACIENS AFTER IN-VIVO INOCULATION OF POTATO (SOLANUM-TUBEROSUM L) (SCANNING ELECTRON-MICROSCOPY)

Five weeks after the in vivo inoculation of potatoes (Solanum tuberosum L.) with Agrobacterium tumefaciens strain B6S3, bacteria were found in the non-differentiated cells of tumors (formed from xylem parenchyma or other living cells), in xylem cells at the site of inoculation, as well as in xylem cells of the adjacent stem. Bacteria were attached by fibrillar aggregates to the tumor cell walls. They were also attached to a fibrillar mass which arose from agrobacteria connected to this mass in the tumor. Agrobacteria, singly or in pairs, were attached to an electron dense formation (possibly bacterial extracellular polysaccharides) found both inside the xylem cells of the stem adjacent to the tumor and at the site of inoculation, Some A. tumefaciens cells were attached by means of a pedestal-like structure at the inoculation site. A possible function of the different means of attachment of A. tumefaciens in both non-transformed plant cells and tumors is discussed.