In an attempt to improve rooting in in vitro propagated Eucalyptus clones, root-inducing genes on the Ri plasmids of three Agrobacterium rhizogenes strains were inserted into the Eucalyptus genome. Root development was monitored in vitro and after the plantlets had hardened off. Only transformed roots grew as root cultures in hormone-free liquid medium. The potential use of this procedure for improving rooting of clonal material is discussed.

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For a bacterium to be a successful biocontrol agent against crown gall disease, it must produce an effective agrocin specific for Agrobacterium tumefaciens and be able to colonize host plants efficiently. The colonization abilities of K84 and J73, successful and potential biocontrolling strains, respectively, were compared both in vivo and in vitro. Both strains produced fibrils attaching them to tomato root surfaces and had similar colonization efficiencies up to 14 days after inoculation. However, the ability of J73 to colonize plants for longer periods was significantly less than that of K84. Thus, the presence of fibrils is not sufficient to ensure colonization. No correlation was found between hydrophobicity and colonization.