ROOT INDUCTION BY AGROBACTERIUM-RHIZOGENES IN WALNUT

Agrobacterium rhizogenes (wild-type, strain 1855), when applied to the basal part of microcuttings of walnut (J. regia L.), produced numerou s adventitious roots in vitro: 58.6% of rooting was induced in microcu ttings in hormone free medium and 62.9% and abundant callus formation in the presence of IBA. A, rhizogenes did not induce rooting when IAA was present in the rooting medium. No explants were induced to root by the treatments with IBA, IAA or in hormone free medium without the pr esence of A. rhizogenes. Root vascular elements were connected to the microcutting vascular system in the treatment with A. rhizogenes in HF M and were successfully transferred to soil: However, microcuttings tr eated with A. rhizogenes + IBA showed vascular connections not correct ly formed. Southern blots performed using the fragment containing rol genes, as probe, coming from pBIN19::Eco15, provided molecular evidenc e of the transgenic nature of the roots induced by A. rhizogenes.