COMPARISON OF STRAINS OF AGROBACTERIUM-VITIS FROM GRAPEVINE SOURCE AREAS IN AUSTRALIA

Dormant cuttings from grapevine source areas in three Australian state s were indexed for the presence of Agrobacterium vitis, the causal age nt of crown gall disease of grapevine. The bacterium was present at va rying levels in both rootstock and scion material from New South Wales , Victoria, and Western Australia. A genomic DNA fingerprinting techni que was used to compare these strains of A. vitis with strains previou sly isolated from South Australian propagation material and with strai ns from the United States of America, particularly strains from the Un iversity of California at Davis where a number of Australian grape cul tivars originated. Nine distinct DNA fingerprint types were found, dem onstrating that A. vitis is a genetically heterogeneous species. There were no DNA fingerprint types in common between Australian states, su ggesting that little or no transfer of A, vitis between states has occ urred. Two Californian strains were indistinguishable, when analysed b y DNA fingerprinting, from strains isolated over a 14 year period in S outh Australia. This finding is strong circumstantial evidence that A. vitis was introduced to South Australia on grapevine cuttings importe d from California. Given the fact that A. vitis is probably not indige nous to Australia, it is possible that the different strains found in each state were the result of independent introductions. Although grap evines from all Australian states tested did contain A. vitis, the exi stence of unique strains in each state means that the restrictions on movement of grapevine material between states should be maintained, an d that quarantine authorities should avoid introducing further strains of the bacterium.