Effect of Hot Water Treatment on Systemic Agrobacterium tumefaciens Biovar 3 in Dormant Grape Cuttings

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Abstract
Agrobacterium tumefaciens biovar 3 (AT3) was eradicated or reduced to below the level of detectionin dormant cuttings of grape rootstocks K5140 (Vitis champinii .times. V. riparia) and Ramsey (V. champinii) and in artificially infested Cayuga White (interspecific hybrid) by a hot water treatment (exposure to 50 C for 30 min). Strains of AT3 varied in their sensitivity to heat, but were generally more sensitive than strains of biovar 1 or biovar 2. Populations of about 103 colony-forming units per milliliter of AT3 in broth were killed by a 30-min treatment. Biovar 1 strains were apparently unaffected by 50 C, even when exposed for 30 min. Nontumorigenic biovar 1 strains were recovered from hot water treated cuttings. The hot water treatment may offer a simple, effective, economical, and environmentally safe means of eradicating AT3 from dormant cuttings.