Hot Water Treatment of Dormant Grape Cuttings Reduces Crown Gall Incidence in a Field Nursery

Abstract

Hot water treatment (50°C, 30 min) reduced the level of Agrobacterium tumefaciens biovar 3 below detection in naturally infested grape scions (cvs. Chardonnay and Zante Currant) and rootstocks (cvs. Ramsey and K51-40). Material was bench-grafted, then planted in a field nursery. After one season's growth, less than 2% of the hot-water-treated, grafted vines showed crown gall symptoms. In contrast, up to 60% of untreated control vines were galled. Hot water treatment had variable effects on graft take, dependent on cultivar, but there were no negative effects on vine growth or mortality in the nursery. After vines were grown in the nursery, A. tumefaciens biovar 3 was detected systemically in up to 16% of heat-treated vines for some scion/rootstock combinations while up to 60% infection was observed in control vines. Hot water treatment provided good control of crown gall symptoms but may have to be modified for use where complete eradication of the pathogen is required.