Effect of Shoot Age and Tip Culture Propagation of Grapes on Systemic Infestations by Agrobacterium tumefaciens Biovar 3

Abstract

Agrobacterium tumefaciens biovar 3 (AT3), the cause of grape crown gall, was detected systemically in grape shoots that were collected in late August and October but not in green shoots collected in May, July, or early August. The pathogen did not migrate short distances from inoculation points on canes into green shoots within one month in greenhouse experiments. Vines produced by shoot tip culture were free of AT3 regardless of whether the original tips were taken from shoots of known AT3-infested or apparently clean plants. Vines propagated by shoot tip culture remained free of the pathogen when grown on tissue culture media or in a potting mixture in the greenhouse for six months.