Abstract: Grape crown gall disease is a soil-borne bacterial disease caused by virulent strain of A.vitis. Biocontrol bacteria has been one of the efficient methods to control the disease. Evaluation of biocontrol effect is extremely important in screening of potential biocontrol agent. At present, the effect testing is performed by inoculating indicator plant or host plant in vivo. In this communication, we investigated the effect of E26 through inoculating grape stem and leaf in vitro. 1/2B5 medium was modified for better growth of grape stem in vitro culture, and the best methods of sterilization and inoculation were screened in this experiment. The stem in vitro test demonstrated the same effect when compared with the in vivo test, and could be the quick and accurate evaluation to indicate the effect of E26. While the grape leaf in vitro test could not accurately reflect the effect of E26, because crown galls formed only on leaf veins and were too small to be examined. The grape stem in vitro testing can be a promising method to detect the effect of E26.

Key words: grape crown gall, Biocontrol effect, testing In vitro