Efficacy of a biological control agent Rhizobium vitis ARK-1 against Virginia R. Vitis isolates, and relative relationship among Japanese and Virginia R. vitis isolates

Non-tumorigenic Rhizobium (syn. Agrobacterium) vitis strain ARK-1 (ARK-1) has been shown to reduce crown gall in grapevine (Vitis vinifera) seedlings when co-inoculated with Japanese tumorigenic isolates of R. vitis. The objectives of this study were to test ARK-1's efficacy as a biological control agent against R. vitis isolated from grapevines in Virginia, and to examine genetic diversity of R. vitis found in Virginia, USA and Japan. ARK-1 was co-inoculated into wine grape trunks (V. vinifera cv. 'Cabernet Sauvignon') with a tumorigenic R. vitis isolate at a 1:1 cell ratio (similar to 10(8) cell/ml). A total of four R. vitis isolates were tested individually. Compared to treatments of a tumorigenic isolate alone, ARK-1 co-inoculation significantly decreased (P <= 0.05) the mean probability of gall formation in all cases, and the mean gall diameter in all, but one case (isolate ACME15). The average reduction was 90% and 92% in the mean probability of gall formation and mean gall diameter, respectively. We conducted exploratory data visualization with distance-based clustering and correspondence analysis using data from ISSR-and rep-PCR, which showed separation of Virginia and Japanese isolates and placement of ARK-1 near to Virginia isolates. These results suggest that ARK-1 is a good candidate for biocontrol of grapevine crown gall in the mid-Atlantic region of the USA.

Automated summary

Non-tumorigenic Rhizobium (syn. Agrobacterium) vitis strain ARK-1 has been shown to effectively reduce crown gall formation in grapevines when co-inoculated with tumorigenic R. vitis from Japan. The study tested ARK-1's efficacy against R. vitis isolates from Virginia, USA and Japan, showing promising results for biocontrol of grapevine crown gall in the mid-Atlantic region of the USA. Genetically, ARK-1 was found to be closely related to Virginia isolates, indicating its potential as a biological control agent.