Biological Control for Grapevine Crown Gall Evaluated by a Network Meta-Analysis

Grapevine crown gall (GCG), which is caused by Allorhizobium vitis (=Rhizobium vitis) tumorigenic strains, is the most important disease of grapevine around the world. Previously, nonpathogenic A. vitis strains VAR03-1, ARK-1, ARK-2, and ARK-3 were identified as promising biological control agents, but the control effects of each strain were not directly compared and assessed in the field because field trials were conducted in different fields and years. Thus, the results of the control effects obtained from 16 field trials in 12 years from 2006 to 2017 were analyzed and evaluated by a linear mixed model (LMM) and a network meta-analysis (NMA). The results of the LMM strongly indicate that the factor antagonistic strain was significantly related to the biological control activity in this study, but the other factors, concentration of cell suspension, field, and year, were not. Then, the results of 16 field trials were combined in an NMA. The estimated relative risk (RR) after treatment with ARK-1, ARK-2, ARK-3, VAR03-1, and K84 were 0.16, 0.20, 0.22, 0.24, and 0.74, respectively. In conclusion, strain ARK-1 was the best antagonist regardless of the concentration of the cell suspension, field, and year differences, and it can be recommended to control GCG.

Automated summary

Grapevine crown gall, caused by Allorhizobium vitis, is a significant disease worldwide. Four nonpathogenic A. vitis strains, VAR03-1, ARK-1, ARK-2, and ARK-3, have shown promise as biological control agents, but their control effects have not been directly compared. This study analyzed 16 field trials conducted between 2006 and 2017 to evaluate the control effects using a linear mixed model and network meta-analysis. The results suggest that the strain ARK-1 was the most effective antagonist against grapevine crown gall.