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

Area of Science:

• Plant Pathology
• Microbiology
• Agricultural Science

Background:

• Grapevine crown gall (GCG), caused by tumorigenic *Allorhizobium vitis*, is a globally significant grapevine disease.
• Nonpathogenic *A. vitis* strains (VAR03-1, ARK-1, ARK-2, ARK-3) show potential for biological control.
• Previous field assessments lacked direct comparative data due to varied trial conditions.

Purpose of the Study:

• To comprehensively evaluate and compare the efficacy of nonpathogenic *A. vitis* strains for biological control of GCG.
• To identify the most effective strain for GCG management under diverse field conditions.

Main Methods:

• Analysis of 16 field trials conducted over 12 years (2006-2017).
• Application of a linear mixed model (LMM) to assess factors influencing biological control activity.
• Utilized network meta-analysis (NMA) to combine results and estimate relative risks (RR) for different strains.

Main Results:

• The LMM confirmed 'antagonistic strain' as a significant factor, while 'cell suspension concentration', 'field', and 'year' were not significant.
• NMA revealed strain ARK-1 had the lowest estimated relative risk (RR=0.16), indicating superior GCG control.
• Other strains showed varying efficacy: ARK-2 (RR=0.20), ARK-3 (RR=0.22), VAR03-1 (RR=0.24), and K84 (RR=0.74).

Conclusions:

• Strain ARK-1 is the most effective biological control agent for grapevine crown gall, irrespective of environmental variables.
• ARK-1 can be reliably recommended for GCG management in vineyards.
• This study provides robust, comparative data supporting the use of specific *A. vitis* strains in integrated pest management strategies.