Towards effective biocontrol of Phytophthora root rot in annual crops: A meta-analysis

Phytophthora comprise the most destructive plant pathogens, affecting over 1,000 plant species and causing severe diseases such as root rot. Traditional chemical control methods may pose environmental risks and can contribute to resistance development, making alternative strategies such as the implementation of biological control organisms (BCOs) essential. This study presents a meta-analysis evaluating factors that influence the success of BCOs against Phytophthora root rot in annual crops. Systematic data collection and statistical analyses of 49 studies comprising 355 BCO treatments resulted in key insights into the most effective BCO application methods. Root and soil treatments were significantly more effective than seed treatments. Co-application of BCOs with pathogen inoculation enhanced efficacy, likely due to direct antagonism, particularly when specialized metabolites were delivered alongside bacterial BCOs. Strikingly, greenhouse and field trials demonstrated higher BCO efficacy than growth chamber experiments, emphasizing the importance of trial environments. Factor Analysis of Mixed Data (FAMD) and Hierarchical Clustering on Principal Components (HCPC) identified distinct clusters of BCO treatments, revealing clear associations between BCO application methods and efficacy. These findings highlight the need for optimized application methods and formulations to maximize BCO stability and efficacy, potentially enhancing their role in integrated pest management strategies.