Comparative Studies of Boxwood Endophytic Bacterial Isolates for Blight Control

Biological control presents a highly promising management strategy for boxwood blight. Recent investigations have led to the isolation of a diverse array of potent antagonistic endophytes from boxwood leaves. While some of these isolates have been individually evaluated, the assessment of others remained ongoing. The objective of this study was to compare their performance under standardized conditions to facilitate the selection of a prioritized subset for future research or development. Specifically, 15 bacterial endophytic isolates were evaluated against Calonectria pseudonaviculata (Cps) using dual culture assays. The six most effective isolates were further compared using in-planta experiments with container-grown B. sempervirens 'Justin Brouwers'. Overall, Bacillus subtilis 19FCG3-4 and Burkholderia sp. SSG consistently demonstrated superior performance compared to all other isolates in both dual culture assays and in-planta experiments. The selection and potential application of these leading candidates are discussed, alongside observed discrepancies in the screening experiments for biological control agents.