Potential of Bacillus amyloliquefaciens strain d747 as control agent against Pseudomonas syringae pv. actinidiae

The strain D747 of Bacillus amyloliquefaciens (Amylo-X®) was assayed to evaluate its efficacy against Pseudomonas syringae pv. actinidiae (Psa), the causal agent of the bacterial canker of kiwifruit which assumed significant relevance after the heavy epidemics that have been occurring in central-northern Italy since 2008. The ability of strain D747 to inhibit the growth of two different Psa strains in vitro, its ability to survive and reduce populations of a rifampicin resistant pathogenic strain (CRA-FRU 3.1 Rifr) on female flowers of Actinidia chinensis, and its population dynamic on leaves of A. deliciosa were investigated. The microbial control agent was effective against Psa in vitro, and was able to survive on kiwifruit female flowers, reaching a population of approx. 106 CFU/flower 96 hours after its application. Moreover, it reduced the Psa population on A. chinensis flowers by more than one order of magnitude 48 hours after pathogen application. Furthermore, strain D747 of B. amyloliquefaciens survived on kiwifruit leaves for 14 days reaching a population of approx. 106 CFU/ml. These results suggest that strain D747 might be a promising tool for biological control of bacterial canker of kiwifruit.