Bacillus amyloliquefaciens subsp. plantarum active against quarantine bacteria causing serious epidemics in North-Central Italy

In Italy, in the last decades, the continuous spread of bacterial diseases in crops of considerable economic importance, the concomitant climate change and the need of a more environmentally sustainable agriculture have highlighted an increasing attention towards biological control measures integrated with appropriate agronomic techniques and preventive treatments which rely almost exclusively on the use of copper compound sprays on the plant surfaces. Since 2010 and in the following 10 years, we have tested Bacillus amyloliquefaciens subsp. plantarum (strain D747) to evaluate its efficacy to control some of the most important plant pathogenic quarantine bacteria that caused severe epidemics in North-Central Italy. In particular, the following pathosystems have been studied: Pseudomonas syringae pv. actinidiae (Psa) – Actinidia spp., Erwinia amylovora (Ea, from December 2019, RNQP pursuant to Regulation (EU) 2016/2031) – Pyrus communis, Xanthomonas arboricola pv. pruni (Xap) - Prunus persica, Xanthomonas vesicatoria (Xv) – Solanum lycopersicum. The biocontrol efficacy was tested in vitro and in planta, under greenhouse and field conditions, to test both direct or indirect effects. The strain D747 was highly effective in vitro against all four pathogens, it was able to survive on the different hosts and to reduce the pathogen populations and their disease severity. The biocontrol performance of the strain D747 was higher or comparable to the antagonistic strain QST713 of Bacillus subtilis, to chemicals as acibenzolar-S-methyl and to copper based compounds in greenhouse and field experiments. Moreover, the strain D747 was able to induce resistance responses against infection of Psa and Xv in their host plants.