A novel Pseudomonas fluorescens strain as a versatile measure against different bacterial plant diseases

In this study, the efficacy of the strain BB20 of P. fluorescens (Pf) bv.1 (Patent No. PCT/IB2012/050694; European Application No./Patent No. 12706932.6 – 1401) was in vitro and in vivo evaluated against several bacterial pathogens, agents of disease of different plant species. Moreover, preliminary solid and liquid formulations of the antagonist were firstly assayed for their time stability when stored at 4 °C and assayed against bacterial pathogens in in vivo experiments. In in vitro experiments BB20 inhibited the growth of several bacterial pathogen species by producing a peptidic antibacterial compound. Moreover, the antagonist suspension was able to prevent infections of Erwinia amylovora (Ea), Xanthomonas vesicatoria (Xv) and X. arboricola pv. pruni (Xap) by providing a relative protection of 62%, 64% and 58% when applied on pear, tomato and peach plants, respectively, under greenhouse and outdoor conditions. The solid and liquid formulations resulted stable and maintained the initial concentration for 6monthsat4°C. The in vivo efficacy of both solid and liquid formulations was comparable to that of fresh bacterial suspensions and resulted able to significantly reduce the fire blight incidence on pear plantlets and to statistically decrease the bacterial leaf spot severity on tomato plants and peach one-year-scions. The in vitro efficacy against a broad spectrum of bacterial pathogen species and the ability to prevent bacterial plant infections under controlled and field conditions pose the strain BB20 as a versatile tool in the frame of integrated control measures.