Screening and identification of an antagonistic bacterium XF10 against tobacco black shank

In order to quickly and effectively screen out antibacterial strains that have obvious antagonism against tobacco black shank, 300 soil samples were collected from the healthy plants' rhizosphere in serious tobacco black shank incidence areas. A strain, XF10, was obtained by rapid initial screening of pathogenic bacteria and confrontation culture. The appearance of XF10 colony was round with a smooth surface and neat edges. XF10 could produce orange pigment and was identified by morphological characteristics, biological phenotype identification, BIOLOG automatic microbiological identification system and 16S rDNA sequence analysis. The results showed that the homology of sequence between XF10 and several Pseudomonas chlororaphis strains in Pseudomonas reached 99%, therefore XF10 was identified as Pseudomonas chlororaphis. Both bacterial fluid and extracellular metabolite crude extract of XF10 possessed more than 80% inhibitory rate on Phytophthora parasitica var. nicotianae (Breda de Haan) Tucker. Moreover, the volatile metabolites of XF10 could inhibit the growth of pathogenic hyphae with an inhibition rate of 86%.