Identification and characterization of a <i>Bacillus subtilis</i> strain TS06 as bio-control agent of strawberry replant disease (<i>Fusarium</i> and <i>Verticilium wilts</i>)

Abstract

Replant disease is a major limitation for strawberry production in greenhouse. Bio-control may be a good way to cope with the replant diseases. Here, we report identification and characterization of a bacterial strain TS06 that may be used as a bio-control agent against the replant diseases in strawberry. TS06 was identified as a new strain of Bacillus subtilis based on the homology of its 16S rRNA and gyrA sequences to the reference strains in Genbank. It has a 7 bp difference from the most homologous strain B. subtilis NRRL B-23978. TS06 formed a monophyletic group with species of the B. subtilis complex group in the 16S rDNA sequence analysis, and shared similarity values of 99.9% with the B. subtilis type strains in the sequence analysis of the gyrA genes. TS06 was demonstrated to be a potent inhibitor to Fusarium oxysporum and Verticillium dahliae. There were 89.6 and 84.5% growth inhibition of TS06 on F. oxysporum and V.dahliae respectively in the antagonism test of TS06 strain in vitro. The mycelia growth inhibition rate of TS06 for F. oxysporum and V.dahliae reached 65.96 and 68.45% respectively, in the 40% TS06 culture filtrate treatments. Strain TS06 reduced the average percentage of strawberry diseases (Fusarium and Verticillium Wilts) by 88.94 and 79.94% respectively in greenhouse. In summary, B. subtilis strain TS06 has a broad antifungal spectrum and synchronously bio-control the two severe replant diseases (Fusarium and Verticilium Wilts), and TS06 can be developed as a biocontrol agent to be applied in strawberry production.

Key words: Bacillus subtilis, strain TS06, biological control, strawberry Fusarium wilt, strawberry Verticillium wilt.