Quantitative Analysis of the Migration and Accumulation of Bacillus subtilis in Asparagus officinalis

Bacillus subtilis B96-II is a broad-spectrum biological control strain. It effectively suppresses soil-borne fungal diseases in vegetables. A green fluorescence protein (GFP) was expressed in B96-II to detect migration of B96-II into the root and stem of asparagus. The GFP-tagged B96-II (B96-II-GFP) strain exhibited bright green fluorescence under a fluorescence microscope. GFP was stable and had no apparent effects on the growth of the strain. Asparagus plants were planted in the soil inoculated with B96-II-GFP. Our results showed that B96-II-GFP was detected in both the root and stem 15, 30, and 45 days after the asparagus seedlings were planted. B96-II-GFP was also detected in leaves but at a lower concentration. The highest concentration was detected in 15 days, and the number of bacteria decreased subsequently irrespective of duration of growth or sampling period. The highest concentration of B96-II-GFP was present in the root base suggesting that the root base served as the hub of bacterial migration from the soil to the stem.