Biological control tobacco bacterial wilt and black shank and root colonization by bio-organic fertilizer containing bacterium Pseudomonas aeruginosa NXHG29

Tobacco bacterial wilt (TBW) and tobacco black shank (TBS) are two of the most devastating tobacco soil-borne diseases worldwide. In this study, Pseudomonas aeruginosa NXHG29 exhibited dually antagonistic activities against TBW and TBS in vitro assays. Pot experiments were performed to evaluate the capability of a novel bio-organic fertilizer (BOF) consisting of organic fertilizer with NXHG29 to control TBW and TBS. The results showed that application of BOF could more effectively decrease the disease incidence of TBW and TBS than the direct application of NXHG29. Higher amounts of BOF application (0.5% and 1% amendment) resulted in the more suppressive effects on tested pathogens when compared with a low amount of BOF application (0.1% amendment). To determine the antagonistic mechanism of NXHG29, we investigated the colonization pattern of NXHG29 on tobacco roots in a sand system and a natural soil system by tagging NXHG29 with a GFP-marked plasmid. Similar observations were obtained in the two systems. The results indicated that GFP-tagged NXHG29 colonized first the differentiation zones followed by the elongation and maturation zones of the primary roots and subsequently around the junctions of primary and lateral roots. The population dynamics of GFP-tagged NXHG29 on tobacco roots and in the rhizosphere were also monitored. The development of the BOF using dually antagonistic bacteria might provide new options for control strategies, especially with respect to managing both diseases simultaneously in the host plant, which should be more effective in the long term.