|Distribution of endophytic bacteria-Bacillus amyloliquefaciens SPX1 in tomato tissues and its potential on control of tomato bacterial wilt|
H. R. PAN (1), Y. J. Chen (2), W. H. Chung (1). (1) National Chung Hsing University, Taichung, Taiwan; (2) Kaohsiung District Agricultural Research and Extension Station, Pingtung, Taiwan
Previous studies indicated that endophytic bacteria (EB) could protect host plants from pathogenic infection. The EB of <i>Bacillus amyloliquefacines</i> SPX1 was able to inhibit the <i>Ralstonia solanacearum</i> and control the bacterial wilt (BW) of sweet potato. The objectives of this study are to analyze the distribution of SPX1 in tomato tissue and evaluate its efficacy on control of tomato BW. The inoculation tests indicated that SPX1 could spread in tissues of various hosts, including sweet potato, cucumber, tomato, etc. Further experiments revealed that SPX1 remained detectable in the whole stem of tomato 28 DAI. Thus, the movement of SPX1 strain proved to be systemically distributed in tomato. SPX1 maintained at a higher population (6.0 × 10<sup>4</sup> cfu/g tissue) in hypocotyls than in stems based on dipping method with hypocotyl-cutting seedlings. In addition, results from using the transformed strain, SPX1/DH5α (pAD43-25), with green fluorescent protein marker as inoculum demonstrated that the SPX1 could enter intercellular spaces and colonize xylems of tomato. Seven days after inoculation, SPX1 was detected from vascular bundles, cortex, epidermis and secondary roots. As for disease control, SPX1 was shown to reduce the disease severity of BW by 95.0% to 62.5% in tomato that had grown in the SPX1-infested soil (10<sup>6</sup> cfu/g soil) for 28days. Thus, the <i>B. amyloliquefaciens</i> SPX1 strain could potentially be used as a bio-agent on controlling BW of tomato.