Endophytic bacteria as biological agents to control fusarium wilt disease and promote tomato plant growth

Plant endophytic bacteria are symbiotic bacteria that live in plant tissues and may play a role in disease control and/or plant growth promotion. In this study, six plant endophytic bacterial isolates, Arthrobacter sp. AM08, Pseudomonas aeruginosa AJ14, P. mosselii AB06, Bacillus cereus AP12, B. thuringiensis AK08 and Serratia marcescens AS09, were tested for their ability to control Fusarium oxysporum f. sp. lycopersici (FOL) and to promote the growth of tomato plant. The isolates were evaluated for their ability to produce hydrolytic enzymes (cellulase, protease and chitinase), hydrogen cyanide (HCN), indole 3-acetic acid (IAA), 1-aminocyclopropane 1-carboxylic acid (ACC) deaminase, and siderophores. The activity of cellulase, protease and chitinase enzymes was detected in all the isolates studied, whereas the highest HCN activity was observed in P. aeruginosa. The activity of IAA, ACC deaminase, and siderophore was also observed in all isolates, with B. cereus, P. mosselii, and S. marcescens being the highest producers of IAA and B. thuringiensis being the highest producer of siderophores. All isolates produced ACC deaminase at almost the same level. Application of the isolates to tomato seeds prolonged FOL incubation time, reduced disease incidence, and shortened xylem discoloration length compared to the controls, confirming the ability of the isolates to control FOL. In addition, all tested isolated showed plant growth pro-moting activity, as indicated by increased plant height and root length. The study showed that the endophytic bacteria are capable of controlling FOL and promoting the growth of tomato plant, revealing their potential to be developed as biocontrol agents.