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Evaluation of small molecules of biofilm-inhibiting compounds for control of bacterial spot of tomato

Qingchun Liu: UF-TREC

<div>Bacterial spot, primarily caused by <em>Xanthomonas perforans</em>, is a challenge to tomato production of Florida. Infection of tomato seedlings may result in total crop loss, and infection of enlarging fruit can make them unmarketable. However, effective strategies for growers to control this disease are very limited. Exploring alternative approaches for effectively managing this important disease for the tomato industry is imperative. Small molecules of biofilm formation-inhibiting compounds have been extensively studied for improved control of bacterial pathogens in medical research, but little has been done with regards to plant pathogens. In our greenhouse study, three small molecules, i.e. N-acetyl-L-cysteine (NAC), 3-indoleacetonitrile (IAN) and D-leucine, were found effective in significantly (<em>P</em><0.05) reducing bacterial spot of tomato. NAC at 10 mg/mL, IAN at 1 mg/mL and D-leucine at 10 mM significantly reduced disease severity by 55%, 91% and 27%, respectively, compared to the non-treated control. When IAN was applied 3 and 1 day before, the same day, 1 and 3 days after pathogen inoculation, disease severity was reduced by -6.7%, 34%, 91%, 90%, and 38%, respectively. These results indicate that small molecules of biofilm formation-inhibiting compounds are effective against bacterial spot of tomato and could be incorporated into integrated pest management programs for control of this economically important disease in tomato production.</div>