Effects on Tomato Bacterial Canker of Resistance Inducers and Copper Compounds in Greenhouse.

Bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis produces considerable economic losses in many countries because effective control measures are lacking. In this study, the effectiveness of some chemicals, a plant growth regulator (Prohexadione-Ca (PC)), two plant activators (hydrogen peroxide (HP)) and harpin protein (Hrp), fungicides, maneb+copper (MC), copper compounds (copper sulfate pentahydrate (CSP) copper hydroxide (CH) and copper oxychloride (CO)) and an antibiotic, streptomycin sulphate on the pathogen were assessed in vitro and in vivo on two tomato cultivars, Newton and Orient. In Hrp and HP treated plants, reduction in disease severity (about 45%) was correlated with suppression of bacterial growth during the time course of infection. The activities of POX, GPX and PAL enzymes were determined at 5th day as markers of resistance and applications of Hrp, PC and HP induced a progressive and significant increase of both enzymes in locally treated tissues. Only PC treatments have decreased plant heights and the effectiveness of PC in reduction of plant heigths was up to 40%. Among copper compounds, CSP and CO combination with Maneb were the most effective on the disease severity (about 50%). In addition, CSP combination with Hrp, HP and PC significantly limited the pathogen population in vitro and they showed considerable effects on the disease symptoms compared with CSP alone. We conclude that Hrp, HP and PC may be useful in controlling external symptoms of this disease in greenhouses, and is environmentally friendly, reducing the amount of copper applied to crops. [ABSTRACT FROM AUTHOR]