Soluble Concentrate Formulation of Oxalic Acid and N-Acetyl-L-Cysteine: Potential of Use in Controlling Ralstonia solanacearum

Abstract

Brown rot is a disease caused by the bacterium Ralstonia solanacearum and has the potential to cause significant losses due to tubers rotting of infected potato plants. The chemical control of R. solanacearum is ineffective and the biological control methods have not yet been developed against this organism. The antibacterial activities of a soluble concentrate (SL) formulations of oxalic acid (OXA), and N-Acetyl-L-cysteine (NAC) were tested against R. solanacearum race 3 biovar 2. Formulations of OXA SL 13%, NAC SL 10%, and OXA+NAC SL 23% showed inhibition zones against R. solanacearum. In the case of NAC SL 10%, and OXA+NAC SL 23%, the inhibition zone consisted of two regions, a clear inhibition zone, and a less clear inhibition zone. After 72 h. of incubation, the final total inhibition zone was 35.3, 33.3, and 60.0 mm for OXA SL 13%, NAC SL 10%, and OXA+NAC SL 23%, respectively. Both the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of OXA+NAC SL 23% against R. solanacearum were 62.5 μl/ml. Formulation of OXA+NAC SL 23% exhibited good stability at different storage conditions and no separation was observed during the stability test. In the pots experiment, the wilt index and the percentage of wilted plants were decreased significantly in OXA+NAC SL 23% treatments compared to the positive control (treated with R. solanacearum only) treatment. The number and weight of potato tubers were significantly increased using the concentrations 125 and 62.5 μl/ml of OXA+NAC SL 23% compared to the positive control. Field experiments are needed to confirm the results.