Effect of Sodium and Ammonium Bicarbonate in Managing Soft Rot Pathogen (Erwiaia carotovora ) of Carrot (Daucus carota )

Abstract

Soft rot in carrot (Daucus carota) caused by Erwinia carotovora is one of the most serious and economically important postharvest diseases in Sri Lanka which causes severe loss especially during storage and transit. Hence, this study was conducted with the objective of determining an effective control method for soft rot in carrot using two Generally Recommended As Safe (GRAS) chemicals namely, sodium bicarbonate and ammonium bicarbonate. In this study, the effect of those chemicals at different concentrations was evaluated on bacterial growth in vitro and the most effective chemical was selected based on reduction of colony count. Effectiveness of the selected chemical was investigated on inoculated and naturally infected carrots and untreated, un-inoculated carrots were considered as controls. Changes of the physico-chemical and organoleptic properties of the treated carrots were evaluated during the storage up to nine days at 28 QC±2 and 65-70% RH. Each treatment was triplicated and the experiments were repeated four times. Efficacy of ammonium bicarbonate at 2 % (w/v) on inhibition of bacterial growth was highly significant (p<0.0001) both in vitro and in vivo. Non-treated control carrots diseased completely after nine days where it was reduced by 75% with 2% ammonium bicarbonate on naturally infected carrots. Carrots that were inoculated before the treatment of 2% ammonium bicarbonate gave 50% disease reduction after nine days of storage. Sensory attributes and the physicochemical properties of the treated tubers did not change significantly during storage indicating the marketability of the treated tubers.