PREVALANCE OF BROWN ROT OF POTATO IN SOME SELECTED LOCATION OF BANGLADESH AND IN-VITRO MANAGEMENT OF RALSTONIA SOLANACEARUM

Abstract

An experiment was conducted in the Disease Diagnostic Laboratory of Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka during the period of 2014- 2015 to observe the prevalence of brown rot disease in stored potato tuber collected from different locations of Bangladesh and to find out suitable antibacterial chemicals and antagonists against Ralstonia solanacearum, the causal organism of brown rot of potato. Potato samples were collected from eight potato growing region viz. Munshigong, Rangpur, Lalmonirhat, Joypurhat, Pabna, Bogra, Manikgonj and Panchagarh. The highest disease incidence (40 %) was observed in potato tuber collected from Munshigong at six month storage period and the lowest incidence (3.33%) was found in potato tuber collected from Panchagarh at two month storage period. Disease incidence varied significantly from location to location and storage period. The causal organism of brown rot of potato was identified as Ralstonia solanacearum on the basis of morphological, biochemical and cultural characteristics. The bacterium was gram negative, rod shaped and showed positive results in KOH solubility test, catalase test, starch hydrolysis test, levan production test, pecteolytic test, gelatin liquefaction test and negative result on oxidase test. It produced highly fluidal, slightly raised and creamy white colonies with light pink or pinkish red centre and irregular margin after 48 hrs of incubation at 30 0C on TTC medium. Four agrochemicals viz. Kasumin, Bactrol, Copperoxichloride and copper+mancozeb and two bioagents such as Bacillus subtilis based formulation (PRH) and Trichoderma harzianum were tested against Ralstonia solanacearum in the laboratory. Among them the highest inhibition zone (14.44 mm) was recorded when Kasumin used against Ralstonia solanacearum wheres Bactrol, Bacillus subtilis, Trichoderma harzianum and Copperoxychloride showed moderate inhibition zone. However, copper+mancozeb did not show any effect against Ralstonia solanacearum.