PCR-based sensitive detection of Ralstonia solanacearum from soil,eggplant, seeds and weeds

Ralstonia solanacearum is an economically important, bacterial plant pathogen which affects a wide range of crop plants. R. solanacearum survives in the soil for many years and weeds serve as symptomless carrier. One of the important aspects in controlling R. solanacearum is its early detection. In this study, detection threshold of R. solanacearum in the soil was standardised using polymerase chain reaction (PCR) method. The minimum threshold limit ranged between 6.8 × 10 and 3.6 × 10² CFU g^?1 of soil. Using this standardised protocol R. solanacearum was detected from the rhizosphere soil of eggplants showing varying degrees of wilt. PCR method was quite sensitive to detect R. solanacearum from the xylem fluid of eggplant. Presence of R. solanacearum in the soil infected with capsicum wilt was also demonstrated successfully and the minimum detection limit was 4 × 10² CFU g^?1 of soil. The bacterium was not detected from the eggplant seeds collected during 2006 and 2007 seasons. However, the bacterium was detected from the weed (Alternanthera sessilis) grown in the eggplant field indicating the possibility of weeds serving as symptomless carrier. Using our method, it is possible to detect R. solanacearum from soil, plant and weeds grown in the field at an early stage so that proper management strategies could be taken to prevent the infection and further spread of the pathogen.