Serological detection of bacterial pathogens associated with rotted potato tubers

Studies were conducted in the Department of Plant Pathology, College of Agriculture, Orissa University of Agriculture and Technology, Odisha, India in 2010-2011 on serological detection methods for identification of bacterial pathogens associated with rotted potato tubers. One hundred and two rotten potato tubers of KufriJyoti variety were collected from freshly harvested lot of All India Co-ordinated Potato Improvement Project, Orissa University of Agriculture and Technology. Tubers were cut into two equal halves and categorized into 6 groups, on the basis of internal symptoms exhibited, that is, (A) cut tubers showing brownish discolouration along the vascular region, (B) cut tubers showing brownish discolouration along the vascular region with soft rotten cavities filled with whitish ooze, (C) cut tubers showing brownish blackish discolouration along the vascular region and soft rotten tissues extending towards centre, (D) cut tubers showing soft rotten tissues extending towards centre without brownish discolouration, (E) cut tubers showing soft rotten tissues extending towards centre with brownish black discolouration, (F) cut tubers showing dry tissues with cavities surrounded by soft tissues. The association of two bacterial species was assayed following tube agglutination test using the known antiserum for each bacterium, Ralstonia solanacearum and Pectobacterium carotovorum. It was revealed that R. solanacearum could be associated exclusively with 54.10% of diseased tubers with symptom Category–A. No other bacteria could be detected from the rest of the samples belonging to the said category. Similarly, exclusive association of P. carotovorum could be detected in 87.50% of the rotten tubers with symptom Category–D. In the symptom categories B, C, E and F, both test bacteria were found to be associated either singly or as mixture. Least bacterial infection due to P. carotovorum (12.5%) was observed in symptom Category–F. It is a very quick detection method which can reveal the percentage of bacterial pathogen association after two hours of testing.