DETECTION OF Clavibacter michiganensis subsp. sepedonicus, THE CAUSE OF BACTERIAL RING ROT OF POTATOES, IN JAWA BARAT AND EXPLORATION OF THE ANTAGONISTIC BACTERIA

• Main Author: Djaya, Luciana
• Format: Theses
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/36008
• Institution: Institut Teknologi Bandung

Clavibacter michiganensis subsp. sepedonicus (Cms), the causal organism of bacterial ring rot disease of potatoes, is a quarantine plant pathogenic bacteria. Its entry to and spread within Indonesia is strictly prohibited. The disease spreads through infected tuber. Indonesia used to import seed potato from several European countries where the disease had spread. It is suspected that the pathogen has infected potato grown in Pangalengan, Lembang, and Garut (Jawa Barat), the main potato producing areas in Indonesia. Once the bacteria is detected in Jawa Barat, anticipation in the control methods have to be prepared. Antagonistic microbes are widely used to control plant pathogens as the negative impacts are lower than synthetic pesticides. This biological control method is one of the components in Integrated Pest Management. Bacteria antagonistic to Cms were explored in the potato plant rhizosphere during the detection of the disease in potato field was carried out. Potato tubers from plants with disease symptom in the field and rejected tubers in the storage were collected. The tubers were cut and the disease symptom on the vascular ring was observed. The bacteria were isolated from the diseased tubers on NCP-88 and nutrient agar. After purification, they were Gram stained. Gram positive isolates were then tested serologically with ELISA kit (Agdia), so were the sap of potato tubers with symptom. Samples of 465 potato tubers were taken from the field and storage, 151 (32.5%) showed ring rot symptom. Bacteria were isolated from the tubers with disease symptom. Totally it was obtained 337 bacterial isolates, and 128 isolates were Gram positive. Result of the ELISA showed 28 isolates (8.3%) and 6 potato tuber saps were positive. This result suggested the detection of Cms in potato tubers cultivated in Jawa Barat. Along with the collection of potato tubers from the field, rhizosphere soil with healthy and diseased plant samples were also collected. Diluted soil suspensions were plated on nutrient agar. Based on the colony morphology, the bacterial isolates were purified. Dual culture of Cms vs. rhizosphere isolates, also Cms vs. endophytic bacterial isolates from infected tuber, were performed on nutrient agar to test the antagonism. Six out of 76 rhizosphere isolates (7.9%) and one endophyte isolate caused inhibition zone. Those isolates did not cause rot symptom when they were inoculated onto cut potato tuber, and they were considered as not plant pathogenic.