Effect of Soil-borne and Tuber-borne Inoculum Density of Rhizoctonia solani Kühn on Black Scurf Development and Tuber Yield of Potato

Black scurf of potato caused by Rhizoctonia solani Kühn is an important soil-borne disease that reduces tuber yield and quality. The present study was conducted to evaluate the influence of soil-borne and tuber-borne inoculum density of R. solani on black scurf development in potato. The experiment was carried out under pot conditions during two consecutive years. For soil-borne inoculum, five potato cultivars viz., Kufri Ashoka, Kufri Chandramukhi, Kufri Pukhraj, Kufri Jyoti and Kufri Sinduri were tested with three inoculum levels (6 g, 12 g and 18 g) along with control. For tuber-borne inoculum, six inoculum levels (0%, 5%, 10%, 20%, 40% and 80%) were evaluated using Kufri Jyoti. Results revealed that disease incidence and severity increased significantly with increasing inoculum density in both soil-borne and tuber-borne inoculum experiments. Among cultivars, Kufri Pukhraj recorded maximum disease incidence and severity, whereas Kufri Sinduri showed comparatively lower disease development. Maximum disease incidence and severity were observed at 18 g soil inoculum and 80% tuber inoculum levels. The findings indicated that higher inoculum density enhanced disease development and varietal differences in susceptibility were evident. The study highlights the importance of reducing inoculum load and using tolerant cultivars for effective management of black scurf disease in potato.