Aggressiveness of Rhizoctonia solani Strains against Potato Varieties and Integrated Management of Black Scurf Disease

Black scurf has become the predominant potato disease in Gilgit-Baltistan (GB), causing substantial economic losses due to reduced tuber quality and yield. In this study we have assessed the aggressiveness of twenty strains of Rhizoctonia solani (RS1–RS20) against six potato varieties (Desiree, Diamond, Cardinal, Muroto, and Lady Rosetta) and tested integrated management strategies for disease control. In the first experiment, black scurf incidence and disease severity were used to evaluate the aggressiveness of R. solani strains. The results showed considerable variability among the strains, but none of them showed complete pathogenicity or destroyed all test plants. Potato varieties responded differently to infection, with ‘Desiree’ being the most susceptible and Muroto the least affected. In the second experiment, two types of field trials were carried out: (i) healthy potato tubers planted in artificially infected fields and (ii) naturally infected tubers grown under field conditions. In both studies, tubers were treated before planting with either T1 (botanical extracts + Trichoderma harzianum) or T2 (botanical extracts + T. viride). T1 has consistently been shown to be more effective than T2 in reducing the severity of black scurf. The findings underline the importance of integrating resistant varieties with biocontrol-based treatments in order to improve disease management, profitability, and food security in the GB region. Keywords: Potato varieties, R. solani , black scurf, management, Gilgit-Baltistan