Potato black scurf and stem canker: Pathogen biology, global distribution, traditional and modern diagnostics

Rhizoctonia solani is a soil- and seed-borne fungus, manifesting as black scurf and stem canker disease, resulting in substantial yield and quality losses globally. This fungus reproduces asexually through hyphae and sclerotia. Its genetic diversity is organized into 14 anastomosis groups (AGs), with AG3-PT being the predominant group on potato. Global trade of seed potatoes, though vital for agricultural development, inadvertently transmits the pathogen across regions. Disease development is influenced by environmental and agronomic factors, leading to severe outbreaks and economic impact. Accurate diagnosis is challenging due to the pathogen's genetic complexity, necessitating a transition from traditional culture-based and biochemical methods to molecular, genomic, and emerging digital technologies. Methods such as PCR, isothermal amplification, sequencing, sensor-based biosensing, and AI-driven imaging have improved the detection, quantification, and non-invasive monitoring of the pathogen. Combining these diagnostic methods into a tiered framework provides prospects for efficient disease surveillance, informed management decisions, and sustainable potato production systems.