PCR-based detection and pathogenicity assessment of Stilbocrea banihashemiana in pomegranate orchards

Abstract Canker disease poses a significant economic threat to pomegranate orchards worldwide, leading to considerable yield losses and tree decline. Recent host range studies have identified Stilbocrea banihashemiana , a newly discovered canker-causing fungal pathogen, as a potential agent of this disease. Between 2023 and 2025, 161 wood tissue samples (108 symptomatic and 53 asymptomatic) were collected from six pomegranate orchards across four distinct regions of Fars Province, Iran. PCR assays utilizing four species-specific primer sets confirmed the presence of S. banihashemiana in 43.5% of symptomatic samples, often with mixed fungal infections. The TEF-Sb1 and TEF-Sb4 primer sets demonstrated superior detection efficiency. Notably, latent infections were detected in 10% of asymptomatic samples, indicating a latent phase of the pathogen. Traditional culturing yielded 26 isolates from PCR-positive samples, further validating the molecular results. Pathogenicity assessments showed considerable differences in aggressiveness among these isolates. Principal component analysis based on three pathogenicity traits identified three clusters of aggressiveness: high, moderate, and low. Furthermore, the evaluation of cultivar susceptibility based on six pathogenicity traits revealed that the commercially important cultivar ‘Rabab-e-Neyriz’ was the most susceptible, while ‘Bihaste Ravar’ showed relative resistance. The ability of S. banihashemiana to colonize both symptomatic and asymptomatic tissues, along with its diverse virulence strategies, underscores its potential as an emerging threat to pomegranate production. This study represents the first global report of S. banihashemiana associated with canker and dieback in pomegranate, highlighting its potential role in exacerbating fruit tree epidemics, particularly under changing climate conditions.