Neoscytalidium dimidiatum associated with Albizia lebbeck disease in Saudi Arabia: Symptomatology, pathogenicity and molecular identification

Botryosphaeriaceae fungi cause infections that generate disease symptoms in plants in extreme environments. The present study identified the causal agent of dieback disease on lebbeck trees in Saudi Arabia. Albizia lebbeck trees showed widespread dieback, decline and cracking symptoms of samples taken during a Qassim University, Saudi Arabia survey. The survey showed that over 80% of lebbeck trees showed wilted roots, stem cankers and death of wilted trees. Fungal colonies were obtained from symptomatic tissues cultured on water agar for 3 weeks at 25°C. Elongation factor alpha (EF1-728 F, AL33R), ITS (ITS4) and LSU (128) regions of the rDNA operon and the partial beta-tubulin gene (tub2; Bt2aF, Bt2bR) were sequenced for molecular identification. Based on morphological and molecular characterization, the pathogen was identified as Neoscytalidium dimidiatum. During the pathogenicity investigation, the fungus re-isolated from the infected seedlings expressed the same morphological characteristics on the culture media as the N. dimidiatum isolate. A host range study involving six tree species inoculation with N. dimidiatum caused wilting and death in three plants. To our knowledge, this study is the first to report on N. dimidiatum in Saudi Arabia.