First report of Didymella leaf blight on Cornus officinalis caused by D. glomerata in China

Cornus officinalis (Chinese cornel dogwood) is a traditional valuable Chinese medicinal plant. In May 2011, a leaf blight was found on C. officinalis in the Taiping township (33o37´48˝N, 111o43´39˝E) of Xixia county, Nanyang city, China. The disease occurred mainly in the summer season especially following rainy days, with foliar disease incidence of 52 to 86% (n=300). Initially, water-soaked lesions were seen at the leaf tip (occasionally leaf base) of affected plants. The lesions developed from the leaf tips towards the leaf base, and turned brown as the tissues dried-up. The diseased tissues were taupe with multiple tiny black granules (pycnidia) under high humidity conditions. Diseased tissue pieces sampled from lesion borders were surfaced sterilized in 75% ethanol for 10 s, followed by 3 min in 0.1% HgCl2, rinsing 3 times with sterile water, and plating on potato-dextrose-agar (PDA). Didymella sp. cultures were predominantly isolated from the surface-disinfected lesions. Two strains (A13 and H-1) we...