Identification of Corynespora cassiicola causing leaf spot on Syringa species.

Lilacs (Syringa spp.), a genus of trees and shrubs in the Oleaceae, are known for their beautiful, fragrant flowers and are widely cultivated as ornamentals. In September 2017, a new leaf spot disease was observed on S. oblata in the Sui and Tang Ruins Dynasties Botanical Garden in Luoyang, Henan Province, China. Leaf symptoms appeared as small brown lesions at earlier stages, which with age turned into suborbicular brown, faintly zonate and depressed. Fully mature lesions were mostly irregular to circular, concentric rings with taupe and dark brown bands. A total of 12 monoconidial isolates were obtained from S. oblata showing leaf symptoms. Colonies were grey to light brown and darker underneath on potato dextrose agar. Based upon morphological characteristics and multilocus phylogenetic analyses using ITS, TEF1 and RPB2 loci, isolates were identified as Corynespora cassiicola. Pathogenicity tests on leaves produced symptoms matching those described above and the fungus was re‐isolated, confirming Koch's postulates. This study represents the first report of C. cassiicola on lilacs in China. [ABSTRACT FROM AUTHOR]