Association of Neofusicoccum parvum with leaf scorch on Cinnamomum cassia in China

Abstract

Leaf spot, caused by Neofusicoccum parvum, is an important disease limiting the growth of Chinese cinnamon (Cinnamomum cassia) in the field. This disease was first observed in Deqing (Guangdong Province, China) in 2018, manifesting as circular or irregularly shaped necrotic lesions along the leaf margins and tips, enlarging to irregular lesions with numerous black dots. Representative isolates were isolated from affected leaves and identified based on morphological characteristics and phylogenetic analyses of the internal transcribed spacer (ITS) region, the translation elongation factor 1α (EF1α) gene and a portion of the β-tubulin gene (TUB2). Colonies were initially white on PDA, turning grey-black after 7 days. The conidia were fusiform to oval, hyaline, thinwalled with rounded apices and truncate bases. The pathogen was placed in the same clade as Neofusicoccum parvum in phylogenetic trees constructed using concatenated sequences of ITS, EF1α and TUB2 genes. Based on morphological and phylogenetic data, the pathogen was identified as N. parvum. On infected leaves, Koch's postulates were fulfilled, and the same pathogen re-isolated. To our knowledge, this is the first report of N. parvum causing disease on Chinese cinnamon worldwide.