Genetic Diversity and Pathogenicity of Fusarium fujikuroi Species Complex (FFSC) Causing Sugarcane Pokkah Boeng Disease (PBD) in China

Pokkah boeng disease (PBD), a sugarcane foliar disease, is caused by various Fusarium spp. within the Fusarium fujikuroi species complex (FFSC). In the current study, we investigated the diversity of Fusarium spp. associated with PBD in China. In total, 320 leaf samples displaying PBD symptoms were collected over 10 consecutive years (2012 to 2021), during winter and summer, from six various sugarcane-growing regions (Guangxi, Yunnan, Guangdong, Zhejiang, Hainan, and Fujian) in China. Phylogenetic analysis of Fusarium spp. was reconstructed using translation elongation factor 1-α, and DNA-directed RNA polymerase II largest subunit and second-largest subunit multigene sequences. Evolutionary studies of these regions categorized the isolates into four FFSC species (F. sacchari, F. proliferatum, F. verticillioides, and F. andiyazi). The identified isolates, which developed irregular necrotic patches and rotting symptoms on the sugarcane plant after approximately 30 days were tested for their pathogenicity. Symptoms that appeared during pathogenicity testing were consistent with those observed under field conditions. Each strain of the pathogenic Fusarium spp. belonged to different vegetative compatibility groups (VCGs), and there was no affinity between VCGs. Our results contribute to understanding FFSC and accurately identifying Fusarium spp. associated with the sugarcane crop.