Neofusicoccum parvum: A NOVEL PATHOGEN SPECIES CAUSING WILTED LEAF AND DIEBACK PETIOLES ON LOTUS (Nelumbo nucifera) IN THUA THIEN HUE, VIETNAM

Lotus (Nelumbo nucifera) is an essential species in many countries. In Vietnam, the lotus is a plant with cultural and spiritual significance, representing purity, spiritual growth, and enlightenment. However, petiole dieback and wilted dry leaves are severe diseases that weaken the host and decrease leaf photosynthesis, reducing lotus production. In this study, a new dieback and wilted leaf pathogen were identified via its morphology, phylogeny, and pathogenicity. Four representative Botryosphaeriaceae isolates from lotus fields in Hue, Phong Dien, and Phu Loc were selected for identification and pathogenicity testing. Based on morphological and phylogenetic analyses and by using the ribosomal internal transcribed spacer region (ITS) and β-tubulin (tub-2) gene sequences, we identified four isolates as Neofusicoccum parvum. In the pathogenicity test, typical symptoms appear on the inoculated lotus petioles, including dieback, curving, and wilted leaves. These symptoms are consistent with those observed in the field. In addition to identifying the pathogen species responsible for lotus disease, this study provides valuable insights into the taxonomy and phylogenetic relationships of new fungal pathogens that affect lotus fields. These findings can contribute to effective management strategies to control these diseases and improve lotus production. To the best of our knowledge, this is the first report of characterization and phylogenetic analysis of N. fusicoccum as the causal agent of wilted leaves and dieback disease in Thua Thien Hue, Vietnam.