Genome‐Enabled Characterisation of Fusarium sacchari as a Novel Root Rot Pathogen of Coconut

Abstract

Coconut ( Cocos nucifera ) production is increasingly constrained by root rot diseases, yet the involvement of specific Fusarium species remains poorly understood. This study focused on root rot‐infected coconut plants from Tamil Nadu, India, aiming to isolate and characterise the causal pathogen using morphological, molecular, pathogenicity and genomic approaches. Isolates CF1 and CF8 displayed characteristic features of Fusarium , including 1‐septate microconidia, 3‐ to 5‐septate macroconidia, and globoid chlamydospores. Pathogenicity assays confirmed the causal association of both isolates, with root rot symptoms developing 20 days after inoculation, resulting in 58.3% and 66.7% disease incidence and significantly reduced root weight compared with healthy controls. Koch's postulates were fulfilled through successful reisolation and identification of the pathogen. Multilocus phylogenetic analysis based on ITS, tef1‐α and RPB2 sequences identified both isolates as Fusarium sacchari , sharing 99.0%–99.8% sequence identity with authenticated reference strains. Whole‐genome sequencing of isolate CF8 generated a 42.70 Mb assembly with 96.7% BUSCO completeness, providing insights into genes associated with carbohydrate metabolism, transcriptional regulation and virulence. This study is the first report of F . sacchari as the causal agent of coconut root rot, thereby expanding the known host range of this pathogen and providing a foundation for future studies on its biology, epidemiology and disease management.