Isolation and Genome Characterization of a Potentially Destructive Pathogen, Fusarium thapsinum, to Sorghum

Sorghum is the fifth most cultivated cereal; however, sorghum cultivation suffers from various threats. Fusarium thapsinum is the causal agent of sorghum stalk rot worldwide. However, there is no report on the genome characterization of F. thapsinum and its pathogenicity to sorghum glume. In this study, an F. thapsinum strain was isolated from the leaves and glumes of sorghum with red spot disease in Yibin, China. According to Koch's postulates, the strain was re-incubated on sorghum leaves and glumes. At 10 days postinoculation, red spots appeared, and the pathogen was re-identified as F. thapsinum and named FL-4, which indicated that F. thapsinum was pathogenic to sorghum leaves and glumes. The morphological characteristics of F. thapsinum in sorghum leaves were observed using scanning electron microscopy. Furthermore, genome sequencing indicated that the FL-4 genome assembly was 41.97 Mb with a GC ratio of 47.85%, N₅₀ 0.8 Mb, and 13,576 genes, including 1,124 secretory protein-coding genes and 5 antibiotic resistance genes. The basic characteristics of the genome were illustrated in a Circos map. Furthermore, all proteins were functionally annotated using the EggNOG, KEGG, GO, FVF, and PHI databases. This is the first report on the pathogenicity of F. thapsinum to sorghum glumes, as well as its genome characteristics. Considering the pathogenicity of F. thapsinum to sorghum and its broad appearance worldwide, F. thapsinum may be a destructive pathogen to sorghum, requiring greater attention. This research also provides a theoretical basis for further research on phytopathology.