Pathogenicity and Virulence of <i>Fusarium oxysporum</i> f. sp. <i>vasinfectum</i> Race 4: Understanding an Emerging Threat to Cotton from Field to Genome

<i>Fusarium oxysporum</i> f. sp. <i>vasinfectum</i> race 4 (<i>Fov</i>4) is a highly virulent pathogen threatening cotton production globally, particularly in the US. This review synthesizes current knowledge of <i>Fov</i>4 biology, pathogenesis, and genomic features that drive host specificity and virulence. <i>Fov</i>4 life cycle, infection mechanisms, environmental factors influencing disease, and host resistance in Pima and Upland cotton varieties are discussed. Genomic resources reveal that <i>Fov</i>4 genomes are larger and more repeat-rich than those of several other <i>Fov</i> races, although chromosome-scale core versus accessory architecture remains unresolved. Studies have identified candidate race-specific virulence factors, including race-specific SIX effectors and secondary-metabolite genes in <i>Fov</i>4 and related <i>Fov</i> races. Challenges remain in managing cotton diseases caused by <i>Fov</i>4 due to its soil persistence and genetic adaptability. Integrated management combining resistant varieties, cultural practices, and precision monitoring ensures sustainable disease control, while advancing knowledge of <i>Fov</i>4 virulence mechanisms enhances future management strategies through innovative approaches.