A novel key virulence factor, FoSSP71, inhibits plant immunity and promotes pathogenesis in <i>Fusarium oxysporum</i> f. sp. <i>cubense</i>

<i>Fusarium</i> wilt of banana (<i>Musa</i> spp.), caused by <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (<i>Foc</i>), poses a significant threat to the global banana industry. Particularly, tropical race 4 of <i>Foc</i> exhibits high pathogenicity toward the major commercial banana cultivar Cavendish, and there are no effective control measures available. Here, we characterize a novel effector protein, FoSSP71, from <i>Foc</i>, which was significantly induced during the early stages of the <i>Foc</i>4 banana interaction and could suppress BAX-triggered programmed cell death in <i>Nicotiana benthamiana</i>. Transient expression of <i>FoSSP71</i> in <i>N. benthamiana</i> leaves could weaken the upregulation expression of genes involved in the SA signaling pathway induced by flg22 and significantly reduce both reactive oxygen species bursts and callose accumulation. To verify the function of FoSSP71, a <i>FoSSP71</i> deletion mutant was created. The <i>FoSSP71</i> deletion mutant displayed a reduced growth rate in <i>F. oxysporum</i> and a marked reduction in virulence toward bananas compared to the wild type (WT). Furthermore, the expression levels of <i>PR3</i> and <i>PR10</i> were significantly downregulated in bananas infected with the <i>ΔFoSSP71</i> strain compared to bananas infected with the WT strain. These findings indicate that FoSSP71 is essential for <i>Foc</i>4 pathogenicity and plays a key virulence role during <i>Fusarium</i> invasion. Therefore, FoSSP71 presents a potential target for future <i>Fusarium</i> wilt control, offering a scientific foundation for breeding disease-resistant banana varieties and developing novel control measures.IMPORTANCEEffector proteins are critical virulence factors for fungi, playing essential roles during the fungal infection of plants. In this study, we identified a novel effector protein, FoSSP71, which is an important regulatory protein involved in the invasion of bananas by <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> race 4 (<i>Foc</i>4). Understanding its regulatory mechanisms is necessary. Our research indicates that FoSSP71 is an essential virulence factor for <i>Foc</i>4, as it suppresses plant immune responses by inhibiting the accumulation of reactive oxygen species and callose. The <i>Foc</i>4 mutant lacking <i>FoSSP71</i> showed significantly reduced pathogenicity toward bananas, demonstrating that FoSSP71 is a potential target for controlling banana wilt disease. These findings provide a scientific basis for breeding banana varieties resistant to wilt disease and for developing new disease control strategies, which are crucial for the sustainable development of the global banana industry.