Effects of Nutrient Accumulation and Microbial Community Changes on Tomato Fusarium Wilt Disease in Greenhouse Soil

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici has severely threatened sustainable greenhouse tomato production. However, the effects of nutrient enrichment due to excessive fertilization on Fusarium wilt remain unclear. This study aimed to investigate the relationships among soil nutrient enrichment, microbial community structure, and the occurrence of Fusarium wilt under greenhouse conditions. This study used chemical analysis and microbiological techniques to analyze rhizosphere soil samples from greenhouse tomato production areas with varying degrees of Fusarium wilt. The results showed that, as compared with the Health group, the rhizosphere soil of Disease group has a significant nutrient enrichment, which significantly influences bacterial diversity and structure. Particularly when soil NO3−–N content exceeds 170.43 mg kg−1, there was a significant reduction in the relative abundance of key biocontrol bacteria such as Bacillus and Lysinibacillus. This reduction indirectly contributes to an increase in Fusarium oxysporum abundance, subsequently elevating the likelihood of pathogen infection. Furthermore, the Disease group also exhibited a simplified co-occurrence network with a 22.37% reduction in competitive interactions between bacteria and fungi. These changes might collectively increase the risk of tomato Fusarium wilt infection. Meanwhile, the relative abundance of bacteria carrying antibiotic resistance genes significantly increased in the Disease group, which also reduced soil resistance. Together, the results presented here not only uncover the effect of long-term excessive fertilization on the occurrence of Fusarium wilt but also advance our understanding of the interactions among soil nutrient management and microbial communities in the tomato rhizosphere, which provides a scientific basis for formulating strategies to prevent soil-borne diseases in greenhouse tomatoes.