Deciphering the Fusarium-wilt control effect and succession driver of microbial communities managed under low-temperature conditions

The regulation of microbial communities is an important strategy to control the spread of soil-borne diseases. However, the control of soil-borne diseases through the regulation of microbial communities at low-temperature conditions, and the association of their succession with abiotic factors during plant cultivation are not well characterised. In this study, the effects of various soil-disinfestation strategies, i.e. soil irrigated to saturation (SA), reductive soil disinfestation (RSD) and ammonia fumigation (AF), on the prevention of watermelon Fusarium wilt as well as the interaction of microbial community succession and abiotic factors were determined. The abundance of F. oxysporum in soil samples subjected to SA, RSD and AF treatments decreased significantly by 86.09%, 90.67% and 93.68%, respectively, compared with the untreated soil sample. RSD and AF treatments established significantly different microbial alpha- and 13-diversities and physicochemical properties, whereas SA treatment showed no significant effect on these properties. After planting, RSD- and AF-treated soils exhibited significantly reduced disease incidence and increased the watermelon yield, respectively, whereas SA-treated soil showed no significant effects. The physicochemical and microbial characteristics of treated soils were similar to those of untreated diseased soil. Moreover, the differences in soil physicochemical characteristics remarkably and positively correlated with the dissimilarities in microbial communities. For the differences in bacterial and fungal 13-diversities, soil pH was determined to have the highest mean predictor importance value. Potentially beneficial microbes were identified mainly after RSD and AF treatments; however, the relative abundances of these microbes were closely associated with soil pH and significantly decreased after planting. Overall, the soil-borne pathogens reduced and microbial community improved by RSD and AF treatments at low-temperature conditions could effectively control soil-borne diseases. Soil pH plays a pivotal role in restoring the microbial community during watermelon cultivation.