Effects of continuous melon cropping on rhizospheric fungal communities

Long-term continuous cropping of crops leads to soil degradation and a decrease in crop yield and quality. Continuous cropping obstacles are common with melon; however, the rhizosphere microbial community response to continuous cropping of melon remains poorly investigated. Here, we comparatively investigated the structure and function of the rhizospheric fungal community from melon greenhouses replanted for 0, 1, 2, and 3 years (CK, 1a, 2a, and 3a, respectively) using high-throughput absolute quantification sequencing. The results showed that the fungal abundance increased with continuous cropping duration, but the fungal diversity and richness decreased. The most dominant phyla were Ascomycota and Basidiomycota, and their absolute abundance increased continuously. At the genus level, Fusarium, Thanatephorus, and Plectosphaerella were the dominant genera, and their absolute abundance increased significantly (p < 0.05) with the continuous cropping duration. FUNGuild function prediction showed that continuous cropping caused the accumulation of endophyte-plant pathogens and plant pathogens, which may accelerate soil-borne diseases of melon. Our results provide guidance for revealing the mechanism of continuous cropping obstacles in melon, which is important in evaluating the sustainability of this agricultural practice.