Gynoecious and monoecious cucumbers drive the assembly of different rhizosphere microbial communities

Cucumber sex expression is a key agronomic trait determining yield, but whether its formations is related to rhizosphere soil microbes remains poorly understood. This study compared the soil microbial community structures in rhizosphere between gynoecious and monoecious cucumbers to identify potential associations. The results showed that bacterial genera including Sphingomonas, and other unclassified taxa, were significantly enriched in the rhizosphere of the gynoecious plants. In contrast, members of Rokubacteriales and other taxa were significantly enriched in rhizosphere of monoecious cucumbers. For fungi, genera such as Aspergillus, Plectosphaerella, and Chaetomella were enriched in rhizosphere of gynoecious plants. Conversely, Trichoderma, Emericellopsis, Collariella, and Cordana were significantly enriched in monoecious cucumbers. Correlation network analysis revealed that the rhizosphere microbial network (especially the bacterial community) was more stable and displayed greater interspecific cooperation in monoecious cucumbers. Functional prediction revealed that multiple nitrogen-cycling processes of bacterial communities, including nitrification, aerobic nitrite oxidation, nitrite and nitrate ammonification, aerobic ammonia oxidation, and arsenate respiration were detected in rhizosphere of the gynoecious cucumbers. By contrast, hydrocarbon degradation functions, particularly those for aromatic and aliphatic non-methane hydrocarbons were significantly enriched in rhizosphere of monoecious cucumbers. Moreover, the rhizosphere of gynoecious plants harbored a higher abundance of saprotrophic and symbiotrophic fungi but a lower abundance of pathotrophic fungi compared with monoecious cucumbers. These findings demonstrate that the composition and potential functions of the rhizosphere microbiota differ between gynoecious and monoecious plants, indicating that soil microbes in rhizosphere play a role in the sex expression of cucumber varieties.