The Impact of Continuous Cropping on Phenolic Acids in Muskmelon Soil and the Colonization of Trichoderma viride

Abstract

The obstacle associated with continuous cropping is an important problem in the production of muskmelon (Cucumis melo L.). The allelochemicals from root exudates play an active role in root–microbe communication. The primary objective of this study was to delve into the impact of root exudates and the continuous cultivation of muskmelon on the growth and colonization patterns of Trichoderma viride T23. It was observed that the root exudates of muskmelon significantly promoted mycelial growth and the sporulation of Trichoderma viride T23 at concentrations of 0.05, 0.1 g·mL−1, while at a concentration of 0.05 g·mL−1, the enzyme activities of β-glucosidase, chitinase and cellulase were 12.34, 13.23, and 17.85 U·mL−1, respectively, which were higher than those of the control. With increasing concentrations of root exudates, the hyphal growth, spore germination, and the three enzyme activities of Trichoderma viride T23 were decreased. The findings from the pot experiments revealed that the total phenolic acid content in the soil of replanted muskmelon demonstrated a trend of escalating over the course of the first growth cycle of continuous cropping to the fourth growth cycle of continuous cropping. The population density in the rhizosphere soil of Trichoderma viride T23 in the first growth cycle and the second growth cycle of continuous cropping shows a significant difference compared with other treatments, which led to statistically significant increments of stem diameter, leaf area, fresh weight, dry weight and SPAD index. It is necessary to increase the dose of the beneficial microorganism or degrade the phenolics in the rhizosphere soil to promote effectiveness while increasing the growth cycles of continuous cropping.