Soil viruses regulate soil nutrient cycling through themselves and their effects on host functioning to impede the growth of continuously planted Casuarina equisetifolia

Casuarina equisetifolia (C. equisetifolia) is an economically important forest tree, and continuous planting has led to changes in soil microbial diversity and function in the rhizosphere of C. equisetifolia, with a decrease in wood volume of >29.0 %, which has constrained the sustainable development of the industry. Viruses regulate soil microbial diversity, nutrient cycling, fertility, and consequently plant growth. In this study, C. equisetifolia with different numbers of continuous plantings was used as research object, and macroviromics techniques were used to analyze the reasons why soil viruses regulate soil nutrient cycling and thus impede the growth of C. equisetifolia in continuous plantings through their own and their effects on host function. It was shown that continuous planting led to a significant increase in the abundance of 10 characteristic viruses of module 1 in the rhizosphere soil of C. equisetifolia. After parasitizing the host microorganisms, these characteristic viruses reproduced by lysis, and at the same time contributed to a significant decrease in soil microbial biomass carbon, nitrogen and respiration intensity, a significant decrease in soil nutrient cycling and resistance-related enzyme activities, which in turn led to a decrease in available nitrogen, phosphorus and potassium contents of the soil, as well as a significant decrease in the plant height, root length and dry weight of C. equisetifolia. It can be seen that the reproduction mode of the characteristic viruses affects the host number and function, reduces the supply of soil nutrients, and hinders the growth of C. equisetifolia after continuous planting. This study reveals for the first time the different roles of viral propagation strategies in continuous planting and provides a new paradigm for the study of “virus-microbe-plant” interactions.