Paddy soil virus diversity in red soil region under organic fertilization and its effects on biogeographical carbon cycle

【Objective】To explore the diversity,community structure and differences of soil viruses in paddy fields under different organic fertilization conditions,and to provide a theoretical basis for revealing coevolutionary relationship between viruses and their host,as well as the process of viral-microecosystems-driven biogeographical carbon cycle.【Method】The long-term localization trial began in 1981 and set up 6 treatments with 3 replicates foreach.Field experiment comprised of 6 treatments:(1)CK,no fertilizer,(2)NPK,single chemical fertilizer,(3)M1,green manure at early rice,(4)M2,green manureat early rice+pig manure at early rice,(5)M3,green manure at early rice+pig manure at late rice,(6)M4,green manure at early rice+straw returning at late rice.After the late harvest of rice in 2020,the topsoil(0-20 cm)was collected to determine macro-virus groupand nutrient contentin the soil by means of the macro-virus sequencing platform and soil routine analysis.【Result】Soil viruses were distributed in 37 families in red soil region,and Microviridae was the main virus group.Abundance of Siphoviridae,Myoviridae and Poxviridae in M3 treatment was significantly higher than that in other treatments(P<0.05,the same below).Abundance of Microviridae and Nanoviridae in M2 treatment were significantly higher than that in other treatments.Through metagenomic gene annotation of the rice field soil virus,143 unique carbohydrate transport and metabolism genes were identified.46 open reading frames belonged to 13 virus-assisted carbohydrate-active enzymes(CAZyme),of which glycoside hydrolases were the most abundant,accounting for 61.7%,followed by glycosyl transfer enzyme.The study also found that abundance of soil virus species could reflect soil pH,Mg²⁺and rice yield to a certain extent.Virus community structure was driven by pH,Mg²⁺and other factors.【Conclusion】Microviridae is the main virus group in the paddy soil in the red soil area.The application of pig manure significantly changes the community structure and species composition of soil viruses,and the virus community structure is significantly affected by soil pH and Mg²⁺content.CAZyme genes are detected in the virions through metagenome gene annotation of paddy soil virus,belonging to carbohydrate esterase and glycosidyltransferase,respectively.Virally-encoded accessory metabolic genes or metabolic genes alter bacterial metabolism and indirectly contribute to bio-Earth carbon cycling of agricultural soils.