Chitosan reduces naturally occurring plant pathogenic fungi and increases nematophagous fungusPurpureocilliumunder field soil conditions

Abstract

Chitosan reduced soil pH, conductivity (CE) and cation exchange capacity (CEC) in pots when applied at field capacity. However, chitosan did not affect these soil physicochemical properties, when applied monthly to agricultural fields. Chitosan did not affect field respiration. Increases in field soil respiration found in chitosan plots, especially in spring-midsummer, were not significant. Although, no differences in soil mineral nitrogen were found, chitosan influenced field soil microbiota. Metabarcoding showed chitosan significantly modifies fungal genera composition of ecologically managed field soil. On the contrary, chitosan caused no significant differences in bacterial taxa composition of field soil. Chitosan coacervates increase naturally occurring nematophagous fungusPurpureocilliumin soil respect to chitosan solution treated soil and untreated controls. Besides chitosan reduces inoculum of plant pathogenic fungiAlternariaandFusariumin field soil. Soil microbial co-occurrence network analysis clustering coefficient (CC) for ITS+V1-V2 regions show that the nematophagous fungusPochoniapromoted network clustering into modules. In addition, CC in ITS+V3-V4 regions show that the nematode trapping-fungusOrbiliaand bacteria belonging toAcidimicrobialesandCytophagalesalso significantly contributed to microbial network clustering in field soil. Our results show that chitosan coacervates increase soil nematophagous microbiota and that both nematode egg-parasites and trapping-fungi help to structure soil microbiota.