Effects of biological agents on soil microbiology, enzyme activity and fruit quality of kiwifruit with root rot

Context. Root rot is common for kiwifruit (Actinidia chinensis var. diliciosa) plants. It is not easily controlled by chemical methods, and biological agents are an alternative. Aims. This study investigated the effects of biological agents on the activity and diversity of soil microorganisms, soil enzyme activity and physicochemical indices during the growth period of kiwifruit plants. Methods. There were four treatments: (1) root-rot plants applied with traditional fertiliser (RP); (2) root-rot plants applied with biological agents CY (CY); (3) root-rot plants applied with biological agents CL (CL); and (4) healthy plants with traditional fertiliser (HP). Most samples were taken during the growth period of kiwifruit plants, while activities of defensive-related enzymes and quality of kiwifruits were tested in the fructescence period. Key results. CY and CL treatments significantly improved microbial activity, changed microbial structure, increased the diversity, richness and uniformity of microbial species, and altered the relative utilisation ratio of six carbon sources. Soil nutrients of kiwifruit plants with root rot improved with CY and CL compared to RP. Health of kiwifruit plants with CY and CL also improved compared to RP. Activities of defensive-related enzymes in CY and CL treatments were significantly higher than in RP treatment (P < 0.05). Fruit quality indices were also higher than RP. Conclusions. CY and CL changed the microbial communities in soil, and improved soil nutrients and plant health. Implications. By altering the soil microbial structure, biological agents used to control root rot in kiwifruit plants improved tree health and fruit quality, and provide an alternative to chemical control of root rot.