Date Published: February 16, 2018
Publisher: Public Library of Science
Author(s): Jia Zhao, Jiang Liu, Hong Liang, Jing Huang, Zhe Chen, Yuanjun Nie, Changbiao Wang, Yuguo Wang, Zhili He.
Bio-organic fertilizers (BOFs) combine functional microbes with a suitable substrate and have been shown to effectively suppress soil-borne diseases and promote plant growth. Here, we developed a novel bio-organic fertilizer (BOF) by fermentation of a cow plus chicken manure (M) compost using Fen-liquor Daqu (FLD) as a fermentation starter and compared the compositions of bacterial and fungal communities in the rhizosphere soil of watermelon plants after treatment with different fertilizers. Further, we aimed to explore the mechanisms underlying plant-promoting and disease (Fusarium wilt)-suppressing activities of each rhizosphere microbial community. The microbial communities of soil amended with cow plus chicken manure compost (S+M), soil amended with the BOF (S+BOF), and untreated control soil (S) without plants were analyzed through sequence analysis using the Illumina MiSeq platform. The results showed that a new microbial community was formed in the manure compost after fermentation by the Daqu. Application of the BOF to the soil induced remarkable changes in the rhizosphere microbial communities, with increased bacterial diversity and decreased fungal diversity. Most importantly, S+BOF showed the lowest abundance of Fusarium. Moreover, watermelon quality was higher (P < 0.05) in the S+BOF than in the S+M treatment. Thus, application of the BOF favorably altered the composition of the rhizosphere microbial community, suppressing Fusarium wilt disease and promoting plant quality.
In sustainable agriculture, which has been gaining increasing public as well as research interest, the soil is regarded a living system that is significantly affected by the microbial communities present . It is recognized that interactions among soil microbes can establish homeostasis of soil microbial communities, promote plant growth, and suppress soil-borne pathogens . In the rhizosphere, where the soil adheres to plant roots and is impacted by the roots and their exudates, complex biological and ecological processes, particularly plant–microbe interactions, occur [3–6]. This region hosts beneficial microbes as well as soil-borne pathogens, which are in competition . The rhizosphere community contains multiple species that exert beneficial effects on plant growth and health, such as nitrogen-fixing bacteria, mycorrhizal fungi, plant growth-promoting rhizomicrobes (PGPR), biocontrol microbes, and protozoa, while soil-borne pathogens that colonize the rhizosphere cause plant diseases by breaking the protective microbial shield and overcoming the plant’s innate defense mechanisms . The complexity and diversity of microbes in the rhizosphere are essential for maintaining homeostasis in the soil ecosystem [9, 10].
In our previous study, we found that continuous cropping of watermelon induces remarkably poor growth, high disease incidence, and low yield . While biological control using microbes is an effective and environmentally friendly strategy for controlling soil-borne fungal pathogens and promoting growth [32, 33], most studies have focused on individual microbial species, ignoring overall effects of microbial communities . In the current study, we applied Daqu-fermented BOF to soil with the aim to alter the microbial community to promote watermelon growth and control Fusarium wilt under continuous cropping.