Abstract
Fusarium stalk rot (FSR) caused by Fusarium graminearum (FG) significantly affects the productivity of maize grain crops. Application of agrochemicals to control the disease is harmful to environment. In this regard, use of biocontrol agent (BCA) is an alternative to agrochemicals. Although Trichoderma species are known as BCA, the selection of host-pathogen specific Trichoderma is essential for the successful field application. Hence, we screened a total of 100 Trichoderma isolates against FG, selected Trichoderma harzianum (CCTCC-RW0024) for greenhouse experiments and studied its effect on changes of maize rhizosphere microbiome and biocontrol of FSR. The strain CCTCC-RW0024 displayed high antagonistic activity (96.30%), disease reduction (86.66%), biocontrol-related enzyme and gene expression. The root colonization of the strain was confirmed by eGFP tagging and qRT-PCR analysis. Pyrosequencing revealed that exogenous inoculation of the strain in maize rhizosphere increased the plant growth promoting acidobacteria (18.4%), decreased 66% of FG, and also increased the plant growth. In addition, metabolites of this strain could interact with pathogenicity related transcriptional cofactor FgSWi6, thereby contributing to its inhibition. It is concluded that T. harzianum strain CCTCC-RW0024 is a potential BCA against FSR.
Highlights
Maize (Zea mays) is an important grain crop for human food security, fodder, and biofuel production
Among the 100 isolates, the top ten potent isolates were selected for further experiments with high antagonist activity against Fusarium graminearum (FG) such as T. asperellum strain CCTCC-SBW0102 (92.3%), T. aureoviride strain CCTCC-SBW0005 (85.2%), T. harzianum strain CCTCC-SBW0101 (89.2%), T. asperellum strain CCTCC-SBW0109 (93.4%), T. asperellum strain CCTCCSBW0013 (77.4), T. asperellum strain CCTCC-SBW0052 (92.1%), T. asperellum strain CCTCC-SBW0091 (82.50%), T. tawa strain CCTCC-RW0023 (90.20%), T. harzianum strain CCTCC-RW0024 (96.3%) and T. harzianum strain CCTCC-SBW0181 (82.35%) (Supplementary Table 1)
The results revealed that exogenous inoculation of T. harzianum strain CCTCC-RW0024 could significantly increase the plant growth, plant biomass and reduce the pathogen attack.Similar results are found in the work of Akladious and Abbas[32]
Summary
Maize (Zea mays) is an important grain crop for human food security, fodder, and biofuel production. The input of the agrochemicals to the environment is proved to be harmful to beneficial microbiomes and considerably change the human attitude[3] In this regard, it is obligatory to search for an alternative eco-friendly microbial source to prevent the plant disease. Trichoderma spp., are globally known as BCAs and used to prevent plant pathogens and increase plant immunity in field and greenhouse conditions[4] This is because of their ability in beneficial interactions with plants (maize, cotton, cucumber) through production of auxin like compounds and secondary metabolites[5,6,7]. The use of pathogen-specific microbial BCAs has advantage to prevent the particular pathogen and to increase the beneficial rhizosphere microbiome and plant immunity. We applied a molecular docking method to predict the inhibitory effect of T. harzianum metabolites on pathogenicity related transcriptional cofactor FgSWi6 of FG
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