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Anaerobic soil disinfestation enhances endemic soil populations of Trichoderma

Utsala Shrestha: University of Tennessee, Plant Sciences

<div><span>Quantification of <em>Trichoderma</em> spp. in soil treated with anaerobic soil disinfestation (ASD) revealed that endemic soil populations of <em>Trichoderma</em> increased after treatment. Treatments included a sandy clay loam soil amended with labile carbon (C rate of 4 mg C/g soil at a C:N ratio 30:1), <em>Trichoderma harzianum</em> (RootShield) with and without labile C amendment, and a non-amended control. All treatments were irrigated and tarped with polyethylene at treatment initiation. After three weeks, soil was sampled at a 0- to 5-cm depth of each pot and stored at 4</span>°<span>C until analysis. Serial dilutions were used to quantify <em>Trichoderma</em> spp. on <em>Trichoderma</em>-selective medium. Soil DNA was extracted and Internal Transcribed Spacer (ITS) region copy number of <em>T. harzianum</em> in the soil DNA was quantified using Taqman qPCR. ASD treatments significantly enhanced populations of endemic <em>Trichoderma</em> spp. with the highest CFU (4.6 log CFU+1/g soil) as compared to the non-amended control (4.3 log CFU+1/g soil), while <em>T. harzianum</em> amended soil alone did not significantly increase total populations of <em>Trichoderma</em> spp. Quantification by qPCR indicated the highest ITS region copies of <em>T. harzianum</em> per milligram of soil in RootShield-amended soil; at the same time, endemic <em>T. harzianum</em> in ASD-treated soil was more than two-fold higher than the unamended control. Enhanced soil populations of endemic <em>Trichoderma</em> by ASD treatment may be an important mechanism of plant pathogen suppression by ASD.</span></div>