Anaerobic soil disinfestation efficacy against fusarium oxysporum is affected by soil temperature, and amendment type, rate and c:n ratio

Authors: SHRESTHA, UTSALA - University Of Tennessee; OWNLEY, BONNIE - University Of Tennessee; BRUCE, ALEX - University Of Tennessee; Rosskopf, Erin; BUTLER, DAVID - University Of Tennessee

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2020
Publication Date: 12/20/2020
Citation: Shrestha, U., Ownley, B., Bruce, A., Rosskopf, E.N., Butler, D. 2020. Anaerobic soil disinfestation efficacy against fusarium oxysporum is affected by soil temperature, and amendment type, rate and c:n ratio. Phytopathology. https://doi.org/10.1094/PHYTO-07-20-0276-R.
DOI: https://doi.org/10.1094/PHYTO-07-20-0276-R

Interpretive Summary: Fusarium oxysporum (Fo) and Fo f. sp. lycopersici (Fol) are important fungal plant pathogens of vegetable crops. A meta-analysis of anaerobic soil disinfestation (ASD) efficacy against Fusarium oxysporum (Fo) and Fo f. sp. lycopersici (Fol) was conducted to determine the effects of environment, organic amendment, and soil temperature on Fol inoculum survival. In a pot study, two organic amendments, dry molasses-based or wheat bran-based applied at 4 mg C/g soil, with 40:1, 30:1, 20:1, and 10:1 C:N ratios, were evaluated against Fol at 15-25°C. This was followed by a pot study at temperature regimes of 15-25°C and 25-35°C, and two C:N ratios (20:1 and 40:1), and a field study at 40:1, 30:1, 20:1, and 10:1 C:N ratios, 30:1 C:N ratio at lower C rate (2 mg C/g soil), and an anaerobic control. Soil temperature above 25°C, and more labile amendments, increased ASD suppression of Fo/Fol in the meta-analysis. In pot studies, Fol survival was reduced for molasses-based mixtures at 20:1 and 30:1 C:N ratios, compared to wheat bran-based, but not compared to the anaerobic control. At 25-35°C, all ASD treatments suppressed Fol relative to aerobic and anaerobic controls, further indicating that ASD suppression of Fol is strongly influenced by temperature. In the field, all ASD treatments reduced Fol survival compared to the anaerobic control. Amendment application at 4 mg C/g soil at 20:1 and 30:1 C:N ratios for ASD induces increased anaerobic soil conditions and higher mortality of Fol inoculum compared to lower C rates. Soil temperatures of at least 25-35°C improve treatment efficacy.

Technical Abstract: A meta-analysis of anaerobic soil disinfestation (ASD) efficacy against Fusarium oxysporum (Fo) and Fo f. sp. lycopersici (Fol) was conducted emphasizing effects of environment and organic amendment characteristics, and pot and field studies were conducted on ASD amendment C:N ratio and soil temperature effects on Fol inoculum survival. In a pot study, two organic amendments, dry molasses-based or wheat bran-based applied at 4 mg C/g soil, with 40:1, 30:1, 20:1, and 10:1 C:N ratios, were evaluated against Fol at 15-25°C. This was followed by a pot study at temperature regimes of 15-25°C and 25-35°C, and two C:N ratios (20:1 and 40:1), and a field study at 40:1, 30:1, 20:1, and 10:1 C:N ratios, 30:1 C:N ratio at lower C rate (2 mg C/g soil), and an anaerobic control. Soil temperature above 25°C, and more labile amendments, increased ASD suppression of Fo/Fol in the meta-analysis. In pot studies, Fol survival was reduced for molasses-based mixtures at 20:1 and 30:1 C:N ratios, compared to wheat bran-based, but not compared to the anaerobic control. At 25-35°C, all ASD treatments suppressed Fol relative to aerobic and anaerobic controls, further indicating that ASD suppression of Fol is strongly influenced by temperature. In the field, all ASD treatments reduced Fol survival compared to the anaerobic control. Amendment application at 4 mg C/g soil at 20:1 and 30:1 C:N ratios for ASD induces increased anaerobic soil conditions and higher mortality of Fol inoculum compared to lower C rates. Soil temperatures of at least 25-35°C improve treatment efficacy.