Volatile fatty acid concentration, soil pH and soil texture during anaerobic soil conditions affect viability of Athelia (Sclerotium) rolfsii sclerotia

Swilling, Keagan J.; Shrestha, Utsala; Ownley, Bonnie H.; Gwinn, Kimberly D.; Butler, David M.

doi:10.1007/s10658-021-02392-8

Cited by 8 publications

(5 citation statements)

References 33 publications

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“…Studies by Tenuta et al (2002) and Abbasi et al (2009) indicated that VFAs reduced numbers of microsclerotia of V. dahliae after several days, and the effect was more pronounced at lower soil pH. Similarly, Swilling et al (2021) reported that soil pH and soil texture affected the antifungal activity of VFAs against A. rolfsii in autoclaved soils under laboratory conditions. The pKa values for both acetic and n-butyric acids are near 4.8 so in an acidic soil, a larger ratio of the VFAs would be in a non-dissociated state.…”

Section: Introductionmentioning

confidence: 91%

Mechanisms of Anaerobic Soil Disinfestation: Volatile Fatty Acids Reduce Viability of Athelia (Sclerotium) rolfsii Sclerotia in Acidic Soil Conditions and Have Limited Effects on Endemic Trichoderma spp.

Swilling

Shrestha

Ownley

et al. 2021

Front. Sustain. Food Syst.

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Volatile fatty acids (VFAs), such as acetic and n-butyric acid, released during anaerobic decomposition of organic soil amendments during anaerobic soil disinfestation (ASD) likely play a role in soilborne plant pathogen inoculum suppression. However, research is limited on the direct effects of soil VFA exposure on fungal plant pathogen inoculum, effects on pathogen antagonists such as Trichoderma spp., and the role of soil microbial VFA metabolism on reducing exposure effects. The present study addresses these limitations through a series of studies evaluating the effects of VFA (acetic or n-butyric acid), VFA concentration (4, 8, or 16 mmol/kg soil), soil sterilization by autoclaving, and soil amendment on the viability of Athelia rolfsii (Sclerotium rolfsii) sclerotia post VFA exposure, and soil populations of Trichoderma spp. HCl and water-only controls were included. After 4-days exposure in an acidic, anaerobic environment, sclerotial viability, and colonization by culturable fungi or bacteria were assessed with standard procedures. Greenhouse experiments were similarly conducted to evaluate endemic soil populations of Trichoderma spp. following soil exposure to VFAs and Trichoderma spp. populations assessed with standard soil dilution plating onto semi-selective medium. Sclerotial germination was generally reduced by soil exposure to acetic (35.1% germination) or n-butyric (21.9% germination) acids compared to water (74.3% germination) and HCl (62.7% germination). Germination was reduced as VFA concentration increased from 4 to 8 and 16 mmol/kg (39.5, 29.1, and 16.9%, respectively). In amended soils, there was no difference in sclerotial germination compared to non-amended soils, but in the greenhouse experiment there was a Trichoderma spp. population increase of over 300% in amended soil [3.4 × 106 colony forming units (CFU)/g soil] compared to the non-amended soil (9.6 × 105 CFU/g soil). Soil autoclaving had no effect on sclerotial germination at low VFA concentrations, but sclerotial germination was reduced at higher VFA concentrations compared to non-autoclaved soil. Our results suggest that VFAs contribute to sclerotial mortality in strongly acidic soil environments, and mortality is influenced by VFA components and environment. Antifungal activity is less for acetic acid than for n-butyric, and less in non-sterile soil environments more typical of field conditions than in sterile laboratory conditions.

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Section: Introductionmentioning

confidence: 91%

Mechanisms of Anaerobic Soil Disinfestation: Volatile Fatty Acids Reduce Viability of Athelia (Sclerotium) rolfsii Sclerotia in Acidic Soil Conditions and Have Limited Effects on Endemic Trichoderma spp.

Swilling

Shrestha

Ownley

et al. 2021

Front. Sustain. Food Syst.

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“…Sclerotia are responsible for the persistence and spread of the pathogen in stevia fields, making them a key target for disease control strategies [8]. ASD can reduce the viability of sclerotia by creating an anaerobic environment, physically damaging sclerotia, releasing toxic compounds, and producing organic acids that lower the soil pH and disrupt the internal metabolism of sclerotia [50,79].…”

Section: Effectiveness Of Integrating Asd and Fungicide Programs Unde...mentioning

confidence: 99%

Integrated Pathogen Management in Stevia Using Anaerobic Soil Disinfestation Combined with Different Fungicide Programs in USA, Mexico, and Paraguay

et al. 2023

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Stevia is a semi-perennial crop grown to obtain the diterpene glycosides in its leaves, which are processed to manufacture non-caloric sweeteners. Anaerobic soil disinfestation (ASD) and fungicide application were evaluated for the management of stevia stem rot (SSR) and Septoria leaf spot (SLS) in lab and field experiments. In 2019 and 2021, experiments using carbon sources for ASD were carried out in microplots at NCSU (Clayton, NC, USA). In 2020/21 and 2021/22 seasons, field experiments were conducted at CSAEGRO, Mexico (MX) and CEDIT, Paraguay (PY) using a 2 × 3 factorial design with two ASD treatments and three fungicide treatments. ASD treatments included soil amended with cornmeal (MX) or wheat bran (PY) at a rate of 20.2 Mg ha−1, molasses at 10.1 Mg ha−1, and non-amended controls. Fungicide applications included chemical (azoxystrobin), organic (pyroligneous acid, PA), and a non-treated control. ASD was effective in reducing sclerotia viability of Sclerotium rolfsii in laboratory assays (p < 0.0001) and microplot trials (p < 0.0001) in NC. During field trials, the viability of sclerotia was significantly reduced (p < 0.0001) in soils amended with cornmeal + molasses or wheat bran + molasses as carbon sources for ASD. While there was no significant effectiveness of ASD in reducing SLS in 2020 and 2021 or SSR in MX 2020 field trials (p = 0.83), it did exhibit efficacy on SSR in 2021 (p < 0.001). The application of fungicides was significantly effective in reducing SSR (p = 0.01) and SLS (p = 0.001), with azoxystrobin being the most consistent and PA not being statistically different from the control or azoxystrobin. The effects of ASD on fresh yield were inconsistent, exhibiting significant effects in Mexican fields in 2020 but not in 2021. During Paraguayan field trials, ASD only significantly interacted with fungicide applications in the dry yield in 2022. In the 2020/21 MX and 2020 PY field trials, fungicides were significantly effective in enhancing dry leaf yields, with azoxystrobin showing the highest consistency among treatments and PA variable control. In conclusion, utilizing ASD alongside organic fungicides can be a valuable tool for stevia farmers when the use of chemical fungicides is limited. Further research is required to enhance consistency and reduce the costs associated with these treatments under diverse edaphoclimatic conditions.

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“…The production of VFAs plays an important role in BSD. 29) In the GET system, the following bacteria related to VFA production were detected. The butyric acid-producing genus Coprococcus was present in all processes and especially increased at F_6.…”

Section: The Taxonomic Classifications Of the Sequences At The Genus ...mentioning

confidence: 99%

Biological soil disinfestation compatible with renewable energy production for sustainable agriculture

et al. 2022

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Biological soil disinfestation (BSD) is biotechnology to control soil-borne plant pathogens based on the anaerobic-reducing environment in soil and the functions of indigenous microbes. A new sustainable agricultural technology, the GET system, which produces and recovers methane as renewable energy from paddy fields, has a structure and principles similar to those of BSD technology. To confirm the potential of the GET system as BSD technology, the microbial community structures in the GET system were analyzed using next-generation sequencing. Thirty-four phyla were detected: 31 bacterial and 3 archaeal. Firmicutes dominated during the experimental period, which plays an important role in BSD functions such as organic decomposition, nitrate removal, and soil-borne pathogen elimination. The ability of the GET system to control soil-borne pathogens as well as produce renewable energy was demonstrated.

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Volatile fatty acid concentration, soil pH and soil texture during anaerobic soil conditions affect viability of Athelia (Sclerotium) rolfsii sclerotia

Cited by 8 publications

References 33 publications

Mechanisms of Anaerobic Soil Disinfestation: Volatile Fatty Acids Reduce Viability of Athelia (Sclerotium) rolfsii Sclerotia in Acidic Soil Conditions and Have Limited Effects on Endemic Trichoderma spp.

Mechanisms of Anaerobic Soil Disinfestation: Volatile Fatty Acids Reduce Viability of Athelia (Sclerotium) rolfsii Sclerotia in Acidic Soil Conditions and Have Limited Effects on Endemic Trichoderma spp.

Integrated Pathogen Management in Stevia Using Anaerobic Soil Disinfestation Combined with Different Fungicide Programs in USA, Mexico, and Paraguay

Biological soil disinfestation compatible with renewable energy production for sustainable agriculture

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