Synergy of Anaerobic Soil Disinfestation and Trichoderma spp. in Rhizoctonia Root Rot Suppression

Ram B Khadka,Sally A Miller

doi:10.3389/fsufs.2021.645736

Abstract

Potential synergy between anaerobic soil disinfestation (ASD) and Trichoderma spp. in suppression of Rhizoctonia root rot in radish was evaluated. A split-plot design with three replications was used; main plots were Trichoderma harzianum T22, Trichoderma asperellum NT25 and a non-Trichoderma control. Subplots were ASD carbon sources wheat bran, molasses, chicken manure, and mustard greens and two non-amended controls: anaerobic (covered and flooded) and aerobic (not covered or flooded). Carbon sources and Rhizoctonia solani inoculant were mixed with soil, placed in pots, and flooded, followed by drenching Trichoderma spore suspensions and sealing the pots in zip-lock bags. After 3 weeks, bags were removed, soil was aired for 1 week and radish “SSR-RR-27” was seeded. Rhizoctonia root rot severity and incidence were lowest in radish plants grown in ASD-treated soil amended with wheat bran, molasses, or mustard greens across all Trichoderma treatments. Disease severity was lower in radish plants treated with NT25 than with T22 or the non-Trichoderma control across all ASD treatments, and in radish grown in ASD-treated soil amended with wheat bran plus NT25 compared to ASD-wheat bran or NT25 alone. Rhizoctonia solani populations were significantly reduced by ASD treatment regardless of carbon source, while Trichoderma populations were not affected by ASD treatment with the exception of ASD-mustard greens. The interactions of either Trichoderma isolate and ASD with most carbon sources were additive, while T22 with ASD-molasses and NT25 with ASD–wheat bran interactions were synergistic in reducing disease severity. One interaction, T22 with ASD-chicken manure was antagonistic. Enhancement of ASD efficacy in suppressing soilborne diseases such as Rhizoctonia root rot by additional soil amendment with Trichoderma spp. during the process appears to be dependent on both Trichoderma isolate and ASD carbon source.

Highlights

Rhizoctonia solani is an important soilborne plant pathogen that causes diseases including root rot, crown rot, damping off, and foliar blight in numerous economically important plant species (AjayiOyetunde and Bradley, 2018)
Soil gravitational moisture percentage after Anaerobic soil disinfestation (ASD) treatment was not significantly different between the anaerobic control soils and soils amended with mustard greens, molasses, wheat bran or chicken manure, ranging from 24.9 to 25.9%
Paint loss was higher on IRIS tubes in ASD-treated soils amended with molasses, mustard greens, or wheat bran than in soil amended with chicken manure

Summary

Introduction

Rhizoctonia solani is an important soilborne plant pathogen that causes diseases including root rot, crown rot, damping off, and foliar blight in numerous economically important plant species (AjayiOyetunde and Bradley, 2018). Rhizoctonia solani frequently produces highly resilient sclerotia, has a wide host range, and is composed of diverse groups (anastomosis groups), making it difficult to Synergy Between ASD and Trichoderma manage (Ohkura et al, 2009) These diseases are challenging in vegetable production systems because of the succulent nature of the plants, lack of resistant cultivars, and limited fungicide efficacy. During decomposition of carbon sources, microbial activities increase and organic acids and volatile compounds are released, which results in significant changes in soil pH, metal ion availability, and microbial community composition (Momma et al, 2005; Momma, 2015) These changes and their interaction with other soil and environmental factors have negative impacts on plant pathogens in soil (van Agtmaal et al, 2015). Microbial community shifts in ASDtreated soils are driven by carbon source inputs (Mazzola et al, 2018; Testen and Miller, 2018)

Methods

Results

Conclusion