Natural suppression of take-all disease of wheat in Montana soils

Abstract

This research was initiated to determine whether soils suppressive to take-all of wheat caused by Gaeumannomyces graminis var. tritici (Ggt) occur in Montana, and to identify the organisms most likely involved in this suppression. From an initial screening of eight soils collected from different wheat growing areas of Montana, two were highly suppressive to take-all. Microbial characterization of these soils indicated that different mechanisms were involved in the suppression. In Larslan soil, mycoparasitism appeared to be the main mechanism. Two different fungi with exceptional ability to reduce the severity of take-all were isolated from this soil. One of these fungi could parasitize the hyphae of Ggt. Field tests with these fungi in Ggt infested soil showed increases of over 100% in both harvestable tillers and grain yield as compared to treatments without these two fungi. In tests with 48 different bacteria and 10 actinomycetes from Larslan soil, none were able to consistently reduce severity of take-all alone, or in mixtures. In Toston soil, antibiosis by actinomycetes and perhaps the involvement of Pseudomonas spp. in production of antibiotics and/or siderophores appeared to be the most likely mechanisms involved in take-all suppression. Increases in shoot dry weight over that in the Ggt infested control using mixtures of pseudomonads and actinomycetes ranged from 25% to 87%. Actinomycetes added individually or in mixtures to soil infested with Ggt consistently reduced the severity of the disease to a greater extent than did mixtures of Pseudomonas spp.

Gaeumannomyces graminis, the take‐all fungus and its relatives

“…A number of other bacterial species and a few fungal species have also been investigated (Dewan and Sivasithamparam, 1988; Duffy et al ., 1996; Kim et al ., 1997; Ross et al ., 2000; Rovira et al ., 1992; Ryder and Rovira, 1993; Sivasithamparam, 1998). Some of the fungi that have been found to be effective are closely related to the take‐all fungus, namely avirulent/hypovirulent isolates of G. graminis and Phialophora species (Andrade et al ., 1994; Duffy and Weller, 1995, 1996; Mathre et al ., 1998; Sivasithamparam, 1975; Wong et al ., 1996; Zriba et al ., 1999). The accumulated research on potential biological control agents for take‐all of wheat demonstrates that screening in vitro , and even in pot experiments, does not necessarily give a reliable indication of effectiveness in the field (Cook et al ., 1995; Elsherif and Grossmann, 1994).…”

Microbial Community Composition Affects Soil Fungistasis

“…duced that were no longer present after the microwaved, autoclaved-open, and autoclaved-closed treatments. For instance, actinomycetes, which are known for their production of antifungal compounds (3,5), may have been eliminated from these treatments. However, actinomycetes were not essential to the development of fungistasis, as prolonged incubation of microwaved and autoclaved-open treated soils also resulted in strong fungistasis despite no detection of actinomycetes in these soils.…”

Rhizosphere bacterial communities associated with disease suppressiveness stages of take‐all decline in wheat monoculture

“…In addition, Pseudomonas isolates producing antimicrobial compounds have been used successfully as wheat inoculant for the biological control of the pathogen Ggt (Thomashow & Weller, 1988;Keel et al, 1992;Raaijmakers & Weller, 1998). However, relatively little has been done so far to assess the role played by non-Pseudomonas bacterial populations in TAD (Andrade et al, 1994;McSpadden Gardener & Weller, 2001), and whether these bacteria can contribute to TAD remains to be established. Many non-Pseudomonas bacteria protect plants from soil-borne pathogenic fungi (Dunne et al, 1997;van Dijk & Nelson, 1998;Hebbar et al, 1998;Ryder et al, 1998;Bally & Elmerich, 2007;Raaijmakers et al, 2009) and some may be involved in soil disease suppressiveness (Andrade et al, 1994).…”

“…However, relatively little has been done so far to assess the role played by non-Pseudomonas bacterial populations in TAD (Andrade et al, 1994;McSpadden Gardener & Weller, 2001), and whether these bacteria can contribute to TAD remains to be established. Many non-Pseudomonas bacteria protect plants from soil-borne pathogenic fungi (Dunne et al, 1997;van Dijk & Nelson, 1998;Hebbar et al, 1998;Ryder et al, 1998;Bally & Elmerich, 2007;Raaijmakers et al, 2009) and some may be involved in soil disease suppressiveness (Andrade et al, 1994). Several studies have shown the potential of bacteria belonging to Actinobacteria and Bacillus to inhibit the growth of the pathogen Ggt (Kim et al, 1997;Coombs et al, 2004).…”