Enhanced field control of wheat take‐all using cold tolerant isolates of Gaeumannomyces graminis var. graminis and Phialophora sp. (lobed hyphopodia)

Abstract

Cold tolerant isolates of Gaeumannomyces graminis var. graminis (Ggg) and Phialophora sp. (lobed hyphopodia), which produced at least comparable growth rates at 58C to those of pathogenic G. graminis var. tritici (Ggt), were shown to control take-all disease in wheat effectively in 2 years of field experiments in New South Wales, Australia. The addition of oat inoculum of these fungi at the rate of 60 kg/ha to the seeding furrow significantly (P 4 0 . 05) reduced disease and increased grain yields by 33-45% compared to the Ggt alone treatment. The use of 30 kg/ha of oat inoculum also significantly (P 4 0 . 05) reduced disease and increased grain yields by 21-44%. These high levels of take-all control were obtained consistently from four field experiments on three different soil types with different pHs. A treatment inoculated with Ggg alone showed no disease symptoms and produced grain yields similar to that of untreated wheat. This fungus is, therefore, non-pathogenic to wheat. At high rates of inoculation of Ggg and Phialophora sp. (lobed hyphopodia), 65-80% of tillering wheat plants (GS 32) had root systems colonized by these fungi. In contrast, two Pseudomonas spp. and an isolate each of Ggg and Phialophora sp. (lobed hyphopodia), which did not grow at 58C, were ineffective in controlling take-all. Take-all assessments during heading (GS 61-83) were highly correlated (R 2 =0 . 6047, P40 . 0005) with the relative yield increase or decrease of inoculated treatments compared to the Ggt alone treatment. The use of a Ggg isolate (90/3B) and a Phialophora sp. (lobed hyphopodia) isolate (KY) for take-all control has been patented. These fungi are being developed for commercial use.

Isolation and Characterization of a Cold-Tolerant Strain of Fusarium proliferatum, a Biocontrol Agent of Grape Downy Mildew

“…Thus, a desired phenotype was obtained in a positive selection protocol, although the genes conferring this desirable trait are not yet available (in this or any other organism). In fact, even though significant advances have been made in analyzing the molecular basis for cold tolerance in plants (19), there are only a few reports on cold tolerance in fungi (2,10,17,36,40). Furthermore, introduction of foreign DNA was not required, a factor that may prove to be crucial at a time when public concerns regarding the use of transgenic organisms prevail (4,18,21).…”

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).…”

The potential of non‐pathogenic Gaeumannomyces spp., occurring naturally or introduced into wheat crops or preceding crops, for controlling take‐all in wheat

“…Limited, partial control has been achieved in the field in other parts of Europe, where control was most effective where artificial inoculum of Ggt was also applied (Martyniuk & Myśków, 1984; Speakman, 1984). It is possible that carefully selected strains (Wong et al , 1996) may perform more effectively. In UK arable soils, which are microbiologically complex and are probably microbiologically well buffered, it may be expected that applied biocontrol agents will have difficulty becoming established and surviving in competition with the natural microbiota (Hornby et al , 1998).…”

“…graminis ( Ggg ), also has the potential to suppress take‐all, and has the presumed advantage of being faster growing than G. cylindrosporus (Walker, 1981). Strains of Ggg tested in Australia have been proposed as biocontrol agents of take‐all (Wong et al , 1996). Little is known of the population dynamics of Ggg in wheat fields, however.…”