ENHANCED FIELD CONTROL OF WHEAT TAKE-ALL USING COLD TOLERANT ISOLATESOF GAEUMANNOMYCES-GRAMINIS VAR GRAMINIS AND PHIALOPHORA SP (LOBED HYPHOPODIA)

Cold tolerant isolates of Gaeumannomyces graminis var. graminis (Ggg) and Phialophora sp. (lobed hyphopodia), which produced at least compar able growth rates at 5 degrees C to those of pathogenic G. graminis va r. tritici (Ggt), were shown to control take-all disease in wheat effe ctively 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 t o the seeding furrow significantly (P less than or equal to 0.05) redu ced disease and increased grain yields by 33-45% compared to the Ggt a lone treatment. The use of 30 kg/ha of oat inoculum also significantly (P less than or equal to 0.05) reduced disease and increased grain yi elds by 21-44%. These high levels of take-all control were obtained co nsistently from four field experiments on three different soil types w ith different pHs. A treatment inoculated with Ggg alone showed no dis ease symptoms and produced grain yields similar to that of untreated w heat. This fungus is, therefore, non-pathogenic to wheat. At high rate s 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 a nd Phialophora sp. (lobed hyphopodia), which did not grow al 5 degrees C, were ineffective in controlling take-all. Take-all assessments dur ing heading (GS 61-83) were highly correlated (R(2)=0.6047, P less tha n or equal to 0.0005) 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 de veloped for commercial use.