Characterization and effectiveness ofPhialophoraspp. isolated from a Montana take-all suppressive soil in controlling take-all disease of wheat

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Abstract
Selected fungi from a take-all suppressive wheat field in Montana were characterized morphologically and identified as Phialophora spp. Ribosomal DNA (rDNA) fragments from four Phialophora spp. and two known Gaeumannomyces isolates were amplified with polymerase chain reaction (PCR) using universal primers, cloned, and sequenced. Sequence comparison of the rDNA ITS regions revealed that these Phialophora isolates were not closely related to Gaeummanomyces sp. Alignment of the ITS sequences allowed the design of PCR primers that distinguished the Phialophora isolates from Gaeummanomyces sp. as well as Phialophora sp. related to Gaeummanomyces. Phialophora sp. 1-52 and Phialophora sp. 1-58 were tested alone and in combination for suppression of Gaeumannomyces graminis var. tritici in the field. When introduced on autoclaved canola seed, 1-52 proved to be an efficient biological control agent against wheat take-all disease in its original suppressive soil, as well as in a highly conducive soil. Isolate 1-58 did not provide protection in the suppressive soil, but did in two other soils, including the conducive soil. Protection was expressed as increased seedling dry weight, decreased root disease scores on mature plants, and increased grain yield as compared with the nonprotected check treatment in one of the two test years.