Quantitative PCR to detect Gaeumannomyces graminis var. tritici in symptomatic and non-symptomatic wheat roots

The soil-borne ascomycete Gaeumannomyces graminis var. tritici causes take-all of wheat (Triticum aestivum). Between host crops, G. graminis var. tritici survives saprophytically on crop debris and by infecting susceptible grass weeds or cereal volunteers. Invasion of roots in the following wheat crop results in reduced grain yield and quality. Take-all is commonly assessed in the field by visual inspection. Molecular-based methods are also available to detect G. graminis var. tritici, including a quantitative PCR (qPCR) assay that indirectly measures the amount of pathogen DNA in environmental samples. The qPCR is used as part of a commercial tool (known as PreDicta B (TM)) to predict the risks of take-all in wheat crops prior to planting, which are dependent on the amount of Gaeumannomyces inoculum in field soils. Unfortunately, the costs associated with the PreDicta B (TM) test can be prohibitive to its use. As a result, in this study, an alternative qPCR assay was developed to measure directly the DNA of G. graminis var. tritici. The assay was shown to detect DNA of G. graminis var. tritici in both symptomatic and non-symptomatic wheat roots, with an increase in the amount of DNA detected having a strong relationship with an increase in take-all symptoms.