Prediction of take-all disease risk in field soils using a rapid and quantitative DNA soil assay

A rapid, routine DNA-based assay to quantify Gaeumannomyces graminis var. t ritici (Ggt), the causal agent of take-all disease of cereals, has been dev eloped and used for the prediction of take-all in a wide range of field soi ls. Based on the correlation of the DNA-based assay and a soil bioassay, th e risk of disease development can be estimated. Ggt DNA levels of < 30 pg, 30-50 pg and > 50 pg in 0.1 g soil organic matter correspond to low, modera te and high levels of the disease, respectively. Limitations in the predict ion of take-all, including sampling requirements to obtain representative s oil samples from fields and increasing the sensitivity and the accuracy of the DNA assay, are described. The main advantage in using the DNA-based ass ay, in estimating the amount of Ggt inoculum in soil, is that the levels of Ggt in soil samples can be assessed rapidly and accurately. Farmers can no w have soil samples assessed before sowing. The DNA result can be used to p redict the potential yield loss and determine the most appropriate manageme nt options using decision support software that is currently available. Thi s DNA technology is currently being used commercially to detect and predict take-all.