Mystery killer brought to book

Eradu patch at East Chapman WA.

TBR is easier to say than Thin Binucleate Rhizoctonia, and graingrowers need to get to know it.

TBR causes Eradu patch, stunted patches in narrow-leaf lupins, ill-thrift areas in barley and premature yellowing in wheat. In lupins, they're identical to the symptoms of Rhizoctonia bare patch and scientists have had a hard time bringing the culprit to book.

TBR defies the traditional isolating techniques used by scientists for definitive identification and they were unable to confirm its presence in soil samples taken across WA. That was before a GRDC-supported project began involving Gordon MacNish and Philip O'Brien of Murdoch University.

Using three types of DNA testing they lifted the identification of TBR rate from just 5 per cent of samples in 1997 to 94 per cent in 1999.

Discrepancies still existed, however, with only 34 per cent of the samples testing positive to all three tests.

One of the three tests, the "root plate" DNA test, which returned 83 per cent positive results, has been chosen as the most reliable.

The problem almost certainly exists everywhere in WA except the Esperance zone. Last year, 297 samples were collected at 10 km intervals along 3,050 km of roadside through the WA cereal belt. Lupin, barley or wheat crops were sampled and results show that the fungus was present in a third of the sites.

With a tool to detect and monitor the disease with a high rate of accuracy, future research will more effectively target treatment.

Program 2.6.3 Contact: Dr Gordon MacNish 08 9360 2784; Dr Philip O'Brien 08 9360 2785 email gmacnish@central.murdoch.edu.au or obrien@central.murdoch.edu.au