Developer of wheat crown rot resistance - Dr Phillip Davies

Material from his University program, funded by GRDC, has flowed back to all wheat breeders. This material is already impacting the variety development process with improved crown rot tolerance being combined with other features such as high yield, good quality and resistance to other diseases.

Crown rot (Fusarium pseudograminearum) is a stubble borne disease that commonly causes wheat and barley yield losses of $100s millions per annum with individual crop losses of over 50 per cent. While zero till farming has played a major role in reducing soil erosion and soil organic matter decline, crown rot has become a greater threat than in the cultivation era.

Crop rotations involving non host crops as chickpeas, canola, faba beans and grain sorghum are an important part of crown rot control strategy. However even with good rotations, particularly in drier years, infected crown rot stubble can remain a problem through a good rotation sequence. Therefore, the importance and urgency of breeding varieties with improved tolerance.

Developing improved tolerance to crown rot is no easy task. So far research has identified a multitude of genes that are responsible for improving crown rot tolerance. Inserting one single gene with tolerance into a variety (via breeding programs) on its own makes little improvement in control. Breeders need to identify and insert a multitude of genes to make any difference to a variety's ability to reduce yield loss when disease pressure is significant.

Fortunately, Dr Davies and colleagues from the University of Southern Queensland and CSIRO, have made significant progress in the past few years. Their best performing breeding lines averaged 36pc lower yield loss from crown rot than the current industry leading tolerant variety Suntop. This equates to a yield increase of 9pc above the current leading benchmark variety under disease pressure. In yield and dollar terms on a crop with potential yield of four tonne per hectare that represents an extra 0.36t/ha or over $100/ha extra profit. In part, this progress was also made possible by application of cutting-edge statistical analyses.

Philip Davies and colleagues have identified many crown rot tolerant genes and have matched them with closely linked molecular markers. These markers make it easier for researchers and breeders to incorporate into breeding lines and ultimately new varieties. They have combined or pyramided these resistance genes into single breeding lines in genetic backgrounds that make it easier for breeding programs to cross and produce new varieties with crown rot resistance and the suite of other traits required by Australian grain growers.

From a practical perspective, these lines with many crown rot tolerance genes have been made available to and accessed by commercial wheat breeding programs in both 2019 and 2020. Director of the Plant Breeding Institute, which includes the IA Watson Grains Research Centre at Narrabri, Professor Richard Trethowan, believes Dr Davies' program has been very successful with much yet to be achieved.

From internationally collected germplasm he is sure there remains many crown rot tolerance genes yet to be found and said the program was continuing to discover and incorporate more genes with a great deal of promising diversity yet to be exploited.

"Pyramiding the discovered genes into agronomically acceptable genetic backgrounds is a difficult and exacting task that requires a high level of skill and knowledge," he said.

He pointed out that improving crown rot tolerance would never be an easy task. Unlike the rust diseases, many genes of small but additive effect are responsible for improving tolerance. While new technologies may augment genetic progress, he is adamant that such improvements should be deployed in an integrated gene pyramiding scheme as the best way to improve crown rot tolerance in the longer-term.

Next week: New book highlights value of agriculture research