Grainswest - Winter 2024

Winter 2024 Grains West 40 BATTLE THE BUNT Common bunt was also once prevalent on the Prairies. It has largely been brought under control by fungicide seed treatments and resistant cereal varieties. While it occasionally troubles organic farms, conventional operations almost never experience outbreaks. Ominously, when infection does set in, it can quickly devastate a crop and spores may live for multiple years in the soil. In Lethbridge, federal cereal pathologist Reem Aboukhaddour has operated a bunt nursery for seven years. The facility annually exposes hundreds of wheat genotypes to bunt. You must have a keen eye to spot bunt, she said. Aptly named, the infection is covered under a plant’s intact glumes, and symptoms become evident only after heading. They can remain undetected until harvest. The fungus grows systemically and replaces the potential kernels with masses of black teliospores that are contained under the glumes. Despite known controls, bunt remains a priority 1 disease for research scientists, along with Fusarium and all types of cereal rust. Aboukhaddour joked that bunt is treated like a second- class citizen in the disease world, but farmers and scientists best not ignore it. “Any little contamination of infected seed can ruin a big shipment of grain,” she said. While it diminishes yield, bunt infection causes significant quality losses, even at low levels. In Canada, grains contaminated with bunt spores at levels of 0.01 per cent or higher by weight are downgraded to animal feed. Livestock, however, do not like bunted grains. Grain handlers reject bunted grains for fear it will contaminate their systems. The infected grain is most easily identified by smell. Infected heads crushed between a person’s thumb and index finger release the unmistakable fishy odour of trimethylamine. The appearance of bunt, once fully developed, is striking. The spores, or bunt balls, are particularly hard to deal with if no seed treatment is applied, because the fungus is known to infect the emerging seedling below ground and grows alongside the plant’s maturing tips. The fungus prefers the cool six to 10 C range. Under cool temperatures the spores germinate, and slower plant development enables the fungus to reach the growing point of the plant prior to stem elongation. In warm soil, plants can escape the infection as they outgrow the fungus. Cereal pathologist Reem Aboukhaddour maintains the bunt nursery at the Agriculture and Agri-food Canada Lethbridge Research and Development Centre. Photos by George Clayton Photography. FEATURE