Grainswest Tech 2021

Tech 2021 Grains West 48 Seed testingmay help defeat bacterial leaf streak Fight againstplantdiseaseexpands GRAIN SCIENCE NEWS BACTERIAL LEAF STREAK (BLS) IS a subtle intruder, but given the right con- ditions, it can cause significant yield loss and affect future crops in wheat and bar- ley. Most commonly transmitted through contaminated seed, the disease has the cereal industry pushing on all fronts to break the chain of transmission, starting with the development of an effective seed test to help farmers manage the risk and prevent it from spreading. Jeremy Boychyn is the Alberta Wheat and Barley Commissions’ agronomy research extension specialist. He first encountered BLS last summer. While at- tending industry events, southern Alber- ta farmers presented him with samples. “I was presented with plant material and asked what I thought it was. Two dif- ferent samples were brought to me, and it didn’t look like a common fungal patho- gen, it looked like leaf burn or something environmental,” said Boychyn. “The first sample I thought may have been impact- ed by hot weather. When the second sample came along, the symptoms were evident through the entire leaf area and looked like it impacted yield because it had taken away from the flag leaf, so I started to ask questions.” Boychyn turned to Michael Hard- ing, crop assurance lead with Alberta Agriculture and Forestry. Given his time in the field and as a research scientist in Brooks, Harding has more experience than most with bacterial leaf streak. “This is something that has been around for a long time, but it’s usually just a curiosity that shows up every once in a while and doesn’t do a lot of dam- age. Over the last 10 years that has been changing,” said Harding. In 2018, his team started seeing more outbreaks in fields around southern and central Alberta. Working with Jie Feng at the Alberta Plant Health Lab, they gathered infected tissue samples, isolated bacteria from the plant leaf and sent them to AAFC bacteriologist and taxono- mist James Tambong, who identified the pathogen as Xanthimonus translusens pv. undulosa. Preliminary trials to determine if there were any obvious differences in cultivar tolerance or resistance found that the pathogen was virulent on all ma- jor varieties of red spring wheat, barley, durum and winter wheat. HARD TO DIAGNOSE, RARELY APPEARS ALONE “It’s easy to misdiagnose BLS because it usually doesn’t just occur in isolation. There are often other fungal diseases that can sometimes make it challenging to know whether BLS is present and in a lot of cases BLS is present with oth- er fungal diseases as well,” said Maria Constanza Fleitas, a post-doctoral fellow working on BLS at the University of Saskatchewan. In the early stages of BLS, pale streaks run parallel to the veins of the leaf. These lesions will darken and take on a water-soaked appearance as the disease starts to develop. Under humid condi- tions, infected areas ooze bacteria seen as yellow thread-like masses that dry into thin shiny scales. Eventually the lesions grow together to cover large areas of the leaf, turning chlorotic (yellowing) and then the tissue becomes necrotic (dark and dead looking) and finally dies. At this stage, the disease can look very simi- lar to Septoria leaf blotch or tan spot. Damage to the leaf reduces the photo- synthetic leaf area of the plant, resulting in poor grain filling and reduced yield. The cereal industry is working to break the BLS chain of transmission pictured here.