Phoma stem canker, a major threat to global oilseed rape yields, is becoming harder to control due to genetic changes in fungal populations that reduce fungicide effectiveness. This raises urgent concerns about the sustainability of current disease management in European agriculture.
The post New Resistance Pathway to Azoles Found in Phoma Stem Canker Fungus appeared first on Seed World.
Phoma stem canker, a serious crop disease that threatens oilseed rape yields worldwide, may be becoming more difficult to control following the discovery of genetic changes in fungal populations that reduce the efficacy of commonly used fungicides. These findings raise urgent concerns about the long-term sustainability of current disease management practices in European agriculture.
The disease is caused by two closely related fungal pathogens: Plenodomus lingam and P. biglobosus. For decades, farmers have relied on azole fungicides to manage Phoma, but reduced sensitivity in P. lingampopulations in Western Europe was first reported in 2024. Now, new research published in Pest Management Science confirms, for the first time globally, that P. biglobosus is also exhibiting decreased sensitivity to azoles.
In contrast to P. lingam, the reduced sensitivity in P. biglobosus has been traced to a single mutation in the CYP51 gene — the known target of azole fungicides. This marks the first documented case of target-site resistance to azoles in any Phoma pathogen, according to a press release.
“The mutation found in P. biglobosus is linked to a 7-fold decrease in sensitivity to the azoles tested. On its own, this is unlikely to contribute to Phoma disease control failure, but it is a worrying step in the wrong direction” said Rothamsted’s Dr Kevin King who led the research. “Ongoing evolution of the pathogens may in future lead to azole resistance in the field and subsequent disease control failures”. As oilseed rape remains a vital crop for food and biofuel production in the UK and beyond, the emergence of such fungicide resistance could have serious food and energy security implications.
The newly identified mutation has so far been confirmed in P. biglobosus populations from Poland and the UK. Its presence may help explain recent reports of this strain emerging as a more prominent contributor to Phoma stem canker in Europe. Ongoing surveillance is now essential to determine the distribution and prevalence of the mutation across European P. biglobosus populations, as well as to assess whether similar mutations may be developing in P. lingam. Additional research is also needed to explore strategies that can slow the development of resistance driven by the widespread use of azole fungicides.
“Research into integrated pest management strategies — including crop rotation, resistant cultivars, and reduced reliance on fungicides — will also be important to safeguard future yields” explains Rothamsted’s Professor Jon West, a co-author on the study.
This work was a collaborative project between Rothamsted Research and the Polish Institute of Genetics, with work at Rothamsted supported by the Growing Health and Resilient Farming Futures strategic programmes.
The post New Resistance Pathway to Azoles Found in Phoma Stem Canker Fungus appeared first on Seed World.