Wheat powdery mildew, caused by the obligate biotrophic fungus Blumeria graminis f. sp. tritici (Bgt), remains one of the most economically damaging foliar diseases of bread wheat worldwide. Regional assessments have quantified yield reductions of up to 35 percent in Russia, 62 percent in Brazil, and 40 percent in China, while studies across wheat-growing regions report losses of 13 to 34 percent under moderate infection, escalating to 50 to 100 percent in severe outbreaks. In the north-western Himalayas, documented losses have ranged from 8.7 to 41.3 percent. Because the severity of damage depends heavily on the phenological stage at which infection begins, early-season epidemics inflict the deepest cuts to both grain yield and quality. With fungicides carrying economic and environmental costs, genetically resistant cultivars are widely regarded as the most practical and sustainable defense, yet their long-term value is perpetually threatened by the pathogen’s remarkable capacity to adapt.
A new study published in Stress Biology has now provided one of the most detailed long-term pictures of how this adaptation unfolds. Researchers compared Bgt populations collected in the Northwestern Himalayan state of Himachal Pradesh, India, across two separate windows: 1994 to 1998 and 2015 to 2019. In total, 285 single-colony isolates were analyzed, comprising 215 historical isolates (155 conidial and 60 ascosporic) and 70 contemporary isolates (45 conidial and 25 ascosporic). Sampling spanned the major wheat-growing agro-climatic zones of the region, including the districts of Lahaul and Spiti, Kangra, Bilaspur, Una, Chamba, Shimla, and Hamirpur. Ascosporic isolates were derived from chasmothecia collected in the dry temperate zone, where the fungus completes its sexual cycle, while conidial isolates were established from actively sporulating field colonies.
Click here to see more...