From pathogen to pathobiome: Rethinking helminthosporium leaf blight resistance in wheat

Helminthosporium leaf blight (HLB) of wheat is an increasingly important foliar disease complex prevalent in warm and humid production environments, caused by different combinations of multiple necrotrophic fungi, primarily Bipolaris sorokiniana, Pyrenophora tritici-repentis, and Alternaria triticina. Unlike classical single-pathogen systems, HLB represents a dynamic, multi-pathogen pathosystem characterized by frequent co-infection, overlapping symptoms and shared infection niches, complicating diagnosis and resistance breeding. This review synthesizes current knowledge on pathogen diversity, epidemiology, and host–pathogen interactions, with emphasis on necrotrophic effector–host sensitivity gene interactions operating under the inverse gene–for-gene model and their interplay with polygenic resistance mechanisms. Advances in QTL mapping, genome-wide association studies, and meta-QTL analyses are critically evaluated alongside emerging insights into effector diversity, virulence evolution, and genomic plasticity. Advances in molecular diagnostics, high-throughput phenotyping, and artificial intelligence-assisted disease detection are also discussed in the context of improving pathogen identification and trait resolution. Recent advances in pangenomics further provide a population-level perspective on pathogen and host diversity, highlighting the role of accessory genomes, effector variability and structural variation in shaping disease outcomes and resistance architecture. We propose a unified framework in which durable resistance is achieved by minimizing effector-triggered susceptibility while enhancing polygenic resistance. Future breeding strategies should integrate susceptibility gene management, pyramiding of stable resistance loci, and genomics-assisted selection to develop wheat cultivars with broad-spectrum, durable resistance against this multi-pathogen disease system.