Spot blotch pathogens revisited: taxonomic insights and resistance strategies in wheat—a mini review

Spot blotch, caused by Bipolaris sorokiniana (teleomorph Cochliobolus sativus), is one of the most destructive fungal diseases of wheat (Triticum aestivum L.) posing a serious threat to global food security, particularly in the warm and humid agro-ecologies of South Asia. The disease substantially reduces photosynthetic efficiency, biomass accumulation, and grain yield, with losses reaching 40–44% in India and even higher in susceptible cultivars under favorable environmental conditions. This review consolidates historical and contemporary knowledge on the pathogen taxonomy, host range, morphology, molecular phylogeny, phytotoxicity, and economic importance. Major taxonomic revisions have reclassified the pathogen from Helminthosporium to Drechslera and finally to Bipolaris, with molecular phylogenetic analyses using ITS, LSU, EF1-α and GPDH loci providing improved clarity within the Bipolaris, Cochliobolus and Curvularia complex, despite continued confusion due to dual nomenclature. Pathogenicity is closely associated with the production of phytotoxins such as helminthosporol, sorokinianin and bipolaroxin, along with considerable genetic and physiological variability among populations. Resistance breeding remains a key management strategy, with several quantitative trait loci (QTLs) and resistance genes (sb1, sd2, sb3, sb4 and Lr34/Lr46) identified from cultivated and wild germplasm. However, the polygenic nature of resistance and high pathogen diversity limit the durability of single resistance sources. Therefore, integrated disease management combining resistant cultivars, cultural practices, and judicious fungicide use is essential. Future efforts should emphasize taxonomic resolution, functional genomics, and the integration of molecular breeding and gene-editing tools to achieve durable resistance and sustainable wheat production under changing climatic conditions.