BRACHIARIA AS AN ALTERNATIVE HOST OF MAGNAPORTHE ORYZAE: EPIDEMIOLOGICAL IMPLICATIONS FOR WHEAT BLAST

Wheat blast, caused by Magnaporthe oryzae pathotype Triticum (MoT), is a major constraint to wheat production in tropical and subtropical regions. Although traditionally regarded as a crop-specific disease, increasing evidence indicates that wheat blast is driven by multihost epidemiological processes operating at the landscape scale. In this context, forage grasses of the genus Urochloa (syn. Brachiaria) have emerged as epidemiologically relevant alternative hosts. This review synthesizes experimental, molecular, and field-based evidence demonstrating the susceptibility of Urochloa species to M. oryzae, including MoT, and discusses the implications for wheat blast epidemiology. Studies consistently show that Urochloa spp. can sustain pathogen populations between wheat cropping seasons, acting as reservoirs of primary inoculum and reinforcing the “green bridge” concept. Variation in cultivar susceptibility further indicates that forage species and cultivar choice may significantly influence disease risk in wheat-growing regions, particularly under crop–livestock integration systems. Moreover, the coexistence of multiple grass hosts favors pathogen persistence, gene flow, and selection of aggressive genotypes, contributing to the long-term stability of wheat blast epidemics. Collectively, the evidence supports a paradigm shift from crop-centered disease management to landscape-level approaches that explicitly account for alternative hosts. Incorporating forage grasses into epidemiological models and management strategies is essential to reduce inoculum carryover and improve the sustainability of wheat production in tropical agroecosystems.