Role of phenolics and lignin in cultivar resistance of wheat ears to Magnaporthe oryzae pathotype Triticum (MoT)

Wheat blast, caused by Magnaporthe oryzae pathotype Triticum (MoT), poses a serious threat to global wheat production. This study investigates the role of phenolic and lignin compounds in wheat ear tissues as potential biochemical markers of quantitative cultivar resistance to MoT. Two wheat cultivars— ‘Sumai 3’ (susceptible) and ‘Milan’ (resistant)—were inoculated at three distinct ear developmental stages: full ear emergence (GS 59), mid-flowering (GS 65), and end of flowering (GS 69). Blast symptoms appeared within 4–7 days post-inoculation. Sumai 3 exhibited rapid disease progression and high susceptibility to MoT at all stages, in contrast to Milan, which maintained resistant across all ear maturity stages. Quantification of fungal biomass revealed over 80-fold greater MoT accumulation in Sumai 3 ears compared to Milan. MoT colonization was predominantly observed in husks, followed by rachis and grains. Biochemical analyses demonstrated significantly elevated levels of cell wall-bound phenolics, and lignin in rachis tissues of Milan after infection. Histochemical studies further indicated early and localized accumulation of syringyl (S) lignin and induced cell wall thickening in Milan rachis, likely contributing to MoT resistance. These findings indicate the involvement of phenolic and lignin compounds in wheat basal resistance against MoT and offer novel insights for breeding blast resistant cultivars.