Arabinoxylan and pectin features differentiate maize inbred lines with contrasting Fusarium stalk rot resistance

Maize is susceptible to stalk rot caused by Fusarium graminearum, which reduces the forage quality and yield. This fungus spreads within the host, degrading pith cell walls and colonizing all other plant tissues. The aim of this research was to investigate genotypic differences in cell wall composition of two inbred lines (B73 and EA2024) with different resistance to Fusarium (susceptible and resistant respectively). We also compared the cell wall composition and structure of pith tissues between Fusarium-inoculated and non-inoculated plants. Cell wall analysis of non-inoculated plants showed no quantitative differences in major components between B73 and EA2024. However, quantitative variations between inbreds were detected in minor cell wall components including p-coumaric acid, ferulic acid, diferulic acids and mixed-linked β-glucans. Detailed structural analyses by subcritical water extraction of loosely-bound native polysaccharides indicated that EA2024 presented a pectin-enriched population, more mannans and callose, whereas the Fusarium-susceptible inbred B73 showed higher tightly-bound disubstituted xyloses in the arabinoxylan population. The infection scarcely affected the native composition of the cell wall in either of the two lines, while it did affect the degree of arabinoxylan substitution. The results obtained may contribute to a better understanding of the spread progression of Fusarium and the identification of cell wall markers to be used in the screening for new stalk-rot-resistant genotypes.