Genotype-dependent effects of silicon and arbuscular mycorrhizal fungi on wheat phenolic metabolism

Silicon (Si) and arbuscular mycorrhizal fungi (AMF) have been widely recognized for enhancing plant tolerance to water deficit. However, the combined influence of these factors on the phenolic metabolism of wheat plants grown under water-limited conditions remains unclear. This study evaluated the effects of Si and AMF on the accumulation of phenolic compounds in two wheat genotypes differing in their tolerance to water deficit stress (Tukan-sensitive; Kiron-tolerant). A pot experiment was conducted under two irrigation regimes [90% of water holding capacity (WHC) and 40% WHC], two Si doses (0 or 1000 mg Si kg^-1 soil), and two AMF levels (-AMF, +AMF). Plants were grown under greenhouse conditions using a randomized factorial design with three replicates per treatment. Data were analyzed by analysis of variance (ANOVA), and treatment differences were determined by the LSD test (p ≤ 0.05). Plants were harvested at the tillering stage, and individual phenolic compounds were analyzed by HPLC–DAD–ESI-MS/MS. Accordingly, seven flavonoids [luteolin-hexoside-pentoside I, luteolin-hexoside-pentoside II, apigenin-pentoside-hexoside I, luteolin-hexoside-hexoside, apigenin pentoside-hexoside II, luteolin 7-(2″-pentosyl-4″ -O-hexosyl) hexoside, luteolin C-deoxihexosyl-O-hexoside, apigenin 8-C-rhamnoside-6-C-glucoside, and isoscoparin 2″-O-deoxyhexoside] were identified in shoots of both wheat genotypes, with apigenin and luteolin derivatives being predominant. In Tukan, higher concentrations of the identified phenolic compounds were detected in plants cultivated under water deficit than in well-watered plants. In contrast, Kiron showed no significant changes across irrigation regimes. Interestingly, the combined application of Si and AMF further increased phenolic accumulation in water-stressed Tukan but reduced phenolic levels in Kiron under the same conditions. Our results reveal that the synergistic action of Si and AMF can either stimulate or decrease phenolic accumulation depending on the wheat genotype. Moreover, these findings highlight the importance of cultivar-specific strategies when combining these beneficial approaches to improve drought tolerance. Acknowledgments: FONDECYT Projects N°1241718, N°11240738 and N°11240769, ANID, Chile.