Differential stoichiometric responses of tolerant and susceptible sugarcane cultivars to silicon under drought and bacterial leaf scald

Abstract

Sugarcane production is frequently impacted by the simultaneous occurrence of water deficit and diseases such as leaf scald, caused by Xanthomonas albilineans . These stresses can disrupt water relations, nutrient balance, and biomass production. Silicon (Si) has been reported to mitigate both abiotic and biotic stresses, but its role in regulating C:N:P stoichiometry under combined stress conditions remains poorly understood. This study evaluated whether Si supplementation modulates leaf C:N:P stoichiometry, nutrient use efficiencies, and leaf dry mass production in two sugarcane cultivars differing in tolerance to X. albilineans . Water deficit and X. albilineans infection altered leaf nutrient balance and reduced nutrient use efficiency, with stronger effects in the susceptible cultivar SP78-4467. Silicon supplementation increased leaf Si concentration and modified C:N:P stoichiometric relationship in both cultivars, but the magnitude and direction of these responses depend on genotype and stress condition. In the tolerant cultivar SP80-3280, Si improved C and P accumulation, enhanced selected nutrient-use efficiencies, and partially mitigated the negative effects of combined water deficit and bacterial infection on leaf dry mass production. In contrast, the susceptible cultivar showed more limited and less consistent responses to Si under stress. Silicon can contribute to the regulation of leaf nutrient stoichiometry in sugarcane under combined abiotic and biotic stresses, but its effectiveness depends strongly on genotype and stress context. The results highlight the importance of integrating Si nutrition with genotype selection as a complementary strategy to improve sugarcane resilience under multiple-stress conditions.