Association of ZmLOX3 Status with Arbuscular Mycorrhizal Responses to Salt Stress in Maize

Abstract

Aims and Study Design: Arbuscular mycorrhizal fungi (AMF) can alter plant responses to salinity, but their effects depend on host genotype and may intersect with oxylipin signaling. We tested whether the maize 9-lipoxygenase gene ZmLOX3 and Rhizophagus irregularis DAOM 197198 were associated with contrasting responses in B73, its near-isogenic knockout line B73lox3-4, and the West African cultivar EV8728SR. Place and Duration of Study: The assay was conducted in the Laboratory of Phytopathology and Plant Biology at the Institut National Polytechnique Félix Houphouët-Boigny, Yamoussoukro, Côte d’Ivoire, from February to March 2024. Methodology: Non-inoculated and inoculated plants were exposed to 0, 68, or 102 mM NaCl. Data were analyzed using full salinity × inoculation × genotype models, followed by multiplicity-adjusted contrasts. Results: Salinity reduced growth, dry biomass, and tissue water status and increased Na⁺/K⁺ ratios. AMF responses varied by organ, genotype, and salinity: inoculation increased leaf biomass in several treatment combinations but reduced root biomass or relative water content in others. Three-way interactions were detected for leaf (P = 5.12 × 10⁻⁵), root (P = 7.74 × 10⁻⁷), and stem (P = 3.33 × 10⁻⁷) Na⁺/K⁺ ratios. Under severe salinity with AMF, the model-estimated root Na⁺/K⁺ ratio was 0.180 in B73, 0.0239 in B73lox3-4, and 0.0580 in EV8728SR. EV8728SR generally had the greatest absolute productivity, whereas relative stress indices sometimes favored B73 or B73lox3-4. Salinity also reduced mycorrhizal intensity, arbuscular abundance, and spore density. Conclusion: ZmLOX3 status was associated with AMF responses in root ion balance and water relations, but the knockout did not show universal salt tolerance. Selection should therefore combine absolute productivity, relative stability, ion homeostasis, and organ-specific AMF responses.