Genotype-dependent Biomass and Antioxidant Responses of Maize B73 9-Lipoxygenase Mutants and W438 to Water Deficit under Rhizophagus irregularis Inoculation

Abstract

Background: Water deficit substantially limits maize growth and productivity, while lipoxygenase-derived signalling and arbuscular mycorrhizal symbiosis may influence plant responses to water stress. However, the extent to which maize 9-lipoxygenase mutants differ in biomass and physiological responses to graded water deficit, and whether Rhizophagus irregularis modifies these responses in a genotype-dependent manner, remains unclear. Objective: This study aimed to evaluate genotype-dependent biomass responses of B73, B73lox3-4, B73lox12-1, and W438 under different water regimes; compare absolute and proportional biomass tolerance; determine whether Rhizophagus irregularis inoculation modifies water-deficit responses in a genotype-dependent manner; and assess whether tissue water content and antioxidant responses support the observed biomass patterns. Study Design: The study tested maize line B73; its near-isogenic 9-lipoxygenase mutants B73lox3-4 and B73lox12-1; and the comparator line W438 across 100%, 50%, and 10% soil water-holding capacity (WHC), with non-inoculated and Rhizophagus irregularis DAOM 197198 treatments. Place and Duration of Study: The experiment was conducted under controlled conditions at Institut National Polytechnique Félix Houphouët-Boigny (INP-HB), Yamoussoukro, Côte d'Ivoire, between February and March 2025. Methodology: Total plant dry biomass was the primary endpoint. The reanalysis used a three-factor model with HC3 heteroscedasticity-robust Type III tests, Tukey-adjusted genotype comparisons within every inoculation × water panel, and bootstrap confidence intervals for biomass-based tolerance indices. Results: Total biomass differed by genotype (F₃,₈₅ = 35.62, P < 0.0001), water regime (F₂,₈₅ = 128.34, P < 0.0001), and their interaction (F₆,₈₅ = 4.40, P = 0.000647). Under 10% WHC, model-estimated biomass was greatest for B73lox3-4 (13.76 g without inoculation and 16.75 g with R. irregularis); with inoculation, B73lox3-4 exceeded all three comparison genotypes by Tukey-adjusted grouping. Its severe-stress tolerance index was also highest (0.639 without inoculation and 0.800 with R. irregularis). B73lox12-1 showed comparatively strong proportional biomass retention without consistently matching the absolute biomass of B73lox3-4. Inoculation had no overall biomass effect (P = 0.689), and neither the inoculation × water interaction (P = 0.523) nor the genotype × inoculation × water interaction (P = 0.284) was significant. Antioxidant capacity was strongly genotype dependent but did not show a genotype × water interaction. Conclusion: These results identify B73lox3-4 as the strongest biomass-based performer in this seedling assay, while showing that the R. irregularis treatment did not confer a uniform or genotype-specific buffering effect. Overall, differences among maize genotypes were more important than fungal inoculation in determining seedling biomass under water deficit.