Genotype- and Experiment-dependent Biomass Stability of Maize Lines B73, EV8728SR, and W438 under Water Deficit and Rhizophagus irregularis Inoculation

Abstract

Background: Water deficit is a major constraint on maize growth, while the effects of arbuscular mycorrhizal fungi can vary with host genotype and experimental context. Aims: This study evaluated biomass stability and supporting physiological responses of B73, EV8728SR, and W438 under water deficit with or without Rhizophagus irregularis inoculation. Study Design: We compared B73, EV8728SR, and W438 in a genotype-complete assay at 100% and 10% soil water-holding capacity (WHC), with non-inoculated (NM) and AMF Rhizophagus irregularis (Ri) treatments, and independently evaluated B73 and EV8728SR across 100%, 50%, and 10% WHC. Place and Duration of Study: The experiments were conducted under controlled greenhouse conditions at Institut National Polytechnique Félix Houphouët-Boigny (INP-HB), Yamoussoukro, Côte d'Ivoire; the common assay ran from February to March 2024. Methodology: Total plant dry biomass was the primary endpoint. Positive outcomes were analysed with log-Gaussian factorial models and HC3 Type III tests; proportions were analysed using beta regression. Estimated marginal means were compared among all genotypes within each inoculation × water panel using Tukey adjustment, and biomass tolerance indices were estimated with 2,000 stratified bootstrap resamples. Results: In the common assay, biomass differed by genotype (F2,37 = 14.74, P < 0.0001) and water regime (F1,37 = 151.58, P < 0.0001), but not by genotype × water (P = 0.410) or genotype × inoculation × water (P = 0.614). EV8728SR had the greatest estimated severe-stress biomass (11.77 g NM; 15.16 g Ri) and the largest stress tolerance index under severe stress (STI; 0.523 NM; 0.659 Ri). In the independent gradient, however, B73 exceeded EV8728SR overall (F1,51 = 10.44, P = 0.0022), while water deficit remained the dominant effect (F2,51 = 43.23, P < 0.0001). Ion leakage showed a water-dependent three-way interaction (χ² = 12.05, P = 0.0024), whereas leaf area showed genotype × water and inoculation × water interactions after multiplicity control. Biomass provided no evidence of a general or genotype-specific Ri buffering effect. Conclusion: The contrasting genotype ranking between assays demonstrates that drought-tolerance claims should integrate absolute stress biomass, stability indices, and independent validation rather than relying on a single experiment or physiological proxy.