Quinoa (Chenopodium quinoa Willd.) is a strategic crop for climate-smart agriculture in the Andes, yet yield gains are constrained by soil degradation and low-input systems. We tested whether synergistic bioinoculation with a plant growth-promoting rhizobacterium (Azospirillum brasilense) and an arbuscular mycorrhizal fungus (Glomus iranicum var. tenuihypharum) enhances root function and grain productivity under field conditions. A split-plot RCBD was conducted in Ayacucho, Peru (2735 m a.s.l.) using four cultivars, Blanca de Junín (BJ), INIA 441 Señor del Huerto (SH), INIA 415 Pasankalla (RP) and INIA 420 Negra Collana (NC) and four treatments: uninoculated control, Azospirillum, Glomus and co-inoculation. Vegetative, root and yield traits were quantified; ANOVA, Tukey/Dunnett contrasts, correlations and PCA were applied. Co-inoculation consistently outperformed single inoculants, increasing root diameter, length, branching, dry weight and volume dry weight, while also enlarging panicle dimensions and raising grain weight per panicle and thousand-seed weight. Grain yield reached 4.94 ± 0.59 t ha⁻¹ under co-inoculation, almost triple that of the control (1.71 ± 0.28 t ha⁻¹) and about 1.5 times higher than single inoculations. Genotypic effects were pronounced; BJ and SH combined superior root biomass with higher yield, RP maximized grain size and hectoliter weight, whereas NC responded weakly. Significant genotype × treatment interactions indicated cultivar-dependent microbiome benefits. Correlation and PCA linked root biomass and stem/panicle architecture to yield formation, positioning co-inoculation along trait vectors associated with belowground vigor and productivity. These results demonstrate a robust microbial synergy that translates root gains into yield, supporting co-inoculation as a scalable, low-input strategy for sustainable intensification of quinoa in highland agroecosystems.

Purple corn (Zea mays L.), a traditional Andean crop valued for its high anthocyanin content and increasing relevance in the nutraceutical industry. However, its production is challenged by envirmental stress and the overuse of chemical fertilizers in Andean ecosystems. This study evaluated the effects of co-inoculation with Azospirillum brasilense (a plant growth-promoting rhizobacterium, PGPR) and Glomus iranicum var. tenuihypharum (an arbuscular mycorrhizal fungus, AMF) on growth and yield performance in five purple corn genotypes under highland field conditions in Ayacucho,Peru. A randomized complete block design with three replications was implemented across two locations to compare a control (no inoculation) with individual and combined microbial treatments. Results showed that combined inoculation significantly improved vegetive parameters, ear and yield-related traits in both locations, with increases of up to 60.8% in grain yield compared to the control. Statistically significant differences were observed among treatments and genotypes (Tukey, p < 0.05), with the Canaán location showing the highest overall performance between control and combined microbial treatments. These findings support the potential of PGPR-AMF consortia to sustainably enhance purple corn productivity and resilience, offering a viable alternative to reduce chemical inputs in Andean agriculture.