Growth and Nutritional Enhancement of Lisianthus (Eustoma grandiflorum (Raf.) Shinn.) via Dual AMF Inoculation Under Phosphorus Regimes

The arbuscular mycorrhizal fungi (AMF) form symbiotic, mutually beneficial relationships in the rhizosphere, and modulate phosphorus’ (P) availability to regulate plant growth, nutrient uptake, and quality. However, their roles in cut-flower species remain poorly understood. The aim of this study was to evaluate the effects of single and dual inoculation with Glomus intraradices and G. mosseae on Lisianthus (Eustoma grandiflorum) grown under three P levels (10, 20, and 40 mg kg−1) in greenhouse conditions. Under intermediate P, dual-inoculated plants exhibited the greatest above-ground vigor, with increases in stem length (+31%), dry shoot weight (+67%), and highest shoot P (+54%) and N (+23%) content, compared with non-inoculated controls. Under low P, dual inoculation maximized dry root weight (+63%) and mycorrhizal colonization, whereas AMF effects diminished at high P. Principal component analysis showed that there were distinct mycorrhizal interactions (PCA2, 20.3% variance) and a close integration between vegetative growth and nutrient accumulation (PCA1, 54.3% variance). For the first time, this study demonstrates that Lisianthus exhibits a strong response to dual AMF inoculation, offering a novel strategy to enhance growth, nutrition, and ornamental quality when P fertilization is optimized. By reducing chemical fertilizer use, this dual AMF–P management offers a sustainable framework for high-quality cut-flower production.