Mycorrhizal responsiveness to different phosphorus levels on the root colonization, agronomic efficiency and kernel quality of groundnut (Arachis hypogaea L.)

Arbuscular mycorrhizal fungi (AMF) are key components of sustainable agricultural systems, enhancing nutrient uptake and plant productivity, particularly in phosphorus (P)-deficient soils. This study investigated the interactive effects of three AMF species (Glomus mosseae, G. intraradices, and G. etunicatum), four P application levels (25, 50, 75, and 100 kg P₂O₅ha⁻¹), and two peanut cultivars (Goli and NC7) on root colonization, growth, yield, and seed quality under field conditions in the semi-arid Moghan plain, Iran. A factorial experiment was conducted in a randomized complete block design with three replications. Results revealed significant interactions between AMF species and P levels across all measured traits. Glomus mosseae achieved the highest root colonization (35.6% at 25 kg P ha⁻¹), but colonization declined with increasing P. Glomus etunicatum consistently enhanced plant height, chlorophyll index, and bush yield across P levels, with a notable 11% yield increase over the control at the lowest P rate. Glomus intraradices showed a positive, P-dependent response, maximizing oil content and yield at 100 kg P ha⁻¹. Notably, non-inoculated plants exhibited the highest tissue P concentration at 100 kg P ha⁻¹, indicating a down regulation of the mycorrhizal pathway under high P availability. G. etunicatum also reduced non-ripened seed numbers, promoting seed maturity. The findings demonstrate that AMF efficacy is species-and context-dependent. G. etunicatum is highly effective under low to moderate P fertility, making it ideal for low-input systems, while G. intraradices performs best under high P. An integrated nutrient management strategy moderate P fertilization (45-60 kg ha⁻¹) combined with targeted AMF inoculation can optimize peanut productivity, improve seed quality, and promote sustainable soil