Two Cultivars of Peanut (Arachis hypogaea) Show Different Responses to Iron Deficiency

Background: Peanut is susceptible to iron (Fe) deficiency, particularly in calcareous soils. However, comparative studies on the adaptive mechanisms of different peanut cultivars to Fe deficiency remain limited. This study aimed to investigate the physiological and molecular responses of two distinct peanut cultivars to Fe deprivation and to identify the key traits contributing to differential Fe efficiency. Methods: Two peanut cultivars, LH11 and YZ9102, were cultivated under Fe-sufficient and Fe-deficient conditions, using both hydroponic and pot-based soil culture systems. Multiple parameters were assessed, including visual symptomology, biomass, tissue Fe concentration, active Fe in leaves, chlorophyll (Chl) content (SPAD value), net photosynthetic rate (Pn), Chl fluorescence (Fv/Fm), rhizosphere pH, root ferric chelate reductase (FCR) activity, and the relative expression of two Fe-acquisition-related genes (AhIRT1 and AhFRO1) via qRT-PCR. Results: Cultivar YZ9102 exhibited more severe Fe deficiency chlorosis symptoms, which also appeared earlier than in LH11, under both cultivation systems. Under Fe deficiency, YZ9102 showed significantly lower Chl content, Pn, and Fv/Fm compared to LH11. In contrast, LH11 demonstrated a greater capacity for rhizosphere acidification and maintained significantly higher root FCR activity under Fe-limited conditions. Gene expression analysis revealed that Fe deficiency induced the up-regulation of AhIRT1 and AhFRO1 in the roots of LH11, while their transcript levels were suppressed or unchanged in YZ9102. Conclusions: The peanut cultivar LH11 possesses superior tolerance to Fe deficiency compared to YZ9102. This enhanced tolerance is attributed to a synergistic combination of traits: the maintenance of photosynthetic performance, efficient rhizosphere acidification, heightened root Fe³⁺ reduction capacity, and the positive transcriptional regulation of key Fe uptake genes. These findings provide crucial insights for the selection and breeding of Fe-efficient peanut varieties for cultivation in Fe-deficient environments.