Arbuscular mycorrhizal fungi inoculation improves iron deficiency in quince via alterations in host root phenolic compounds and expression of genes

Quince is known as an iron (Fe)-deficiency sensitive fruit tree, showing chlorosis symptoms when grown in calcareous soils. Arbuscular mycorrhizal (AM) fungi occurring widely in soils are able to increase plant growth and mineral uptake. An experiment was conducted to examine whether inoculation with AM fungi species would enhance Fe uptake in quince seedlings. The greenhouse experiment was arranged as a factorial experiment with two factors, including three AM fungi inoculation regimes (non-AM, Funneliformis mosseae, and Rhizophagus intraradices) and two Fe levels (50 mu M representing Fe-sufficiency and 5 mu M as Fe-deficiency). Fe-deficiency reduced biomass, chlorophyll concentration, and the chlorophyll fluorescence (F-v/F-m) ratio, but increased root colonization. Inoculation of seedlings with AM fungi, especially R. intraradices, led to significant enhancements in shoot and root dry weights, leaf chlorophyll content, and leaf F-v/F-m ratio in Fe-deficient quince when compared with the non-AM control. Under Fe-deficiency, AM-inoculated seedlings, compared to the non-AM plants, exhibited a higher root phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity and a greater root PAL1 gene expression. A similar result was noted for root phenolic compounds. AM colonization significantly promoted root and shoot Fe concentrations compared with the non-AM plants, in parallel with the increase in ferric chelate reductase (FCR, EC 1.16.1.7) enzyme activity and up-regulate FRO2 gene expression, under Fe-deficiency. These results suggest that enhancements in the phenolic compound content and, as well as PAL and FCR activities along with their co-regulation at transcriptional levels, could play key roles in AM-mediated mitigation of Fe stress in quince seedlings.