Arbuscular Mycorrhiza Inoculum Type Influences Phosphorus Subcellular Distribution in Shoots of Wheat Grown in Acidic Soil under Sustainble Agricultural Practices

Crop growth in acidic soils is generally limited by low soil fertility [low phosphorus (P) levels] and Al and Mn toxicity. Adequate P nutrition is normally supplied through soil P fertilizers that are obtained from mined phosphorite found mainly in Morocco. Unfortunately, the scarcity of this non-renewable mineral resource is already feared, which led some of the largest global fertilizer producers to cease exports¹. Arbuscular mycorrhizal fungi (AMF) are known to improve the host resistance to biotic and abiotic stress as well as water and nutrient acquisition, particularly P. When colonization is initiated from a pre-established intact extraradical mycelium (ERM), shoot P levels can increase almost 1.7-fold, depending on the plant species associated to ERM development (Developer)². In the present study, wheat (Triticum aestivum L.), one of the most widely produced cereal crops, was grown in acidic soil where intact ERM of AMF associated to native stress adapted Developers was previously grown. The non-mycotrophic Silene gallica L. (SIL), was compared to strongly mycotrophic Lolium rigidum L. (LOL) and Ornithopus compressus (ORN), whose role as ERM Developers have previously shown wheat growth promoting properties². After 3 weeks, wheat shoots P levels and subcellular redistribution were analysed through inductively coupled plasma mass spectrometry (ICP-MS)³.

Mycotrophic Developers established ERMs that promoted wheat shoot P accumulation (1.7 and 1.6-fold for LOL and ORN, respectively). Wheat P redistribution was determined after shoot sample fractionation through differential centrifugation. One fraction contained cell wall debris and metal granules (apoplastic fraction) and the other the organelles and vacuole contents (symplastic fraction). Shoots of wheat grown after SIL showed 40% of P at the apoplastic fraction while after LOL or ORN this proportion was approx. 50%.

Intact ERM from mycotrophic Developers adapted to acidic soils seems to influence crop growth by increasing P uptake and managing its subcellular distribution. This knowledge is important in the development of sustainable agricultural practices in the framework of net carbon zero-emission agriculture.

1. Campos, P. et al. Phosphorus Acquisition Efficiency Related to Root Traits: Is Mycorrhizal Symbiosis a Key Factor to Wheat and Barley Cropping? Front. Plant Sci. 9, 1–21 (2018).

2. Brito, I., Carvalho, M., Alho, L. & Goss, M. J. Managing arbuscular mycorrhizal fungi for bioprotection: Mn toxicity. Soil Biol. Biochem. 68, 78–84 (2014).

3. Faria, J. M. S. et al. Toxic levels of manganese in an acidic Cambisol alters antioxidant enzymes activity, element uptake and subcellular distribution in Triticum aestivum. Ecotoxicol. Environ. Saf. 193, 110355 (2020).