High‐throughput phenotyping reveals growth of Medicago truncatula is positively affected by arbuscular mycorrhizal fungi even at high soil phosphorus availability

Abstract

Arbuscular mycorrhizal fungi (AMF) may contribute to enhanced yield and nutrition of host plants for the purpose of sustainable agriculture. However, the growth response of the host plant to mycorrhizal colonization is generally only measured at harvest, and thus management decisions regarding AMF are made using only a single time point. This study highlights that AMF can provide growth benefits to the host plant over its life. Greater knowledge of how plants respond to AMF over time will improve understanding of how the association functions and ultimately lead to improved management decisions regarding AMF in an agricultural context. Summary • Colonization by arbuscular mycorrhizal fungi (AMF) can result in variable responses in the growth and mineral nutrition of host plants, and is highly dependent on soil nutrient condition; limited studies have addressed the effects of AMF on plant growth over time. The aim of this study was to investigate the AMF effects on plant growth over the life of the plant, and interactions with soil phosphorus (P) and zinc (Zn) availability. • We used a high-throughput shoot phenotyping system to examine the temporal growth responses to AMF and soil P and Zn availabilities in the pasture legume Medicago truncatula. Plants were either inoculated with Rhizophagus irregularis or mock-inoculated, and were examined under two soil P and five soil Zn availability treatments. Plants were then destructively harvested to obtain final biomass and shoot nutrition data. • The growth of M. truncatula plants over time responded very differently to AMF depending on the soil P availability. At low P, projected shoot area and absolute growth rate (AGR) became increasingly greater in the mycorrhizal plants over the course of the experiment. At high P, there was a positive growth response to AMF until approximately 40 days after planting, after which the AGR of the 2 | TRAN eT Al.

Arbuscular Mycorrhizal Symbiosis Differentially Affects the Nutritional Status of Two Durum Wheat Genotypes under Drought Conditions

“…In particular, mycorrhized plants displayed a decreasing S index (meaning a better sulfur nutrient status of the plants) under well-watered and water stressed conditions, indicating that AMF positively impacts sulfur homeostasis in Svevo and Etrusco. Our results agreed with the beneficial role of AM symbiosis in the nutrient homeostasis of plants [ 40 , 67 , 100 , 101 ]. Notably, the Etrusco cultivar displayed higher S index values under all conditions considered, suggesting that sulfur homeostasis is differentially affected in Etrusco with respect to the Svevo cultivar.…”

Enhancement of sorghum grain yield and nutrition: A role for arbuscular mycorrhizal fungi regardless of soil phosphorus availability

“…This AM-mediated growth depression early on may be due to a carbon (C) drain on the plant-a cost to establish the AM association, before there was activity of the mycorrhizal pathway(s) of nutrient uptake to compensate the drawdown. Early effects of AM colonisation on aboveground biomass have been demonstrated previously using this HTP system in other plant species, such as Medicago truncatula, tomato and barley (Tran, Cavagnaro, Jewell, et al, 2021;Watts-Williams, Jewell, et al, 2019). The shoot growth depressions observed in response to AM colonisation continued until 50-55 DAP (depending on the genotype), before the response to AM inoculation became neutral.…”

Role of soil biota in grassland restorations in high nutrient soils

“…Thus, in restoration sites with high nutrient availability, we might expect the role of AM fungi to be diminished. Yet, several studies provide a counterpoint by showing some plant species benefit from AM fungi in high nutrient soils (Kothari et al 1991; Chu et al 2020; Tran et al 2020), even when grown in the field with P fertilizer (Peña Venegas et al 2021). This benefit may reflect non‐nutritional benefits of AM fungi to plants (Delavaux et al 2017) or variable nutrient demands of different plant species.…”