Arbuscular mycorrhizal fungus changes alfalfa (Medicago sativa) metabolites in response to leaf spot (Phoma medicaginis) infection, with subsequent effects on pea aphid (Acyrthosiphon pisum) behavior

Abstract

Plant disease occurs simultaneously with insect attack. Arbuscular mycorrhizal fungi (AMF) modify plant biotic stress response. Arbuscular mycorrhizal fungi and pathogens may modify plant volatile organic compound (VOC) production and insect behavior. Nevertheless, such effects are rarely studied, particularly for mesocosms where component organisms interact with each other.Plant-mediated effects of leaf pathogen (Phoma medicaginis) infection on aphid (Acyrthosiphon pisum) infestation, and role of AMF (Rhizophagus intraradices) in modifying these interactions were elucidated in a glasshouse experiment. We evaluated alfalfa disease occurrence, photosynthesis, phytohormones, trypsin inhibitor (TI) and total phenol response to pathogen and aphid attack, with or without AMF, and aphid behavior towards VOCs from AMF inoculated and non-mycorrhizal alfalfa, with or without pathogen infection.AM fungus enhanced alfalfa resistance to pathogen and aphid infestation. Plant biomass, root : shoot ratio, net photosynthetic rate, transpiration rate, stomatal conductance, salicylic acid, and TI were significantly increased in AM-inoculated alfalfa. Arbuscular mycorrhizal fungi and pathogen significantly changed alfalfa VOCs. Aphids preferred VOCs of AMinoculated and nonpathogen-infected to nonmycorrhizal and pathogen-infected alfalfa.We propose that AMF alter plant response to multiple biotic stresses in ways both beneficial and harmful to the plant host, providing a basis for strategies to manage pathogens and herbivore pests.

The Interaction between Arbuscular Mycorrhizal Fungi (AMF) and Grass Endophyte (Epichloë) on Host Plants: A Review

“…Grass endophytes confer prominent advantages to host plants, such as alkaloid production, induction of expression of anti-herbivore feeding genes, and alteration of volatile substance composition, which discourages feeding by herbivores [ 78 ]. The enhancement of plant resistance by AMF is undeniable [ 25 , 79 ]. However, studies on the interactions between grass endophytes and AMF and the resulting repulsion of herbivores and other biological stresses by the host plant remain scanty.…”

Colonization by orchid mycorrhizal fungi primes induced systemic resistance against a necrotrophic pathogen

“…We investigated the potential similarity in ISR between orchids and AM plants through comparative transcriptomics. Upon root colonization by mycorrhizal fungi, the host plants alter various metabolic pathways (Fontana et al ., 2009; Jacott et al ., 2017; Goddard et al ., 2021; Orine et al ., 2022; Li et al ., 2023); host plants increase their primary metabolic activity (nutrient uptake and remobilization) and temporarily lower the expression of defense-related genes (Schoenherr et al ., 2019; Jing et al ., 2022). In AM plants such as rice, genes associated with phosphate metabolism and phospholipid biosynthesis are upregulated, whereas non-phosphate lipids, which are later used in jasmonate biosynthesis, are downregulated (Campo and San Segundo, 2020).…”

Arbuscular mycorrhiza increases the facilitation between adult plant and seedling but root‐knot nematode inhibits it

“…Simultaneously, the benefit of sharing AM fungal hypha with neighboring plants will also increase with abiotic stress increase, and may be conducive to the growth of neighboring seedlings of invasive plants (Porter et al, 2020;Wang, Li, et al, 2023). AMF, as a kind of beneficial soil microorganism, can promote the resistance of host plants to biotic or abiotic stress when they form symbiosis with host plants (Li et al, 2023;Zeng et al, 2022). Therefore, we can predict that AM fungal symbiosis may ameliorate plant growth inhibition caused by biotic or abiotic stresses.…”