Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon Effect of polyamines and nitric oxide in Piriformospora indica-induced resistance and basal immunity of wheat against Fusarium pseudograminearum Saeedeh Dehghanpour-Farashah, Parissa Taheri ⁎ , Mahrokh Falahati-Rastegar Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box: 91775-1163, Mashhad, Iran ARTICLE INFO Keywords: Crown rot Spermidine Sodium nitroprusside Guaiacol peroxidase Catalase Callose ABSTRACT Fusarium crown rot of wheat is an important disease worldwide. The lack of commercial resistant cultivars and effective fungicides against Fusarium, make controlling the disease very difficult. Biocontrol can be an en- vironmentally friendly method to reduce the progress of various diseases caused by Fusarium species. Piriformospora indica is a root endophytic fungus with a wide range of host plants, which increases their growth and tolerance to biotic and abiotic stresses. In this study, capability of P. indica to protect wheat seedlings against Fusarium pseudograminearum, causing crown rot, was investigated and the role of polyamines (PAs) and nitric oxide (NO) as signal molecules involved in plant defense pathways in induced resistance by this endophytic fungus was evaluated in this pathosystem for the first time. Our results showed that P. indica did not have any antagonistic effect on F. pseudograminearum in vitro but considerably reduced the disease progress on wheat seedlings and detached leaves. Also, P. indica increased plant growth parameters compared to the controls in greenhouse. Application of spermidine (Spd; a polyamine) and sodium nitroprusside (SNP; a NO donor) revealed that PAs and NO had significant effect on basal immunity and P. indica-induced resistance (Pi-IR) via elevation of H 2 O 2 levels, guaiacol peroxidase (GPX) and catalase (CAT) activity, callose deposition, relative water content (RWC) and membrane stability index (MSI) compared to the plants only inoculated with F. pseudograminearum and uninoculated controls. In addition, our data demonstrated that PAs and NO synergistically enhanced basal resistance and Pi-IR against Fusarium crown rot in wheat plants. 1. Introduction Crown rot is an important disease on cereals worldwide. Fusarium species cause browning and rotting of the subcrown internodes and crowns of wheat, which reduce the grain yield (Zhang et al., 2015). This disease have been reported from different geographical regions of the world such as Asia (Braun et al., 2004; Besharati Fard et al., 2017), North Africa (Nicol et al., 2004), South Africa (Lamprecht et al., 2006), Europe (Pettitt and Parry, 2001), Australia (Burgess et al., 2001), North America (Smiley et al., 2005) and South America (Burgess et al., 2001). Biological control is one of the environmentally safe methods for controlling phytopathogens. There are only a few studies on biocontrol of Fusarium spp. causing wheat crown rot and Piriformospora indica is considered as a promising agent in the biocontrol of this disease. The effect of P. indica was evaluated against F. graminearum and F. cul- morum, causing wheat crown rot by Rabiey et al. (2015), but the me- chanisms of plant protection by this beneficial endophytic fungus were not investigated, so far. To our knowledge, this is the first detailed study on the effect of P. indica on wheat - F. pseudograminearum pathosystem. P. indica (Pi) is a cultivable Basidiomycete belonging to Sebacinales, which colonizes the roots of a wide range of plants and increases their growth, biomass, seed production, tolerance to abiotic stresses and re- sistance against microbial pathogens (Oelmüller et al., 2009; Qiang et al., 2012; Sun et al., 2014; Saddique et al., 2018). Information on the mechanisms of P. indica interaction with plants are scarce, yet. Various studies demonstrated that P. indica activates different mechanisms in the host plants, including growth promotion via higher production of phytohormones such as auxins and cytokinins by P. indica (Hilbert et al., 2013), systemic resistance against the biotrophic leaf pathogens such as Blumeria graminis f. sp. hordei and Golovinomyces orontii by af- fecting levels of jasmonic acid (JA), ethylene, abscisic acid (ABA) and salicylic acid (SA) (Molitor et al., 2011), elevating intracellular calcium and stimulating ROS production in Arabidopsis roots (Vadassery and Oelmueller, 2009; Vahabi et al., 2015), increasing antioxidative re- sponses in barley, maize and rice against F. culmorum, F. verticilloides and R. solani (Harrach et al., 2013; Nassimi and Taheri, 2017). Polyamines (PAs), mainly diamine putrescine (put), triamine sper- midine (spd) and tetraamine spermine (spm) are aliphatic, polycationic https://doi.org/10.1016/j.biocontrol.2019.104006 Received 7 November 2018; Received in revised form 8 June 2019; Accepted 10 June 2019 ⁎ Corresponding author. E-mail address: p-taheri@um.ac.ir (P. Taheri). Biological Control 136 (2019) 104006 Available online 11 June 2019 1049-9644/ © 2019 Elsevier Inc. All rights reserved. T