Chapter

Impact of Arbuscular Mycorrhizal Symbiosis on Plant Response to Biotic Stress: The Role of Plant Defence Mechanisms

DOI: 10.1007/978-90-481-9489-6_9 In book: Arbuscular Mycorrhizas: Physiology and Function, pp.193-207

ABSTRACT

Arbuscular mycorrhizal associations imply a remarkable reprogramming­ of functions in both plant and fungal symbionts. The
consequent alterations on plant physiology have a clear impact on the plant response to biotic stresses. In this chapter we
discuss the effects of the mycorrhizal symbiosis on plant susceptibility/resistance to potential deleterious organisms, including
root and shoot pathogens, root parasitic plants and phytophagous insects, highlighting the mechanisms that may be operating
in each particular case. Special attention is given to the modulation of plant defence responses in mycorrhizal systems, as
it may affect all interactions. Finally we focus on the priming of jasmonate regulated plant defence mechanisms that seem
to mediate the induction of resistance by arbuscular mycorrhizas.

KeywordsBiotic stress-Bioprotection-Induced resistance-Priming-Plant defence-Biocontrol-Defence signalling-Jasmonates-Pathogens-Insects

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    • "Watson, 2004; Bi et al., 2007). More interestingly, AM symbiosis also enhances plant resistance against foliar pathogens such as fungal pathogens [e.g., Botrytis cinerea (Pozo et al., 2010; Fiorilli et al., 2011) and A. solani (Fritz et al., 2006)], bacteria [e.g., Xamantomonas campestris (Liu et al., 2007) and viruses (e.g., Tomato yellow leaf curl Sardinia virus (Maffei et al., 2014)]. Induction of pathogenesis-related (PR) proteins is believed an indicator of plant induced defense responses. "
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    ABSTRACT: Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.
    Full-text · Article · Oct 2015 · Frontiers in Plant Science
    • "Because of the lower sensitivity of fungal hyphae to metals compared with plant roots (Leyval & Joner 2001 ), a functional symbiosis with metaltolerant strains of AM fungi can provide plants with a survival strategy to cope with metal stress while still maintaining an adequate supply of nutrients such as P and N, through hyphal active absorption (Gaur & Adholeya 2004), thus contributing to the improvement of plant performance in metalcontaminated soils. INTERACTIONS BETWEEN ARBUSCULAR MYCORRHIZAL FUNGI AND PATHOGENIC FUNGI IN CAPSICUM ANNUUM L. Arbuscular mycorrhizal symbiosis imparts notable changes in host plant physiology, which have an impact on the plant response to biotic stresses (Pozo et al. 2010). In fact, some mechanisms may be involved in bio-protection by AM fungi against soil pathogens. "
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    ABSTRACT: The benefits of mycorrhizal inoculation on growth, yield and nutrition of plants are well documented. However, mycorrhiza use in pepper and sweet pepper crops ( Capsicum spp.) is still rarely exploited compared to other crops of economic importance. The current paper reviews the main aspects of the association between arbuscular mycorrhizal (AM) fungi and plants of pepper and sweet pepper. It includes topics about the effects of AM fungi on nutrition, growth and yield in Capsicum spp., paying particular attention to AM fungi–pathogen interactions, responses to some environmental stresses, as well as biochemical and physiological aspects of AM fungi–plant interaction in Capsicum annuum L.
    No preview · Article · Jul 2015 · The Journal of Agricultural Science
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    • "Endophytes also seem to affect the interaction between their hosts and other beneficial fungal microorganisms such as arbuscular mycorrhizal fungi (AMF) (Novas et al. 2005; Omacini et al. 2006). Benefits from the symbiosis with AMF, such as: improved soil structure , increased nutrient uptake and water usage efficiency , enhanced resistance to environmental stresses and protection against pathogens are well known (Borowicz 2001; Marulanda et al. 2003; Smith and Read 2008; Pozo et al. 2010). Mycorrhiza colonization is recognized to be significantly reduced by high phosphorus levels in soil (Nagy et al. 2009; Balzergue et al. 2011). "
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    ABSTRACT: Background and aims Plants often establish multiple simultaneous symbiotic associations with different microorganisms ; however, the way in which each sym-biont affects the other symbionts and the effects of these multiple interactions on plant performance are not well understood. The aim of this study was to evaluate how two different asexual Epichloë species modulate the establishment of arbuscular mycorrhizal fungi (AMF) in a wild forage grass under different soil fertilization levels. Methods We performed a completely randomized 12-month-long field experiment to evaluate the effect of two B. auleticus-endophyte ecotypes and two soil fertilization levels on the colonization of AMF, in seedlings and adult plants. Plant biomass and reproductive tillers production were also measured. Results The symbiosis, measured as the total extent of AM fungal colonization and frequency of arbuscules was significantly higher in Epichloë-infected plants and was not affected by fertilization either in seedlings or in adult plants. Plant biomass was increased by fertilization but no differences were observed due to the endophytic status. However, E+ plants produced more panicles than their E− counterparts. Conclusions Our findings strongly support the hypothesis of positive association between Epichloë endo-phytes and AMF in wild grasses, making this model important for agronomic improvement.
    Full-text · Article · May 2015 · Plant and Soil
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