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

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

0 Bookmarks
 · 
413 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The worldwide important crop tomato is attacked by various pathogens, for which management is still primarily reliant on fungicides despite increasing concerns and constraints on their use. Other approaches are investigated, including the use of biocontrol organisms to manage tomato diseases. In this review we discuss and compare the interaction of major biocontrol fungi (BCF) with tomato, including the endophytic arbuscular mycorrhizal fungi and Piriformospora indica, the free-living opportunistic symbionts Trichoderma spp. and non-pathogenic Fusarium oxysporum, as well as the oomycete Pythium oligandrum. We cover recent advances that have been made in unraveling biocontrol modes of action against the most important tomato pathogens, encompassing direct effects of the BCF on pathogens and their indirect effects through the plant, with a main focus on induced systemic resistance. It is an exciting era for the study of biocontrol tripartite interactions, with the emergence of next-generation sequencing tools and the higher pace at which new genomes are being sequenced nowadays, as was recently also achieved for tomato. In addition, plant pathology and biocontrol research domains are increasingly reaching out to each other, because of the parallels that we are only beginning to discover between the interactions of beneficial and detrimental micro-organisms with a plant. Considering the enormous technological possibilities at hand today, this seems a timely opportunity to review the most recent advances in this field and to anticipate to what is ahead of us, discussing breakthroughs expected in our understanding of biocontrol interactions and remaining hurdles on the way to reach them.
    Biological Control 07/2014; 74. DOI:10.1016/j.biocontrol.2014.04.004 · 1.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Legumes develop different mutually beneficial symbioses with soil microbes, such as arbuscular mycorrhizal (AM) fungi, nodule bacteria and plant growth promoting bacteria. Symbioses supply the plants with nutrients (predominantly with nitrogen and phosphorus), protect them from pathogens and abiotic stresses and improve soil microbial biodiversity and fertility. The synergistic activity of beneficial soil microbes (BSM) on the plants has great importance for the use of multi-component symbiotic systems in low-input sustainable environmentally-friendly agrotechnologies. However, the complex nature of the AM symbiosis when in a multi-component symbiosis (plant-fungus-bacteria) creates complications for the fungus to produce AM fungal propagules and poses questions (a) about the effectiveness of the fungus per se in interactions with the plants, without associates, and (b) about the necessity of using sterile/axenic conditions for the production of the AM fungi based inoculants because of any mixing and competition by microbes from the inoculants with the local soil microbial consortia. The legume genes controlling interactions with BSM (including genes responsible for effectiveness of such interactions) should be considered as a united genetic system. The plant genome is more stable than that of microbes and therefore crop plants should select beneficial microbes and control the effectiveness of the whole plant-microbe system in the field for the benefit of the crop and therefore of human beings. There is clearly a need to breed legume crops with improved performance under sustainable conditions involving interactions with BSM and optimising the use of agrochemicals.
    Symbiosis 12/2013; 58(1-3). DOI:10.1007/s13199-013-0226-2 · 0.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ectomycorrhizal fungus Amanita vaginata can control damping off (Rhizoctonia solani) and promote growth of Pinus tabulaeformis seedlings. The aim of this study was to investigate whether reactive oxygen species and antioxidative enzymes play a role in preventing damping off in ectomycorrhizal roots. Two months after P. tabulaeformis roots were inoculated with A. vaginata, the roots were inoculated with R. solani. During the early stages (2–96 h) of R. solani infection, the quantity and localisation of hydrogen peroxide and the activities of superoxide dismutase and catalase were evaluated. A burst of hydrogen peroxide occurred in ectomycorrhizal roots and in non-ectomycorrhizal roots when attacked by R. solani. In ectomycorrhizal roots, hydrogen peroxide production peaked 12 h after R. solani inoculation, which coincided with an increase in the activity of superoxide dismutase and catalase, whereas in non-ectomycorrhizal roots, hydrogen peroxide production peaked 24 h after R. solani inoculation and did not coincide with changes in superoxide dismutase or catalase activity. The imbalanced activities of superoxide dismutase and catalase might cause excessive accumulation of hydrogen peroxide and consequent damage to cell walls. Electron microscopy revealed that there was a positive correlation between hydrogen peroxide levels and the number of amyloplasts, with seedlings inoculated with A. vaginata and/or R. solani showing higher levels. These results indicated that A. vaginata inoculation enhanced damping off resistance and stimulated seedling growth, which may be due to the activation of a burst of hydrogen peroxide and its scavenging enzymes and the production of biochemical substances such as amyloplasts.
    European Journal of Plant Pathology 10/2012; 134(2). DOI:10.1007/s10658-012-9996-2 · 1.71 Impact Factor

Full-text

Download
263 Downloads
Available from
Jun 3, 2014