Resistance and defence
In the process of Induced resistance and defence activation, chemical compounds produced by soil organisms trigger the plant to enhance its state of resistance and defence leading to the protection of non-exposed plant parts against future attack by pathogenic microbes and herbivorous insects. Two different sets of actors can be involved in this process. First, the plant pathogens and pests themselves can trigger the induced resistance and defence response in plants. In this case, the process carries the more specific name of ‘systemic acquired resistance (SAR)’ and is associated with the accumulation of salicylic acid and the induction of pathogenesis-related proteins. Second, plant growth-promoting non-pathogenic soil organisms can also activate plant resistance and defence. In this second case the more specific name for the process is ‘induced systemic resistance (SIR)’, which involves the jasmonic acid and ethylene pathways.
Induced resistance and defence activation is considered under the Disease and Pest Management function only. Through the activation of induced resistance and defence mechanisms, soil organisms are ultimately able to increase plant response to pathogens and pests, limiting their damages and controlling the damages they might cause to plants.
Induced resistance and defence activation can be estimated by measuring the inducement of plant resistance and defence mechanisms activity with bioassays carried out on plants[1],[2]. Other methods rely on molecular quantification of functional genes and transcripts involved in activation of induced resistance and defence with qPCR and RT-PCR, respectively[3],[4].
[1] Liu L et al. 1995. Induction of systemic resistance in cucumber against Fusarium wilt by plant growth-promoting rhizobacteria. Phytopathology 85:695-698.
[2] Abbasi S et al. 2019. Streptomyces Strains Induce Resistance to Fusarium oxysporum f. Sp. Lycopersici Race 3 in Tomato through Different Molecular Mechanisms. Frontiers in Microbiology 10.
[3] Imperiali N et al. 2019. Relationships between Root Pathogen Resistance, Abundance and Expression of Pseudomonas Antimicrobial Genes, and Soil Properties in Representative Swiss Agricultural Soils. Frontiers Plant Science 29.
[4] De Coste NJ et al. 2010. Verticillium dahliae alters Pseudomonas spp. populations and HCN gene expression in the rhizosphere of strawberry. Canadian Journal of Microbiology 56: 906-915.