Molecular recognition of fungal pathogens and activation of plant immune response

Abstract

Specific recognition mechanism in host-parasite interaction for successful establishment of pathogen for disease development or rejecting the entry of the pathogen by the host have been discussed. During incompatible and compatible interactions a large number of signals are exchanged between the host and the pathogen. During early infection stages in the plants, numerous signals are produced that lead to development of hypersensitive reaction which is intimately linked with the expression of molecular and chemical markers such as salicylic acid and pathogenesis related proteins and finally phytoalexin synthesis for activation of plant defences. On the other hand, pathogens may also generate toxic metabolites which can suppress defences in plants and develop disease symptoms. Recognition of pathogen associated molecular patterns (PAMP) that bind to plant receptors activate induced resistance. In non-host plants, a multitude of PAMPs are known to activate receptor-mediated defence response and recognition of these signals probably triggers defence responses in natural plant–pathogen interactions. Virulent pathogens exert selective pressure on host plants which has led to the evolution of resistance R genes. The R-genes can specifically recognize different strains of pathogens as well as race specific factors paving the way for disease resistance specific to pathogen races or plant cultivars. The potential use of acquired and induced immunity has been explored in strengthening strategies for crop disease management. Agriculturally important microorganisms have been shown to induce resistance in crops. This may lead towards efficient bioinoculant formulation and delivery system which could become important inputs leading to a resilient agriculture.