Induced systemic resistance in rice

Abstract

Plants possess a plethora of defense mechanisms that respond to both biotic and abiotic stresses. The response of a plant to various pathogens and pests can vary dependent on factors such as host variety, strain, as well as environmental factors. How quickly a plant responds to these stresses will determine the level of resistance of a plant species. The SAR and ISR mechanisms in plants work together to provide the host with protection against pathogen and pest attacks. Unlike SAR, ISR is induced by nonpathogenic allies from belowground in the form of plant growth promoting bacteria. ISR is induced in the root and in foliar tissue and is able to provide the host plant with systemically induced resistance against a broad spectrum of microorganisms. Selected strains of plant growth promoting rhizobacteria suppress diseases and pest infestation by inhibition of pathogens/pests as well as resulting in the induction of systemic resistance in planta. In rice these organisms have been known to activate the JA/ETH and auxin pathways. Due to the higher levels of endogenous SA in rice, the SA independent pathways are a preferred way of inducing resistance within the rice host. There are various types of determinants that have been implicated to play a role in ISR. These determinants can either work individually or in combination to induce ISR in plants. From in vitro, greenhouse and field studies on rice, several strains of bacteria such as Pseudomonas spp., Bacillus spp., Serratia spp., and Azospirillum spp. have been listed as organisms with potential to function as biofertilizers and biopesticides in rice.