Host Versus Nonhost Resistance: Distinct Wars with Similar Arsenals

Abstract

Plants face several challenges by bacterial, fungal, oomycete, and viral pathogens during their life cycle. In order to defend against these biotic stresses, plants possess a dynamic, innate, natural immune system that efficiently detects potential pathogens and initiates a resistance response in the form of basal resistance and/or resistance (R)-gene-mediated defense, which is often associated with a hypersensitive response. Depending upon the nature of plant-pathogen interactions, plants generally have two main defense mechanisms, host resistance and nonhost resistance. Host resistance is generally controlled by single R genes and less durable compared with nonhost resistance. In contrast, nonhost resistance is believed to be a multi-gene trait and more durable. In this review, we describe the mechanisms of host and nonhost resistance against fungal and bacterial plant pathogens. In addition, we also attempt to compare host and nonhost resistance responses to identify similarities and differences, and their practical applications in crop improvement.

Cytological aspects of incompatible and compatible interactions between rice, wheat and the blast pathogen Pyricularia oryzae

“…The rice-and wheat-P. oryzae interactions follow the gene-for-gene interaction proposed by Flor (1971), in which a specific race of P. oryzae carrying an avirulence gene is incompatible with a certain cultivar that contains the respective resistance gene (host resistance) (Liu et al, 2007;Zhan et al, 2008). Non-host resistance is usually more complex than host resistance, due to the involvement of multiple pathways (Gill et al, 2015). According to McDonald and Linde (2002), agroecosystems that are based on the widespread deployment of single, major resistance genes place strong directional selection on the pathogen population, which consequently enhances the risk that plants will lose their resistance to diseases.…”

“…This coevolution, which largely determines the host-pathogen interactions, co-speciation, host-shift speciation and host jump, plays a key role in the adaptation of pathogens to new plant species (Gill et al, 2015). The rice-and wheat-P. oryzae interactions follow the gene-for-gene interaction proposed by Flor (1971), in which a specific race of P. oryzae carrying an avirulence gene is incompatible with a certain cultivar that contains the respective resistance gene (host resistance) (Liu et al, 2007;Zhan et al, 2008).…”

“…According to McDonald and Linde (2002), agroecosystems that are based on the widespread deployment of single, major resistance genes place strong directional selection on the pathogen population, which consequently enhances the risk that plants will lose their resistance to diseases. In contrast, non-host resistance is not pathogen-race-specific and, therefore, decreases the risk of resistance suppression by the pathogens (Gill et al, 2015).…”

Asian Soybean Rust Resistance: An Overview

“…Race-specific resistance is controlled by single R genes and generally less durable. In contrast, race-nonspecific resistance is a polygenic trait and more durable [44].…”

“…However, some pathogens can secrete effectors to evade recognition by plant PRRs and to promote pathogen growth and virulence, called effectortriggered susceptibility (ETS). In response to ETS, host plants trigger R proteins to interact directly or indirectly with pathogen effectors or avirulence (Avr) proteins, and induce a stronger defense response, referred to as effector-triggered immunity (ETI) [44]. ETI triggers salicylic acid (SA) biosynthesis and signaling, leading to local and systemic acquired resistance (SAR) against biotrophic pathogens.…”