Figure 1.

Endophytic biocontrol mode of defense mechanisms against pathogens. Stage 1: Bacteria and fungi invade the plant through a wound or stomatal opening. Stage 2: Both bacteria and fungi degrade the plant cell wall with the aid of enzymes, secondary metabolites, or virulent factors. Bacteria proliferate through the intercellular space, whereas fungi invade the plant by a biotrophic or necrotrophic mechanism using appressorium (A), germ tube (G.T.), and spore and proliferate in the cells of the plant. Endophytes provide defense against pathogens through various modes of action, such as (a) hydrolytic enzyme; (b) mycoparasitism; (c) siderophore; and (d) SAR and ISR modes of action. Note: ISR, induced systemic resistance; JA, jasmonic acid; MAMPs, microbe-associated molecular patterns; NPR1, non-expressor of pathogenesis-related genes 1; PAMPs, pathogen-associated molecular patterns; PRRs, pattern recognition receptors; PTI, pathogen-triggered immunity; SA, salicylic acid; SAR, systemic acquired resistance.