The first arena of combat between plants and pathogens is the extracellular space between the cell wall and plasma membrane. In the initial stage of infection, bacteria, fungus, and oomycetes that colonise the living plant tissues are contained in this small area. Studies focusing on the in-planta interaction between the host and the pathogen were conducted using techniques for the isolation and normalisation of apoplastic proteins as well as the level of secretome research at the time. The complex process of plant-pathogen interaction is mediated by molecules derived from both the pathogen and the plant, namely proteins, carbohydrates, and lipopolysaccharides. The viruses' secreted chemicals play a crucial role in determining their pathogenicity and enabling effective colonisation within the host. Conversely, chemicals from plants are involved in the identification of these pathogens in order to trigger the defence response. The detection of microbial elicitors by plant receptor proteins mediates the first interaction between the plants and bacteria, which occurs in the apoplast. Plant immunity relies on cell-autonomous processes that are comparable to animal innate immunity, but to make up for the absence of an adaptive immune system, plants have a vastly larger recognition repertoire. Current studies on pathogen biology are beginning to explain how these organisms exploit host immunity to produce disease, and ongoing research is exposing the ability of the plant immune system to recognise foreign substances.  With increased salicylic acid-induced resistance in numerous viral pathogens and absolute resistance to P. syringae pv. tabaci, the bO gene was expressed in tobacco. Tobacco plants were rendered insensitive to phaseolotoxin thanks to the argK gene expressing ornithine transcarbamylase, and transgenic beans were entirely immune to P. syringae pv. Phaseolicola. Host plants frequently exhibit polymorphism resistance to various pathogen strains or races, which is regulated by a single gene, in plant-pathogen interactions. Disease resistance governed by recessive genes frequently takes the form of passive resistance, in which the pathogen is prevented from using the machinery of the host cell. When a parasite species can only infest a single plant species, it reaches the first level of specificity. It explains why a plant that is sensitive to a certain parasite is also resistant to most others and it permits the following categories to be defined: I races, biotypes, pathotypes, or strains of nematodes; ii) pathovars (pv.) or varieties (var.) of bacteria; iii) pathotypes or strains of viruses; and iv) forma specialis (f.sp.) or variants (var.) of fungi, bacteria, and viruses.

Regards

Managing Editor

Larry Taylor

Agricultural and Biological Research