Pathogen

Pathogen:- A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes.

Major Types of Plant Pathogens:- The breath of diversity among plant pathogens is truly marvellous. You can largely group them into four main categories:

i. Bacteria:- Gram-positive and gram-negative bacteria like _Pseudomonas_, _Xanthomonas_ are prime examples.

ii. Fungi:- They are maybe the most common plant pathogens. _Fusarium_, _Verticillium_, and _Rusts_ fall under this category.

iii. Viruses:- These tiny pathogens cause significant damages like Tobacco Mosaic Virus.

Parasitic Plants: Some plants tend to be parasitic, for example, _Dodder_. 

iv. Nematodes:- Nematodes are thread-like roundworms that live in a wide range of environments including soil and fresh and salt water. There are species of nematodes that feed on fungi, bacteria, protozoans, other nematodes, and plants. They can also parasitize insects, humans, and animals.