Its Dmitri Ivanowsky ....who discovered virus while studying tobacco mosaic disease...he called it as infectious agent...Beijernick...called it as Contagium Vivum Fluidum i.e. contagious living fluid....W.M stanley-> said that virus i.e. TMV can be crystallised...Fraenkel Conrat..->confirmed that the genetic material of TMV is RNA...

Scientists who discovered virus
The discovery of viruses is credited to two different scientists in the old and new NCERT textbooks.

Old NCERT:
- In the old NCERT textbooks, the discovery of viruses is attributed to a Dutch microbiologist named Martinus Beijerinck.
- Beijerinck is known for his work on tobacco mosaic disease, where he coined the term "virus" to describe the infectious agent responsible for the disease.
- He is considered one of the founding fathers of virology for his pioneering research in this field.

New NCERT:
- In the new NCERT textbooks, the discovery of viruses is attributed to a Russian scientist named Dmitri Ivanovsky.
- Ivanovsky is known for his work on the tobacco mosaic disease as well, where he first observed that the infectious agent could pass through a filter that blocked bacteria.
- This experiment led him to conclude that there must be a smaller, filterable agent causing the disease, which he called a "virus."

Explanation:
- Both Beijerinck and Ivanovsky made significant contributions to the field of virology by independently discovering and studying viruses.
- While Beijerinck is more commonly credited with the discovery in older textbooks, Ivanovsky's work is also recognized in newer sources for his groundbreaking experiments that laid the foundation for our understanding of viruses.