History of Plant Virology
1. Virus disease of plants was known long before the discovery of bacteria.
i) Breaking of flower colour of tulips (as early as 1576).
ii) Transmission of leaf variegations from the scion to the stock of woody plants ( as early as 1700).
2. Tobacco mosaic was identified by Swietch in Holland in 1857.
3. Adolph Mayer (1886) was the first to point out that tobacco mosaic is readily transmissible and infectious. Believed that bacteria are the cause of the disease.
4. Iwanowski (1892) confirmed some of the results Mayer. He demonstrated that the power to infect was lost if the sap was previously heated. He reported that infectiousness was retained even when sap was passed through bacteria proof filters.
5. Bejierink (1896) demonstrated that tobacco mosaic infectious agent could diffuse through an anger membrane and concluded that tobacco mosaic was caused by a non-corpuscular ‘ Contagium vivum fluidum’ which he called as Virus.
6. Hashimoto (1894) showed transmissible lity of rice dwarf disease by leaf hopper ( Nephotettix apicalis var. cincticeps).
7. Stanley (1935) crystallized tobacco mosaic virus with ammonium sulphate and concluded that the virus was an autocatalytic protein that could multiply within the living cells. He considered that virus was a globulin containing no Phosphorus. For his discovery he was awarded a Nobel Prize.
8. Bawden and Pirrie (1936) described the isolation from TMV infected plants of a liquid crystalline nucleoprotein containing nucleic acid of the pentose type. They showed that the particles were rod shaped.
9. Kausche, Pfankuch and Ruska (1939) saw virus particles for the first time with the electron microscope. They confirmed that TMV was rod shaped.
10. Muller (1942): Williams and Wycoff (1944) developed shadow casting technique with heavy metals which was useful for determining the overall size and shape of the virus particles.
11. Markham and Smith (1949) isolated TYMV and showed that it contained (1) An infectious nucleoprotein (about 25% ) and (2) non inferious protein.
12. Morel and Martin (1952) showed that virus free plants could be obtained from totally infected parents using meristem tip culture.
13. Kassanis (1954) showed that virus could be eradicated from infected plants by high temperature treatment.
14. Gierer and Schramm ( 1956) showed that the protein could be removed the virus and that the nucleic acid carried the genetic information so that inoculating with the nucleic acid alone cause infection and could reproduce the complete virus.
15. Kassais (1962) was the first to describe the satellite virus ( Sv) which has been found only in association with tobacco necrosis virus.
16. Doi et.al. (1967) recognised MLO disease (Yellow witches broom).
17. Ishiie et.al. (1967) showed that the MLO bodies and the symptoms disappeared temporarily when the plants were treated with tetracycline antibodies.
18. Black and Markhan (1963); Miura et.al. (1966) showed that wound tamout and rice dwarf viruses contain double started RNA.
19. Shephard et.al. (1968) showed that cauliflower mosaic virus contains double stranded DNA.
20. In 1971, Diener determined that the potato spindle tuber disease was caused by a small (250- 400 bases long), single stranded circular molecule of infectious RNA which he called a viriod.
21. Windsor and Black (1972) observed RLO in the phloems of clover plants infected with clu leaf disease.
22. Davis and Worley (1973) observed motile; helicle microorganism associated with corn stunt disease and named it spiroplasma.