Phytoplasma

Phytoplasma

Biology

Phytoplasma belongs wall-less bacterial group (Class Mollicutes). Previously know as mycoplasma like organisms (MLOs), phytoplasma are obligate, phloem-residing plant pathogens. Phytoplasmas were discovered by electron microscopy of ultra thin sections of infected plants by Japanese scientists Doi et al. (1967). These are ranging between 0.2 to 0.8 ┬Ám and are too small to be resolved by light microscope. Phytoplasmas are surrounded by tipple-layered plasma membrane and hence have a fluid shape, i.e., they are pleomorphic in nature and changes their shape. The membrane of phytoplasma consists of lipoprotein. Phytoplasmas are although wall-less, they closely related to the Gram-positive bacteria at the genetic level. Because of the lack of cell wall, they are resistant to the peptidoglycan-targeting antibiotics like, penicillin. Phytoplasmas are among smallest know cells and smallest genome of about 680-1600 kb. Their genome consists of both DNA as well as RNA. Little leaf, phyllody, witches' broom, big bud and flower virescence are symptoms of the diseases caused by phytoplasmas. Phytoplasmas parasitize following plants:
Sr.PlantFamily Disease
1.BrinjalSolanaceaeLittle leaf of brinjal
2.SesamumPedaliaceae Phyllody
3. Sugarcane  PoaceaeGrassy shoot
4. PeachRosaceae Rosette 
5. Potato Solanaceae Stolbur of potato 
6. Tomato Solanaceae Big bud of tomato 

Phytoplasmas are transmitted plant to plants through the insects (leaf hoppers), by seeds and other plant propagating materials and through the dodder.

References

  • Doi, Y., Teranaka, M., Yora, K., and Asuyama, H. (1967). Mycoplasma or PLT grouplike microrganisms found in the phloem elements of plants infected with mulberry dwarf, potato witches’ broom, aster yellows or pawlownia witches’ broom. Ann. Phytopath. Soc. Japan. 33, 259–266. doi:10.3186/jjphytopath.33.259