Viral Disease in Plants

Viral disease in plants Introduction A virus is an organism that is very small and has nucleic acid, DNA or RNA molecules wrapped in a protective protein layer or capsid. This tissue is known to carry genetic information and carry out replication so that it will spread. The virus itself was first discovered by Adolf Mayer in 1887. At that time, Adolf Mayer saw yellow spot disease on tobacco leaves and it was contagious when applied to healthy plants.The history of the discovery of viruses began in 1883 by a German scientist named Adolf Meyer. Adolf researched tobacco plants. Adolf discovered tobacco with abnormal leaves. The leaves are yellowish in color and upon inspection there is liquid or mucus. The leaves suffer from mosaic disease. This disease causes stunted plants and mottled leaves. According to Adolf Meyer, tobacco mosaic disease can be transmitted. Adolf proved it by spraying extracts of tobacco leaves affected by normal plant mosaic disease. As a result, the previously normal leaves become yellowish green. Based on the results of his research, this disease is caused by very small microbes and for You have to see it using an electron microscope. Dimitri Ivanovsky conducted similar research. Dimitri managed to find a bacteria filter device. In his research, Ivanovsky applied filtered tobacco leaves affected by mosaic disease to normal plant leaves. As a result, the plant becomes infected. Dimitri concluded that the microbes that cause the disease are pathogenic and smaller in size than bacteria. Characteristics of Viruses Viruses are basically said to have characteristics like living creatures because they can reproduce themselves. However, viruses are also called non-living creatures because they do not have organelles like living cells. According to biologist from the United States, Neil A Campbell, the following are the characteristics of viruses: a. Can only live and reproduce within the living cells of otherorganisms. b. Requires nucleic acid to reproduce. c. Viruses are formed by a particle called a virion which contains only DNA or RNA. d. Viruses can be crystallized but the virus is still pathogenic if infected into a living organism. e. It has acellular nature or does not have cells, and does not have cell organelles. f. Meanwhile, according to Brum (1994) viruses have a very small size. In fact, it is smaller compared to bacteria. It is estimated that the size of the virus ranges from 20 nm-300 nm (1 nm = 1 x 10-9 m). Viruses cannot be seen with the naked eye or an ordinary microscope but must use a light or electron microscope. Plant viruses are organisms that are dependent, that is, they can only infect plants with the help of other factors, such as wounds or insect vectors. The number of viruses that have been found has reached thousands, of which 25 percent of the total number found are plant pathogens. Viruses can attack plants either individually or as complex viruses Viruses In plant cultivation, viruses are one of the causes of plant diseases which can cause significant losses both in terms of quality and quantity of production. Virus attacks on plants were actually known long before people knew about plant diseases caused by bacteria, but the cause was not yet clearly known.In 1882 and 1892, Meyer and Iwanoski reported that mosaic disease in tobacco was also caused by a virus that could be transmitted to healthy plants through juice from diseased plants. Furthermore, it is also known that these pathogens can also be transmitted by insects to healthy plants. Holmes was the first to report that tobacco plants (Nicotiana glutinosa) that were inoculated with the juice of the tobacco mosaic virus would cause local lesion symptoms. Meanwhile Stanley was the one who reported that the virus could be crystallized. In 1937, it was reported by Bawden and Pirie that virus particles consist of nucleic acid and protein. Generally, viruses that cause disease in plants differ from other pathogens in several ways. This is because viruses that cause plant diseases can only reproduce in their host cells. Besides that, these viruses can be crystallized for quite a long time without losing their infectivity. The special characteristics of viruses that are not shared by all other causes of disease apart from the two above are: 1). Only has one type of nucleic acid, namely deoxyribunucleic acid (DNA) or ribonucleic acid (RNA), 2). Reproduce only from nucleic acids, 3) cannot grow or divide, 4) do not have genetic information for the synthesis of the Lipman system, namely a system that uses enzymes to produce high potential energy and 5) viruses are parasitic, namely using host cell ribosomes. , where such things are not found in other disease causes such as fungi, bacteria and others. Plant viruses are actually simple macro molecules (size between 20-1000 nm), which are passive when they enter the host plant cells they infect. Viruses consist of ribonucleic acid (Ribo nucleic acid=RNA) or dioxyribonucleic acid (dioxy ribo nucleic acid=DNA), covered by a protein or lipoprotein coat.The definition of the virus itself is undergoing very rapid changes in line with changes in biomolecular, chemical and physical virus detection and identification technology. The general definition of a virus is a parasite that can be transmitted, whose nucleic acid genome weighs less than 3 x 108 daltons and requires ribosomes and other components of host cells to reproduce. Viruses are obligate parasites so they can only live and develop in living cells. The shapes of plant virus particles vary, including balls (isometric), rods, flexible rods, threads, bullet-like and twin shapes (Gemini). Plant viruses do not contain enzymes, toxins or other substances like other pathogens that are involved in pathogenicity and cause various symptoms in the host plant. Infection occurs when viral synthesis is complete. Symptoms of peanut plants infected with viruses generally include stripes, faint stripes, crackling, curling, yellowing, necrosis, shoot death and others. Viral infections are systemic so that the virus spreads to all parts of the plant. The nomenclature for viruses is still evolving. Plant disease researchers name viruses based on the name of the host plant where the virus is found and the symptoms that are clearly visible, for example peanut mottle virus (PMoV). Initially viruses were thought to be a stable form and each disease was thought to be caused by a different virus. However, further research revealed that: (1) The virus can consist of various strains that can cause very different symptoms on the same host plant; (2) different viruses (their collective species) can cause the same symptoms on the same host plant, and (3) some diseases can be caused by mixtures of viruses that are unrelated to each other. The final nomenclature proposed is a cryptogram model which consists of four pairs of symbols and contains two systems including the usual name and containing information about the nature of the virus. The first pair is the type of nucleic acid/chain (strandedness), R=ribonucleic acid (RNA), D=deoxy ribonucleic acid (DNA). Strand type symbols 1=single strand, 2=double strand