Cocoa Swollen Shoot Virus Transmitted Mainly Insect Vectors Biology Essay
Cocoa Swollen Shoot Virus ( besides known as CSSV, Cacao Swollen Shoot Virus, Theobroma virus 1, or chocolate tree mottled leaf virus ( Brunt et al, 1996 ) ) is a Baltimore Class VII virus of the genus Badnavirus, and is transmitted chiefly via insect vectors. It has great fiscal branchings, as one of its hosts is Theobroma chocolate tree, besides known as the Cocoa tree, which produces chocolate beans, vital for the production of cocoa worldwide. Research into CSSV seems to be comparatively seldom published, with roars in research being noted in the 1930s to the 1970s, but so a important oversight in research ( that will be addressed subsequently ) before the mid 2000s, when engineering increased to the point that the genome of the virus itself could be read. Most of the research is performed in CSSV ‘s native state of Ghana, West Africa. It was foremost officially described by Posnette ( 1940 ) and subsequently classified by Brunt and Kenten ( 1960 ) .Brunt and Kenten ( 1963 ) besides went on to plan the footing of the presently accepted manner of purification of CSSV. This included macerating infected chocolate leaves in a proteinaceous fluid that extracted the virus, which could so be separated from the remainder of the fluid by centrifugation.
In the same experiment, they besides discovered that egg albumen, blood albumen, casein and conceal powder were all effectual at maintaining the virus alive and morbific so that it could be studied. This method went on to be used and altered somewhat by Adomako et Al ( 1983 ) who simplified the procedure by making an antiserum to the virus that was useable in an ELISA check, insulating CSSV atoms utilizing multiple washes. Lot et Al ( 1993 ) used a different method affecting “ a combination of celite filtration, polythene ethanediol concentration, and sucrose denseness gradient centrifugation ” , utilizing the isolates to analyze the CSSV genome, placing it as a two-base hit stranded DNA virus.Figure 1 – An icosohedral virion mirid bug. One such as this is the mirid bug that CSSV uses, giving it a bacillar visual aspect under an negatron microscope.
Isolates of CSSV have been examined under negatron microscopes and described as non-enveloped bacilliform viruses ( Figure 2 ) . This is unusual, as most icosohedral viruses have a approximately spherical form, while CSSV is more rod-like, connoting that it may be an enveloped coiling virus. However it was discovered that it could n’t be a coiling virus as it has a round two-base hit stranded DNA genome, as opposed to the RNA genome that coiling viruses contain.
It has besides been demonstrated that all Badnaviruses have a similar extended icosohedral rod-like construction, and all are works viruses.The two-base hit stranded nature of CSSV was discovered by Lot et Al ( 1991 ) utilizing nuclease sensitiveness trials. They besides discovered the fact that there are 2 parts in the 7.4 kbp length of its genome that are made up of individual stranded Deoxyribonucleic acid. This survey besides determined that CSSV belongs to a peculiar type of works virus identified by Lockhart ( 1990 ) that contain round two-base hit stranded DNA.HistoryCSSV has been found to impact chocolate trees in Western Africa ( Figure 3 ) though it has been reported in other countries, such as Trinidad, in Northern South America and Sri Lanka. In Trinidad, nevertheless, there are merely 2 presently identified strains, known as A and B ( Baker and Dale, 1947 ) .
In Ghana peculiarly CSSV has been a major job for chocolate husbandmans since the 1936, when the foremost reported instance was discovered by W.F. Steven ( F.K Danquah, 2003 ) . In those times the lone manner to command a works virus was to destruct the affected workss.
Unfortunately for the chocolate husbandmans in Ghana, approximately 50 % of their trees were destroyed in the involvements of commanding the virus.By 1938 the first lab was set up to analyze CSSV in Ghana, though the Second World War badly limited its research. In 1944 it was transformed into the West African Cocoa Research Institute ( WACRI ) , which showed that the distribution of CSSV was larger than antecedently thought, and was endangering environing states every bit good. By 1947, it had spread to the environing states of Le Cote D’Ivore ( known in English as the Ivory Coast ) , Sierra Leone, Nigeria and Togo and reduced Ghana ‘s end product of chocolate by about 50 % , decimating their harvests.Figure 2 – Scientists with the CSSVDC analyzing samples of CSSV infected plantsIn the early 1950s, a UN deputation decided that the best response to the job of CSSV was to bring forth and works CSSV immune intercrossed trees, though it was n’t until 1962-3 that this program really began to do advancement. The duty for the spread of the virus was removed from the authorities, who had been firing the trees until this clip, and passed to the husbandmans themselves. The husbandmans were supplied with CSSV immune workss produced by scientists who bred chocolate workss with a works resistant to many diseases known as Amazonia, or F-2, to bring forth CSSV immune chocolate workss.
These workss were distributed to the chocolate husbandmans under the label of Tafo Hybrid.Farmers implemented the UN ‘s program by cutting down their ain chocolate trees and firing them themselves, replacing them with the new Tafo Hybrid trees. An added advantage was that these new trees had a higher output, and a faster growing clip. Since so, husbandmans have been firing off their septic trees, killing the virus, and replacing them with the new immune trees.Because of these steps that have been put in topographic point to command the spread of CSSV, it is mostly no longer a job for chocolate husbandmans, and could assist to explicate why there was small research being done into it from the 1970s to the mid-2000s. That is n’t to state that it has been wholly eradicated ; CSSV is still around in Ghana, though the sum of trees that are infected has been greatly reduced from the 1930s to 1960s, when at times up to 70 % of the harvests may hold been infected at any given clip. The go oning being of CSSV is being combated by assorted boards and commissions, most notably the Cocoa Swollen Shoot Virus Disease Control Unit ( CSSVDC ) that was set up in 1994 by the Ghana Cocoa Board to halt further spread of the virus.
Their web site, which gives a little sum of history on the creative activity of the unit, can be found at hypertext transfer protocol: //www.cocobod.gh/control_history.php.EpidemiologyFigure 4 – Several trees that are vulnerable to CSSV infection. From left to compensate, they are: Adasonia digitata, Bombax brevicuspe, Ceiba chlamydantha, Cola gigantea and Theobroma chocolate tree, the tree that produces chocolate beans used in doing chocolate.
CSSV has been reported in several different species of chocolate trees ( Brunt et al, 1996 ) , including Adansonia digitata, Bombax brevicuspe, Ceiba chlamydantha, C. Pentandra, Cola chlamydantha, C. gigantea, the Corchorus household, Sterculia tragacantha and most significantly Theobroma chocolate tree, the tree from which chocolate is farmed ( Figure 3 ) .T.
chocolate tree is the works from which chocolate is farmed. The fiscal reverberations of the infection of this tree being why it is the most normally studied works when research is being conducted into CSSV. Cocoa is one of Ghana ‘s chief exports, and an of import portion of their economic system. Almost all of the instances have been reported in West Africa, arising in Ghana, and being found in Le Cote D’Ivore ( The Ivory Coast ) , Sierra Leone, and Togo, all environing Ghana. There are no reported instances in the other states environing Ghana.
That is n’t to state that the virus does n’t be at that place ( though it is theoretically possible that is the instance ) , merely that no trees have been symptomatically affected. The distribution of the virus seems to bespeak that it is affected by the temperature, as all of the reported instances were found around the equator. There have besides been trees found to be immune to the virus, including those of the households Amarantheceae, Chenopodiaceae, Cucurbitaceae ( that is made up of modern Citrullus vulgariss, squashes, Cucumis sativuss and other such melons, calabashs or curcurbits ) , Euphorbiaceae, Malvaceae ( the household that the susceptible Theobroma chocolate tree belongs to ) and Solanaceae.