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Tomato Yellow Leaf Curl Virus Tylcv Infection Biology Essay

Tomato, Solanum lycopersicum belongs to the household Solanaceae and genus Solanum, which has served the human being with many nutrient workss. Almost 96 genra and 2800 species of Solanaceae have been reported within the subfamilies Solanoideae, Cestroideae and Solanineae ( Nee et al. , 1991 ) . In the past the tomato was named as Lycopersicon esculentum while tree tomato was termed as Cyphomandra betacea but now it is being replaced by the name S.betaceum. Some Solanums in South America like cocona, pepino and Solanum quitoense are besides of importance ( Heiser et al. , 1999 ) . Harmonizing to FAO statistics, tomato ( Solanum Lycopersicon ) has been cultivated over an country of 520 1000s hectares with an mean production of 7420 1000 matric dozenss ( FAO, 2002 ) . This world-wide distribution of tomato reflects its importance and insistence. Tomato harvest is perennial in nature and is being grown in moderate climatic parts as an one-year. China is on the top place with an mean production of 38 million tones, followed by US ( 25 million dozenss ) and so Turkey, India and itlay ( FAOSTAT, 2008 ) . Suitable dirt for tomato cultivation is deep loamy and good drained with a PH of 6.2-6.8, but it can even turn in different types of dirts. Due to warm season harvest, tomatoes do non digest the iciness or hoar.

Though tomato is native to South America, it was introduced in Europe by early adventurers and was known as Apple of Love in France and Itlay. Thomas Jefferson, a former US President used to raise this harvest for his invitees during 1781. On the other manus tomatoes were non grown in US until 1835 because it was thought to be toxicant at that clip. Tomato is really healthful due to its alimentary values. One medium size tomato provides with 57 % of vitamin C, 25 % of vitamin A and 8 % of Fe though it has merely 35 Calories. Besides this it has besides been used in salads, pickles, juices, and bakeshop and so on. New cultivars appear in market each twelvemonth spread outing and bettering disease opposition.

Tomato is the most popular in today ‘s place garden but it is ever non popular. This delightful harvest is being faced by many menaces in the signifier of plagues, bacterial and viral diseases. There are certain geminiviruses impacting the tomato harvests. One of the of import virus impacting the tomato production is Tomato Yellow Leaf Curl Virus ( TYLCV ) was described in early 1960ss. TYCLV can infect 15 species in five different households.

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In 1959, in Israel, the husbandmans were convinced by Government to replace the Marmande assortment of tomato with money Maker for the intent of export. After transfering of this assortment in the field, bulk of the harvest was affected by an unknown disease. Symptoms showed stunting, stiff shoots, smaller and deshaped foliages. Curling down of the foliages and upward curling of foliage borders was besides observed. Young workss infected with this virus seldom produce any fruit ( Cohen and Nitzany, 1960 ) . Later on studies were done and it was confirmed that this disease was transmitted by whitefly with the controlled transmittal experiments in the research lab. It was besides observed that Marmande tomato was every bit susceptible as Money Maker to this disease which was found to be viral in nature ( Cohen and Nitzany, 1960 ) .This virus was named as Tomato Yellow Leaf Curl Virus ( TYLCV ) by Professor I. Harpaz of the Hebrew University ( Cohen and Nitzany, 1964 ) . Similar disease symptoms were besides observed in Jordan vale tomatoes every bit early as 1929 ( Avidov, 1944 ) . The onslaught or eruption of this disease was ever accompanied by a big population of whiteflies ( Cohen and Berlinger, 1986 ) . This virus was isolated in 1988 ( Czosnek et al. , 1988 ) while the geminate form of the viral mirid bug was foremost observed in 1980 ( Russo et al. , 1980 ) . It took another three old ages to do the reproduction and to concatenation this virus ( Navot et al. , 1991 ) .

Bing old universe virus and its limited geographical distribution, it was non considered so of import at that clip until its eruptions of B biotype of vector Bemisia tabaci in 1980 particularly in European and Mediterranean parts ( Czosnek et al. , 1990 ) and besides damaging in Middle East ( Cohen and Harpaz, 1964 ; Cohen and Nitzany, 1966 ) . Subsequently on this virus established its place destructing all the harvest of tomato during early 1970ss ( Abak et al. , 1991 ; Mazyad et al. , 1979 ) . This virus has been reported throughout the universe in Israel, Itlay, Egypt ( Gallitelli et al. , 1991 ; Credi et al. , 1989 ) , in Asia including Taiwan, Thailand ( Green et al. , 1987 ; Thanapas et al. , 1983 ) and African states like, both eastern and western Africa including Nigeria, Mali and Senegal ( Defrand et al. , 1985 ) , and Central America and Caribbean including Dominican Republic ( Nakhla et al. , 1994 ; Wernecke et al. , 1995 ) have been reported of this virus. This virus contains little DNA virus with dual atom form due to which it is termed as geminivirus. TYLCV is the lone virus which is transmitted through whitefly holding genome with merely individual round DNA constituent, while all others have dual constituent DNA genome. Due to its genome construction, this virus is given different names. Tomato Golden Mosaic Virus ( TGMV ) in South America. In Florida as Tomato Mottle Virus ( TMoV ) which is transmitted by Ag foliage whitefly Bemisia argentifolii ( Cohen et al. , 1994 ) while in Australia and India it was referred as TLCV, Tomato Leaf Curl Virus. In US TYLCV has been established in Florida and besides been found in Georgia, Louisiana, North Carolina, Texas and Arizona.

These all viruses have different symptoms on tomato ( Green and Kallo, 1994 ) including different nucleotide construction and sequences. TYLCV symptoms do non look instantly after the infection of virus on tomato. It can take two hebdomads to look the symptoms after the virus vaccination. Plant become leathery with borders xanthous and besides curve upward ( Fig. 1 ) . The initial fruit loss and dropping of flowers are the general symptoms of the septic workss. Tomato works becomes stunted and could easy be observed ( Fig. 2 ) . The earlier infection consequences in more loss of production.

Fig.1.jpgFig. 2.jpg

Fig. 1 Fig. 2

Tomato Yellow Leaf Curl Virus ( TYLCV ) is one of the most of import and sever disease which have a important consequence on tomato production ( Abdel-saleem, 1999 ) . This disease has a major economic impact, doing a diminution in the income of the manufacturers and agriculturists and finally higher monetary values for consumers. Presently 125 million dozenss of tomatoes are being produced worldwide of which china the chief manufacturer is accounting about one-fourth of the planetary production ( FAS, 2009 ) . TYLCV has a important figure of host scope but Tomato served as a major host works for this disease. Some other of import hosts for this disease include spider vine ( Boehavia erecta ) , beans ( Phaseolus vulgaris ) , tick weed ( Cleome viscose ) and knot weed ( Polygonum spp. )

Biotype B of Bemisia tabaci serves as a vector for this disease ( Mehta et al. , 1994 ) . The silvering of squashes caused by the Bemisia was observed every bit early as 1963 ( Baery and Kapoller, 1963 ) and a really broad scope of this insect indicate that Biotype B has been present in this part for a long clip. The strength of the transmittal is really high but this disease can be transferred in seed or dirt ( McGrath and Harrison, 1995 ) . Due to piercing and sucking oral cavity parts, the acquisition clip of this virus is between 20 to 60 proceedingss and vaccination eating clip ranges from 10 to 30 proceedingss with a continuity period of by and large 10 to 12 yearss. High temperatures with less or no rain, whiteflies, weeds and septic grafts are the factors that favor the development of TYLCV. This virus develops with in workss in bast for which symptoms appear after about 15 yearss of vaccination ( Ber et al. , 1990 ) . Bemisia whitefly can give up to 15 coevalss per twelvemonth in Jordan vale due to favourable environmental conditions in that country and economic loss to vegetable harvests due to Bemisia tabaci in Israel was confirmed in 1931 ( Avidov, 1944 ) . Though the nymphal phases of Ag foliage whitefly have the capableness to get the TYLCV from the septic workss but merely the grownups are involved in the transmittal of virus disease in harvests.

This disease, TYLCV is soundless slayer and this is one of the factors for impacting the production and quality of tomato in the universe. This really of import harvest though has really low output in tropical and semitropical countries in comparing with temperate countries. The mean production of tomato during the twelvemonth 1980 was estimated to be 55 tons/ha for USA, 52 dozenss for Japan, 9 dozenss and 10 tons/ha for Philippines and Thailand consecutively ( Jones et al. , 1993 ) . TYLCV is a confining factor in tomato production due to loss of tomato works in early phase of infection by this virus.

TYLCV causes terrible stunting in workss. Besides the downward cup shaped signifier of foliages immediate after infection, leaves form becomes unnatural subsequently. Upward motion of the foliage borders is besides observed. Vector opposition to insecticide may happen, when insect powder are used to cut down the onslaught of Bemisia tabaci, a vector for TYLCV. Irrespective of the insect powder intervention, there are certain other methods to stamp down the population of Bemisia tabaci and finally the onslaught of TYLCV. This method includes cultural patterns ; seedling seting day of the months can be adjusted when the population of whitefly is high both in green house and unfastened Fieldss ( FAO, 1998 ) . Due to fact that the control and direction of TYLCV is expensive and have limited options, tradional methods of commanding vector is being used ( Cohen and Anderson, 1994 ) by insecticides interventions. But these methods have certain restrictions due to the development of opposition in vector against the pesticide which finally consequences in the risky environmental effects ( Palumbo et al, 2001 ) . Furthermore insect powder are merely the solution when there is a opportunity of excessively high vector population. Other methods which are used to command TYLCV are physical barriers and screens, which could ensue in extra production cost and jobs of shading, excessively much heat and high humidness severally. So it is best suggested genteelness harvests which are immune or tolerant to TYLCV so that the output losingss due to this virus can be reduced.

Zhenxing in 1999 conducted an experiment choosing 13 TYLCV immune beginnings and AVRDC genteelness lines ( Table. 1 ) . In his experiment tomato were sown in November and transplantation was done after one month of seeding with normal cultural patterns.

Rating Scale: Zhenxing rated the TYLCV with following badness graduated tables.

Light leaf yellowing

Moderate works acrobatics and leaf civilization and yellowing

Severe works acrobatics and foliage curling and yellowing

Disease index ( DI ) was calculated by following

DI= ( n1+2.n2+3.n3 ) .100/3.N

ni=is the morbid works in each class

N= Total figure of workss

The disease was rated at vegetive growing, 50 % of blossoming and fruit ripening.

The information was collected on average fruit weight, thickness and soundness, its form and soluble solid contents. In his experiment during vegetive growing T1, TYLCV was observed after 25 yearss of seting. Out of 13 assortments, four assortments started developing symptoms while staying assortments did non demo any symptom. In T2 of 50 % flowering phase one more assortment showed symptom. Similarly in T3 of fruit ripening phase after 65 yearss of transfering disease index ranged from 0 % to 60 % with the cheque cultivar with 10.7 % index. Out of 13 assortments, nine assortments showed symptoms of TYLCV from T1 to T3 ( Table. 2 )

Table. 1 Screening for tomato xanthous foliage coil virus opposition beginnings.

AVRDC accession


Reported opposition

BL 937

H24 ( India )



H36 ( India )



TY52 ( Israel from Dani Zamir )



France ( Laterrot )


Avinash # 2

Novartis loanblend


FLA 438-17

Florida ( J. Scott )


FLA 456-17

Florida ( J. Scott )


FLA 582-17

Florida ( J. Scott )



Royal sluis loanblend



Hezora seed comp.


CLN 2117dcl-26-19-15

AVRDC genteelness line


TLCV ( 271/1 x 26 ) -1

Engendering line from Dr.Deshpande, IIDR, India


CL 5915-93D4-1-03

Susceptible cheque


Table. 2 Tomato TYLV disease index and fruit features


Disease Index

Fruit features




Thickness ( centimeter )

Firmness ( g/cm2

Soluble solids ( % )

Mean fruit wt ( g )

Shape index ( length/width )

BL 937































Avinash # 2









FLA 438-17









FLA 456-17









FLA 582-17



























CLN 2117dcl-26-19-15









TLCV ( 271/1 x 26 ) -1









CL 5915-93D4-1-03









Asiatic Regional Centre-AVRDC, Report 1999.

Scale development and showing to measure the TYLCV

The remotion or control of vector is non the solution of TYLCV, as vector opposition against these insect powders develops in Bemisia tabaci. So in malice of this, it is best to develop/or strain immune tomato cultivars to avoid TYLCV ( Morrales, 2001 ) . In this method cistrons from the wild immune tomato are transferred to field cultivated tomatoes because at earlier, these wild species were screened for opposition against TYLCV.

As we compare the controlled green house vaccination with self-generated field vaccination, it ‘s non dependable to concentrate merely on self-generated vaccination because many of the field workss may get away infection even under heavy vaccination ( Vidavsky et al. , 1998 ) . It could be misdirecting if we select the susceptible workss during testing as resistant which were really escaped while vaccination and therefore could be used for farther crosses as immune parents. So trusting merely on the symptoms while choosing the immune tomato workss could be incorrect ( Vidavsky et al. , 1998 ) .

While vaccination in green house besides have some confining factors. White fly may non inoculate a peculiar cultivar and may prefer to feed on another works merely making a job of non penchant. Waxy or thick cuticle and certain other physical barriers may lend in non penchant of white fly. ( Bellotti and Arias, 2001 ) . So single vaccination in coops may forestall the non penchant in white fly.


Mass vaccination of immature tomato seedlings. ( A ) Whiteflies instantly after set downing on

the tomato workss, prior to traveling to the dorsal side of the foliage. ( B ) Close-up on workss from A.

( C ) Inoculation entree eating of whiteflies on tomato seedlings.

Clip coops could be used while mass vaccination with big figure of population of white flies to keep the truth of white flies on foliages.


( A ) Side position of the cartridge holder coop attached to a

Tomato foliage. ( B ) Bottom position of the cartridge holder coop, demoing the caged whiteflies feeding from the tomato

Leaf dorsal side.

Lepidot et Al in 2006 developed a graduated table for the rating of TYLCV opposition degree in tomato.

In green house: They used an insect cogent evidence green house to keep the civilizations of tomato xanthous foliage coil virus isolates in tomato. Biotype B of the whiteflies were besides reared and maintained in an insect cogent evidence green house. These grownup whiteflies were so given 48 hours acquisition entree to infected TYLCV workss following with another 48 hours of vaccination to the graduated table tomatoes. Almost 50 whiteflies were released on each works to guarantee the 100 % infection at first leaf phase. Similar method was besides repeated for control and not inoculated workss with virus free whiteflies. White flies were so removed by using imidacloprid and after that workss were maintained in insect cogent evidence green house until symptoms appear. The workss were selected by perennial choice and testing methods up to 4 to 5 coevalss so that opposition for segregation ceased.


TYLC symptoms in ( A ) a tomato works infected with TYLCV, ( B ) a tomato field. TYLC, ( C ) a banana Piper nigrum works infected with TYLCV, ( D ) a banana Piper nigrum field. TYLC, ( E ) Datura stromonium ( F ) common bean ( Phaseolus vulgaris curriculum vitae. Topcrop ) infected with TYLCV.

Symptoms badness Scale: Friedmann et Al in 1998 described following symptom badness graduated table ( Fig. 3 )

0= no seeable symptoms, same symptoms for inoculated and non inoculated workss

1= really little yellowing of cusp borders on apical foliage

2=some yellowing and minor curling of cusp terminals

3= a broad scope of foliage yellowing, curving and cupping with some decreases in size

4= really terrible works acrobatics and yellowing, pronounced leaf cupping and curling and works growing Michigans.

Plant tallness is given as the per centum of control workss height that the inoculated intervention achieved e.g. tallness of the inoculated plant/height of the un-inoculated works * 100


Fig. 3 TYLCV disease badness index

In field: In their experiment after the controlled green house vaccination, they transplanted the workss in field. They treated the workss with imidacloprid before organ transplant in the field. Ten braces of rows of indiscriminately distributed were planted. Each brace of rows was planted with one inoculated and one control comprising of five workss in a individual row. The within rows distance was 0.5 m while between rows it was 1.2 m. imidacloprid was used 4-8 hebdomads after organ transplant before roll uping the information. During first and 2nd harvest all mature and ruddy fruits were harvested while in the 3rd harvest all mature red and immature viridity were collected to cipher the mean output, fruit weight and figure of fruits. Statistical analysis was done by one manner ANOVA trial ( SAS Institute, Cary, NC ) .


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