Citrus Tristeza Virus

Question 0

Characteristics

Answer 0

Long flexuous virions
2 coat proteins- CP: major coat protein-genomic RNA
CPm: minor coat protein- encapsitdation of genome 5’

Question 1

Family and genus

Answer 1

Closteroviridae

Closterovirus

Question 2

Genome

Answer 2

SsRNA

12ORF

Question 3

Symptoms on sour orange(citrus aurantium)

Answer 3

Stunting,stempitting of grapefruit
Poor yield
Seeling yellows
Vein corking
Stem pitting
Leaf fleck

Question 4

Host range

Answer 4

Only phloem ass cells

Question 5

Transmitted

Answer 5

Aphids

Question 6

Genotypes

Answer 6

T3
VT
T30
T68
T36
RB

Question 7

Recomendation

Answer 7

Inarch tolerant rootstocks

Graft,fix,water

Question 8

CTV control in SA

Answer 8

Certification scheme
Shoot tip grafting: meristem bud grow,micrograft on virus free rootstock

Becomes virus free nucleur material,kept nucleur block.indexed- free virus

Question 9

Aphid transmitted- semi persistent

Answer 9

Aphids: motile,fly,travel long distances,reach high nrs

Infection of virus free certified material in field conditions- rapid

Question 10

Sure virus free

Answer 10

Graft onto mild strain CTv

Pre immunize rootstock

Question 11

CTv mild strain cross protection

Answer 11

Not viable citrus without it

Kept globally competitive& sustained SA industry

Question 12

CTV mild strain protection breakdown

Answer 12

Grapefruit problem
Croos protected
Severe symptoms

Question 13

Mild strain cross protection problems

Answer 13

Protector strain still induce some disease
Huper infected with 2nd virus- disease more severe that virus alone
Death of whole groves- CTV and tymovirus

Question 14

Cross protection breakdown

Answer 14

Protector strain- mix containing severe component(mutation,contamination,hyper infection)

Hyper infection- more fit- severe vector transmitted challenge strain is established

Question 15

Folimonova

Answer 15

Relationships between genotypes of CTV in terms of ability to prevent super infection by another isolate of virus studied

Question 16

Pic genome

Answer 16

Ctv

Question 17

Madam vinous inoculated 13CTV

Answer 17

Virus superinfect ability determined by visual observation of GFP fluoresence in phloem ass cells

Question 18

Foliminova means

Answer 18

For all genotypes circulating in SA we need to obtain pure,mild sources to pre immunize citrus

• determine CTV genotypes in SA
• isolate them in pure form
• assess their pathogenicity
• test ability to cross protect severe forms of the genotype