title: Genotype composition of populations of grapefruit-cross-protecting citrus tristeza virus strain GFMS12 in different host plants and aphid-transmitted sub-isolates.
abstract: Citrus tristeza virus (CTV) causes severe losses in grapefruit production in South Africa and requires mild-strain cross-protection to maintain production. Unfortunately, cross-protection breakdown of the pre-immunizing CTV grapefruit mild source GFMS12 is prevalent in grapefruit in South Africa. The CTV genotype composition of the GFMS12 population inoculated onto different hosts was determined by sequencing part of ORF1a and the p23 gene of multiple clones from each plant. Analysis of the GFMS12 population in Mexican lime and Marsh and Star Ruby grapefruit varieties revealed that at least four genotypes occur in the GFMS12 population and that genotype compositions differed amongst the populations in different host plants. Single-aphid-transmitted sub-isolates derived from the GFMS12 mother population on Mexican lime appeared to contain three populations of a mixture of VT-like and recombinant B165/VT-like genotypes; a mixture of recombinant RB/VT- and B165/VT-like genotypes; and a single recombinant B165/VT-like genotype. This study underlines the importance of determining the genotype composition of a potential CTV pre-immunizing source on a range of inoculated host species before utilization.
authors.affiliation: Department of Microbiology and Plant Pathology and FABI, University of Pretoria/Citrus Research International, New Agricultural Building, Lunnon Road, Hatfield 0002, South Africa. ScottKA@arc.agric.za
authors.forename: Katherine Anne
authors.initials: KA
authors.lastname: Scott
authors.forename: Quinsile
authors.initials: Q
authors.lastname: Hlela
authors.forename: Olivier
authors.initials: O
authors.lastname: Zablocki
authors.forename: David
authors.initials: D
authors.lastname: Read
authors.forename: Stephanus
authors.initials: S
authors.lastname: van Vuuren
authors.forename: Gerhard
authors.initials: G
authors.lastname: Pietersen
mesh_terms: D000818:Animals; D001042:Aphids / Q000821:virology*; D002957:Citrus / Q000821:virology*; D032083:Citrus paradisi / Q000821:virology*; D017790:Closterovirus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification* / Q000502:physiology; D005838:Genotype; D058507:Host Specificity; D007303:Insect Vectors / Q000821:virology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000821:virology*; D013019:South Africa; D014764:Viral Proteins / Q000235:genetics
chemical_list: D014764:Viral Proteins