ARS | Publication request: Molecular analyses revealed genetic complexity in Citrus tristeza virus Dekopon isolate and its aphid-transmitted progeny

Submitted to: Journal of Plant Pathology
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2007
Publication Date: August 24, 2008
Citation: Yokomi, R.K., Saponari,, M., Weng,, Z., Xiong,, Z. 2008. Molecular analyses revealed genetic complexity in Citrus tristeza virus Dekopon isolate and its aphid-transmitted progeny [abstract]. Journal of Plant Pathology 90(2, Suppl.),S2.314.

Technical Abstract: An assessment was made of the disease potential of a Citrus tristeza virus (CTV) isolate designated Dekopon found in a hybrid mandarin variety topworked in a citrus planting in Fresno County, CA. After aphid transmissions (AT), parental and AT isolates were analyzed by SSCP, genotyping with multiple molecular markers in RT-PCR, and sequencing of the major CP and p33 ORFs. These analyses together revealed a complex CTV population comprised of a VT-like genotype, a distinct genotype (DK) in a VT superclade, and a genotype related to but genetically distinct from T30. Segregation of genotypes from this CTV complex was observed in the AT progeny isolates. AT isolates with the VT-like and DK genotypes induced seedling yellows and stem pitting reactions which were generally more severe than the parental isolate; whereas AT isolates with the T30-like genotype produced no or mild symptoms alone. This suggested that symptoms were ameliorated by the T30-like genotype even though the DK genotype associated with strong seedling yellows symptoms was the predominant population in the parent (91% of the CP-recombinant clones). Genomic sequences of the AT progeny isolates containing a predominant single genotype were obtained from a genome-wide analysis with a CTV resequencing microarray. Phylogenetic analysis of the genomic and p33 ORF sequences suggested that the DK genotype in the Dekopon isolate are closely related to SY568 and the NUagA isolates. The resequencing analysis achieved call rates of 95.8% to 99.8% and call accuracies of 98.4% and 99.6%, and is being used to further characterize the AT isolates.