The simultaneous use of a rapid diagnostic method with the effective cleaning of infected budwood is a powerful preventative method for controlling viral diseases. The objective of this study was the multiple detection of CTV, CEVd, and HSVd, through bio-amplification in Arizona 861-S1 citron plants, combined with two incubation temperatures and multiple RT-PCR in two steps. Citron indicator plants were inoculated with the three pathogens, both individually and simultaneously, with four un-inoculated plants as controls. After four months of incubation at the two different temperatures, both the multiple and individually inoculated plants showed symptoms associated with these pathogens, which were subsequently corroborated through the use of multiple RT-PCR in two steps. This diagnostic method could be employed as an efficient, cost-effective alternative to the methods that are currently in use for detecting CTV, CEVd and HSVd, nevertheless its effectiveness should also be evaluated with tests using different isolates of these pathogens.
Citrus tristeza virus (CTV) was reported in the 1960's to affect Meyer lemon trees in Chile, but no field symptoms were observed. This study performed a complete biological, serological and molecular characterization of one hundred CTV isolates obtained from different hosts and geographical origins. Decline symptoms (DI) were not found on trees grafted onto sour orange. In Pica Oasis in northern Chile, stem pitting (SP) was found to affect grapefruit and Mexican lime trees. Most isolates present in the central area were considered mild (MCA-13-negative), while in the northern area aggressive isolates were observed and detected. Some of these isolates were capable of causing SP on grapefruit under field and greenhouse conditions and on sweet orange under greenhouse conditions. Almost all of these isolates were MCA13-positive and had nucleotide sequences associated with the VT genotype.
Phylogenetic analyses categorize seven genotypes of citrus tristeza virus (CTV). The symptoms caused by this pathogen, their expression and severity are influenced by CTV genotypes, host species, cultivars, and infected host rootstocks. This study aimed to verify how populations of Chilean CTV isolates changed following inoculation from infected sweet orange to Mexican lime trees, and to determine if CTV genotype populations influenced transmission efficiency via Aphis gossypii. Reverse transcription polymerase chain reaction showed variation in genotypes of populations of CTV in Mexican lime, after graft inoculations using infected sweet orange chip-buds. Severe genotypes (VT) were detected after inoculation of mild isolate CTV populations (T30). The T30 donor populations also reduced transmissibility via A. gossypii; however, these results may not be conclusive due to mixture with the VT genotype. There is evidence of high rates of virus acquisition by this aphid species, but also low transmission efficiency, which may partially explain the historical absence of tristeza epidemics in Chile.
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