Genotype variation of citrus tristeza virus after passage on different hosts, and changes in the virus genotype populations by the vector Aphis gossypii

Abstract

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.

Complete genome sequencing and characterization of a potential new genotype of Citrus tristeza virus in Iran

“…Our study of the potential variation of the virus in citrus trees revealed that the Sari isolate of CTV had mild variation, which could contribute to the virus’s best fit in different environmental conditions. This potential variation has also been reported in previous studies [ 31 , 32 ], which suggests that it could be a fitness tool for the virus. Our findings add to this body of research and provide new insights into the potential for CTV to adapt to different host environments.…”

“…Previous studies have shown that the CTV genotypes can be changed after passage through different hosts [ 31 ]. Studies demonstrated the existence of genotype population modification in the genotype of a single isolate after passage through two different hosts, demonstrating that the presence and dominance of population genotypes were modified by virus transmission from sweet orange to Mexican lime [ 31 , 32 ]. So, CTV has a variation potential in a population in a host which our results confirm previous studies and these variations can support CTV for best fit in a different situation.…”

Diagnostic Efficiency of CTV and HSVd for Early and Mixed Infections Using Bioamplification in Citrus Arizona 861-S1 and RT‒PCR Compared to Direct RT‒PCR

“…Nonetheless, detecting both pathogens via RT-PCR was only possible after eight months of incubation. In the case of CTV, although CTV isolates naturally correspond to mixed populations of the virus, according to Camps et al [21], they used a VT-type isolate, classified as aggressive because it reacts to the MCA13 antibody [17], and were able to observe vein clearing in the leaves of Arizona citron 861-S1-inoculated plants. In this study, 334 isolates from Mexican lime were obtained initially from a sweet orange in the Pica locality and were classified as VT-type or MCA13-positive [13].…”

“…In a study carried out by Pizarro [16], at the Mallarauco locality close, it was determined that the cachexia incidence in this area varied between 10.3 and 36.7%; this area of the country was considered the most affected by this disease [15]. Although the reports by Weathers and collaborators were based on the symptoms observed in the field and with Mexican lima indicator plants, most modern reports have also used serological and/or molecular methods to diagnose the presence of these pathogens, especially CTV and cachexia isolates [12,13,16,17].…”

“…The primary means of spreading these diseases is through grafting, although tristeza is also spread by aphids. In Chile, a study carried out by Camps et al [17] demonstrated that Aphis gossypii was capable of transmitting the virus from infected plants to healthy plants, producing a change in the characteristics of the virus populations, where the attenuated populations acquired by aphids after being transmitted to a new host (from Mexican lime to sweet orange) became populations where an aggressive variant predominated. On the other hand, the causal agent of cachexia, Hop stunt viroid (HSVd), can be transmitted highly efficiently through contaminated cutting tools.…”