Browsing by Author "Skoric, D."
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- Biological characterization of Citrus tristeza virus monophyletic isolates with respect to p25 genePublication . Hancevic, K.; Cerni, S.; Nolasco, Gustavo; Radic, T.; Djelouah, K.; Skoric, D.Citrus tristeza virus (CTV) is the most destructive viral pathogen of citrus and displays a high level of genetic and phenotypic diversity. In this study the biological characterization of monophyletic CTV-isolates based on p25 gene (Gp 1, Gp 2, Gp 3a, Gp 4, Gp 5, Gp M) was analyzed for the first time on the set of standard indicator plants and unde r the same environmental conditions, in order to compare the phenotypic characteristics of p25 genomic variants. The results showed that tested CTV-isolates varied in their ability to induced symptoms as well as in severity of symptoms e. g. pathogenicity. (C) 2012 Elsevier Ltd. All rights reserved.
- Citrus wilsonii: Biological response to infection with different citrus tristeza virus genotypesPublication . Hancevic, K.; Cerni, S.; Nolasco, Gustavo; Radic, T.; Rosin, J.; Gatin, Z.; Skoric, D.Citrus wilsonii Tanaka is cold-resistant, rarely grown chance hybrid between Citrus ichangensis and Citrus grandis with a potential to be used as a rootstock in colder climates. In order to evaluate its reaction to Citrus tristeza virus (CTV), C. wilsonii seedlings were graft-inoculated with previously characterized CTV isolates monophyletic with respect to the p25 gene and clustering to phylogenetic groups Gp 1, Gp 2, Gp 3a, Gp 4, Gp 5 and Gp M. The evaluation of C. wilsonii symptoms and comparison with the reaction of standard citrus indicators infected with the same CTV isolates revealed that C. wilsonii infected with isolates Gp 2 and Gp 4 developed stem pitting (SP). This is in accordance with the SP-inducing potential of these CTV isolates in the standard sweet orange SP indicator. The obvious and numerous pits shown by C. wilsonii stems suggests that it reacts strongly to severe SP CTV isolates.
- East Adriatic: a reservoir region of severe Citrus tristeza virus strainsPublication . Cerni, S.; Skoric, D.; Ruscic, J.; Krajacic, M.; Papic, T.; Djelouah, K.; Nolasco, GustavoCitrus tristeza virus (CTV) represents one of the major threats to citrus production worldwide. In the East Adriatic region, CTV symptoms are mostly absent due to traditional citrus grafting on trifoliate orange (Poncirus trifoliata), a CTV-tolerant rootstock. Therefore, the virus has been continuously spreading by the propagation of infected material. The genetic variability of CTV was studied on nineteen citrus samples, collected from orchards in the coastal region of Croatia, Montenegro and Albania, that previously tested positive by ELISA and immunocapture RT-PCR. Single-strand conformation polymorphism of the amplified coat protein gene demonstrated the presence of different CTV variants in each amplicon, while sequence analysis of cloned CP gene variants confirmed their clustering into six out of the seven phylogenetic groups so far delineated. Four of these groups include sequences of severe quick decline, seedling yellows and stem-pitting (SP) isolates, thought to be found only rarely in the Mediterranean region. Regardless of the lack of symptoms in the field, CTV isolates from the East Adriatic displayed high genetic variability and pathogenic potential, additionally confirmed by biological characterisation. The high percentage of mixed infections suggest the potential for further diversification and a greater risk of severe variants spreading into new areas.
- Occurrence of stem-pitting strains of Citrus tristeza virus in CroatiaPublication . Cerni, S.; Skoric, D.; Krajacic, M.; Gatin, Z.; Santos, C.; Martins, V.; Nolasco, GustavoCitrus is grown in Croatia (approximately 1,500 ha of citrus groves) on the Dalmatian Coast and Islands between 42 and 43°30'N. The major species, Citrus unshiu Marc. (Satsuma mandarin), is grafted on trifoliate rootstock. The presence of Citrus tristeza virus (CTV) in Satsumas in the Neretva Valley Region was previously reported (3). During the course of a biomolecular characterization of isolates from Croatia, 15 budsticks were collected from field- infected, enzyme-linked immunosorbent assay (ELISA)-positive sources during the autumn of 2003 near Kaštela, Split, Metković (Neretva Valley), and on the island of Vis. Isolates were propagated by graft transmission to Madam Vinous sweet orange (SwO) and maintained in an insect-proof greenhouse at 21 to 33° C.
- Stem pitting and seedling yellows symptoms of Citrus tristeza virus infection may be determined by minor sequence variantsPublication . Cerni, S.; Ruscic, J.; Nolasco, Gustavo; Gatin, Z.; Krajacic, M.; Skoric, D.The isolates of Citrus tristeza virus (CTV), the most destructive viral pathogen of citrus, display a high level of variability. As a result of genetic bottleneck induced by the bud-inoculation of CTV-infected material, inoculated seedlings of Citrus wilsonii Tanaka displayed different symptoms. All successfully grafted plants showed severe symptoms of stem pitting and seedling yellows, while plants in which inoculated buds died displayed mild symptoms. Since complex CTV population structure was detected in the parental host, the aim of this work was to investigate how it changed after the virus transmission, and to correlate it with observed symptoms. The coat protein gene sequence of the predominant genotype was identical in parental and grafted plants and clustered to the phylogenetic group 5 encompassing severe reference isolates. In seedlings displaying severe symptoms, the low-frequency variants clustering to other phylogenetic groups were detected, as well. Indicator plants were inoculated with buds taken from unsuccessfully grafted C. wilsonii seedlings. Surprisingly, they displayed no severe symptoms despite the presence of phylogenetic group 5 genomic variants. The results suggest that the appearance of severe symptoms in this case is probably induced by a complex CTV population structure found in seedlings displaying severe symptoms, and not directly by the predominant genomic variant.