engleski

Plum pox virus strains of stone fruit species in Croatia

Plum pox virus (PPV) is the most devastating virus of stone fruits. It encompasses seven strains with different biological features of which PPV-M (Marcus), PPV-D (Dideron), PPV-C (Cherry), PPV-EA (El Amar), PPV-W (Winona) are endowed with non-recombinant genomes whilst PPV-Rec and PPV-T are natural recombinants. The Croatian nursery stone fruit species have been routinely screened for the PPV presence by ELISA since 1988. From 2004, IC-RT-PCR has been introduced to supplement the detection methods in accordance with the EPPO protocol. Specific strain detection is enabled by IC-RT-PCR utilizing strain-specific primers whose amplification products can be further characterized after sequencing. Usually, leaf samples are taken both from asymptomatic and symptomatic plants to be tested by ELISA and IC-RT-PCR. The amplification product obtained by using PPV-M, PPV-D, PPV-Rec and PPV-C specific primers P1/PM, P1/PD, mD3/mM5 and SoC1/SoC2, respectively, resulted in amplification product of expected sizes. Additionally, the PPV-C amplicon (193 bp) was cloned into pTZ57R/T vector and inserts from ten recombinant plasmids were sequenced. So far, the PPV strains M, D, and Rec have been regularly detected in the country with the geographic prevalence of PPV-M that occurs in 10 out of 15 counties. The European plum is under the highest PPV-M infective pressure but peach and nectarine are also affected. PPV-D occurs only in 3 out of 15 Croatian counties with the highest incidence in plum and very low in peach. The natural recombinant PPV-Rec occurs in imported plum trees in the far east of the country causing severe symptoms and yield loss. It can also be found in wild plums and apricots suggesting that besides PPV-Rec variants introduced with plum planting material, there exist a population of variants diversifying in our fruit growing zones for a longer while, as suggested from their phylogenetic analyses. Indigenous Dalmatian sour cherry variety Maraska sampled in 2010. from a nursery near Zadar was found to host PPV-C. The genetic structure of this sour cherry (PPV-SoC) isolate was homogeneous. Phylogenetic analysis of specific cloned amplicons showed that Maraska PPV-SoC isolate is identical to the prototype sour cherry isolate originating from Moldavia. This, besides being the first report of PPV-C strain in Croatia and the first report of PPV in locally grown sour cherry, raises interesting questions on PPV-C origin and evolution.

Plum pox virus; Croatia; stone fruits

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