engleski

Influence of grapevine phenological stage and virus inoculum composition on the replication of GLRaV-3

Background: Grapevine performance can be impacted by more than 80 viruses and virus-like agents, with grapevine leafroll-associated virus 3 (GLRaV- 3), as one of the most dangerous viruses affecting grapevine performance. Mixed infections occur naturally in grapevine populations and GLRaV-3 is usually accompanied by other viruses. Impact of grapevine viruses on GLRaV-3 replication is still unknown due to lack of studies on this subject. Objectives: Relative GLRaV-3 quantification in grapevine of different phenological stages inoculated with GLRaV-3 in combination with other grapevine viruses. Materials and methods: Four different inoculums containing GLRaV-3 accompanied by different combination of other economically important grapevine viruses were inoculated by green grafting on 41 indicator plants during the summer season. Phloem tissue was collected in two different phenophases: the dormancy which occurred five months post inoculation, and the beginning of bud swelling which occurred eight months post inoculation. Total RNA was extracted using a commercial kit followed by the synthesis of cDNA. By using SYBR green qPCR, relative concentration of two genomic GLRaV-3 regions: ORF1a and CP was assessed by normalizing their Ct values with those of housekeeping genes. Results: Relative concentration of GLRaV-3 was generally higher during the dormancy stage, but did not depend on the inoculum composition. It varied significantly in the bud swelling stage where inoculum harbouring the highest number of viruses (six in total) showed significant differences in comparison to other inoculums. The GLRaV-3 concentration at this stage appears to depend more on inoculum composition and infection duration than on sampling phenophase.

GLRaV-3, relative quantification, phenophases

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