Virus Infections Reduce in vitro Multiplication of 'Malling Landmark' Raspberry

Virus-infected plants are often symptomless and may be inadvertently used as explant sources in tissue culture research. Our objective was to determine the effect of virus infection on micropropagation. We studied the effects of single and multiple infections of three common raspberry viruses on the in vitro culture of 'Mailing Landmark' red raspberry (Rubus idaeus L.). Virus-infected raspberry plants were produced by leaf-graft inoculation from known-infected plants onto virus-free 'Mailing Landmark'. Single-virus source plants were infected with either tobacco streak ilarvirus (TSV), tomato ringspot nepovirus (TomRSV), or raspberry bushy dwarf idaeovirus (RBDV) and were free of other viruses as determined by enzyme-linked immunosorbent assay (ELISA) and bioassay. Virus-free, single, and multiple virus-infected 'Mailing Landmark' explants were initiated into culture and multiplied on Anderson's medium with$8.9 \mu M$ $N^6-benzyladenine$(BA). At the end of the multiplication tests, ELISA reconfirmed virus infections. In vitro multiplication of 'Mailing Landmark' was significantly reduced by multiple infections, and multiplication of plants infected with all three viruses (RBDV + TomRSV + TSV) was less than half that of virus-free cultures. Shoot height and morphology of in vitro cultures were not influenced by virus infection. The greenhouse stock plant with the three-virus infection was stunted and yellow compared to the control and the other infected plants.