Articles
PHYTOSANITARY IMPROVEMENT OF FRUIT TREE SPECIES: DIAGNOSTIC STRATEGIES IN VIRUS-INDEXING OF IN VITRO PLANTS
The validation of disease-indexing data for in vitro material in certification schemes would allow greater exploitation of the role of in vitro techniques in the production of disease-free planting stocks.
Rapid progress in the development of highly sensitive laboratory diagnostics based on the amplification of the virus genome might in future remove the need for lengthy and cumbersome progeny testing in the field for certification purposes.
Many of the fruit tree viruses are able to survive in in vitro cultures unless a suitable elimination treatment is applied.
However, success rates in elimination of different viruses show high variation depending on the method applied, on the plant species and even cultivar, the virus and the type of infection (single or mixed) involved (Knapp et al., 1997a,b).
A major part of work in sanitation programs concerns the selection of virus-free plants.
In the last few years we focused on parameters, which had a major impact on reliability of disease-indexing in vitro. We found that in vitro culture growth phases induced fluctuations in virus accumulation.
We investigated the effects of different elimination treatments on virus suppression.
We achieved optimization in sampling of in vitro plants through investigation of virus distribution patterns.
Finally, we compared results from different diagnostic methods such as ELISA using commercially available serodiagnostics were used in DAS or Two-Step ELISA, immuno-tissue printing and PCR (Knapp et al., 1995c, 1997 a,b).