RESISTANCE TO TAMARILLO MOSAIC VIRUS IN TRANSGENIC TAMARILLOS AND EXPRESSION OF THE TRANSGENES IN F1 PROGENY

The most serious disease affecting tamarillos (Cyphomandra betacea (Cav.) Sendt.) in New Zealand is tamarillo mosaic potyvirus (TaMV). In an attempt to induce resistance to TaMV, we have inserted a number of transgenes based on the TaMV coat protein into tamarillo leaf sections using Agrobacterium tumefaciens LBA4404. Shoots were regenerated and rooted in the presence of kanamycin and the resulting plants were inoculated with TaMV. We recorded the severity of symptoms and the seasonal appearance and disappearance of symptoms on plants growing in a containment screenhouse.

We identified several lines which showed milder symptoms at temperatures of 20°C or lower.
In these lines the symptoms disappeared earlier in spring and reappeared later in autumn compared with transgenic control plants.
In some other transgenic lines, symptoms were more pronounced than in non-transgenic control plants.
Fruit on the lines with mild leaf mosaic had no virus symptoms, whereas mosaic blotching was present on non-transgenic fruit and fruit from transgenic lines with severe leaf symptoms.

Seedlings grown from transgenic and control fruit were inoculated with TaMV and the proportion of plants without symptoms was recorded.
Some of the seedlings which initially displayed virus symptoms later recovered.
This suggests that a gene silencing mechanism has been induced.
A field trial of the most resistant transgenic lines has been established.

XXV International Horticultural Congress, Part 11: Application of Biotechnology and Molecular Biology and Breeding – Gene Expression and Molecular Breeding, Genome Analysis.

D. Cohen, R.C. van den Brink, R.M. MacDiarmid, D.L. Beck, R.L.S. Forster

https://doi.org/10.17660/ActaHortic.2000.521.2