THE PRODUCTION OF VIRUS-FREE NARCISSUS STOCKS IN SCOTLAND

1. Virus-tested mother plants of cultivars approved by the Scottish Nuclear Stocks Association (Flower Bulbs) Ltd, and obtained by selection or therapy.
2. A rapid propagation method, namely twin-scaling.

   In practice the propagation scheme has 3 stages: 2 cycles of twin-scale propagation followed by natural multiplication in the field. During propagation clones are kept separate to allow clonal selection. The 2nd stage of propagation (second cycle of twin-scaling) is completed 7 years after twin-scaling the mother plant, and produces about 5 000 bulbs per clone for field propagation. The scheme presently has an annual input of 4 clones and the first batch of bulbs (22 000) entered the 3rd stage of propagation in 1979. The agronomic quality of the clones will be assessed during the 3rd stage of propagation.

3. A system for protecting virus-tested plants from infection.

Protection from nematode-transmitted and aphid-transmitted viruses is provided by growing plants in vector-proof houses in the first two stages, and includes isolation and soil fumigation during propagation in the field.

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