Some wild species germinate much slower than cultivated species. It is unknown if this is caused by seed dormancy.
Before sowing, seeds are disinfected with Na3PO4 to avoid infection with Tobacco Mosaic Virus (TMV) and other tobamo viruses.
Seeds are sown in seed trays with a soil mixture at 25-30°C, generally in January, but it is possible to sow between October and May. After 14 to 30 days the seedlings are transplanted to Rockwool blocks and placed in a glasshouse nursery on tablets, at a temperature of 23/20°C day/night and additional light.
About nine weeks after sowing, the plants in the Rockwool blocks are placed on Rockwool bags at a distance of 50 cm in the row and 100 cm between the rows. The distance between rows can differ due to the substrate system used. The temperature in the greenhouse is kept at 23/20°C day/night. The plants are grown along wires. Per plant two stems are maintained (indeterminate types). Plants are pruned once a week. Precautions are taken to prevent virus transmission. The plants are grown in a glasshouse free of pollinating insects. Consequently, it is not necessary to bag the flowers to avoid cross pollination. To enhance pollination in order to improve seed set, the flowers are touched with a trembling device weekly.
Per accession generally 7 plants are used for regeneration. In case of heterogenic accessions, accessions producing few seeds or wild species, up to 14 plants are used. The number of plants per accession is limited due to the high input in labour and capital.
About six months after sowing the fruits are ripe but large variation exists between accessions in flowering time, fruit set and seed production. Per plant 3 to 10 fruits are harvested, depending on the number of seeds per fruit. Fruits are harvested in several rounds when they are ripe and stored for at least a week before seed extraction.
Pest and disease control
- Spider mites with Phytoseiulus persimilis
- Thrips with Phytoseiulus persimilis and Orius laevigatus
- White fly with Aphidus coleman
- Aphids with Encarcia formosa
- Spider mites, in case biological control is not effective
During regeneration the plants are checked visually for diseases by the Dutch Plant Health Service. In case of doubt the plants are tested to determine the disease. Infected plants are removed.