Pollination and seed set in vinca [Catharanthus roseus (L.) G. Don]

Pollination of vinca [Catharanthus roseus (L.) G. Don] 'Parasol' and 'Cooler Peppermint' was investigated to improve commercial seed production. The flower was functionally close to cleistogamous with pollination limited by the foraging behaviour of insects. Only probosces of butterflies and hawkmoths could reach the anthers and stigmas. The pollen and stigmas were sticky, with autonomous self-pollination occurring from day -1 to day 0 (anthesis) when the pistils and corolla tubes elongated. Seventy percent of pollen germinated on the stigma at anthesis, with less germination at 35degreesC than at lower temperatures. Flowers lived 4-5 d after anthesis, but were functional for only a few days. Only the probosces of butterflies or hawkmoths reached the stigmas and pollen, with bees and droneflies absent. More than 30% of flowers set seed by autonomous self-pollination, with pollinators greatly increasing fruit set and the number of seeds per fruit. In 'Cooler Peppermint', fruit set in open pollination was 95%, while it was 38% in plants covered with net. Thus, reproduction in vinca is largely dependent on pollinators which are agricultural pests. Promotion of autonomous self-pollination is important for commercial seed production.