Towards Sterile Plant Production in Sturt's Desert Pea ('Swainsona formosa') via 'In Vivo' Triploid Plant Production

Sturt's Desert Pea, 'Swainsona formosa', (G.Don) J.Thompson, is an ornamental legume native to Australia. The economic importance of this plant is in its use as a hanging basket or container plant or for cut flowers. The production of large amounts of pollen grains in the flower is a major impediment to the commercialisation of this plant. Petal staining by pollen, as well as self-pollination during transport, reduces the quality of the flowers. The objective of current work is to produce triploid plants using colchicine, an anti mitotic chemical. Sturt's Desert Pea seeds were treated with 0.1% colchicine for 0 (untreated), 4, 8 and 12 hours. The seeds were then transferred to distilled water for a further total treatment time of up to 24 hours. After seed germination on moist filter paper in Petri dishes and early seedling development in Jiffy® pots, the seedlings were transferred into 20cm pots containing a pasteurised mixture of sand and peat (3:1) in a glasshouse at a temperature of 25-32°C, with a 16 hour photoperiod. These plants produced flowers within 80 days. The chromosome number of flowers was ascertained in squashed pollen mother cells obtained from approximately 1.3 cm long flower buds, and stained with 1% aceto-orcein. The results indicate that the chromosome number of untreated plants was n=8. The flowers of colchicine treated plants were emasculated at 14-16 days after floral initiation and were then pollinated with pollen from untreated plants. At the same time, untreated plants were also crossed with each other. Seeds were collected from these crosses within 40-45 days. The results indicated that the increase in soaking time reduced the number of germinated seeds, although this was not significant. However, the duration of colchicine treatment significantly affected radicle length, microspore size and peduncle length, but not petal length. Furthermore, no chromosome doubling was observed at any length of soaking time.