Optimising storage and in vitro germination of Eucalyptus pollen

Abstract

The best sucrose solution for maximum in vitro germination of Eucalyptus pollen was investigated in order to evaluate pollen germination rate as an indicator of pollen viability. In vitro germination of both freshly collected and 1-year-old pollen (stored at 4°C) of Eucalyptus grandis, E. smithii, E. nitens, E. dunnii and E. macarthurii was carried out in 0, 10, 20, 30, 40 and 50% (w/v) sucrose solutions, either with (0.15 mg L–1) or without boric acid. Similar trends were obtained for both fresh and 1-year-old pollen, with all species responding most favourably to 30% (w/v) sucrose and 0.15 mg L–1 boric acid. When an optimal in vitro germination medium had been established, the viabilities (%germination) of E. smithii, E. nitens and E. grandis pollen, stored at room (25°C), fridge (4°C), freezer (–10°C) and liquid nitrogen (–196°C) temperatures, were compared. For all tested species, germination declined as storage temperature increased, and by 8 months, the highest survival was obtained with cryostored pollen.