Seed coat removal greatly enhances Grevillea (Proteaceae) seed germination

Grevillea belongs to the family Proteaceae and it is a genus endemic to Australasia. The plants in the genus are valuable, both for environmental conservation and for the ornamental industry. Screening hybrid populations to select phosphate-insensitive and Phytophthora cinnamomi-resistant varieties is an effective approach to protect Grevillea plants against Phytophthora dieback and to maintain their genetic diversity. A quick and efficient method to generate large populations from seeds is required for such a screening and breeding approach. In this study, we investigated germination of seeds collected from two popular Grevillea cultivars, ‘Misty Pink’ and ‘Moonlight’. Four treatments, i.e., seed-coat removal (decoating), smoke, heat shock, and different incubation temperatures, were used in this experiment. Seed germination was recorded for up to 40 days. The results demonstrated a significant increase in seed germination by decoating (F=867.30, p<0.01), smoke (F=46.24, p<0.01), and alternating incubation temperature of 10°C/30°C (F=42.63, P<0.01). Germination responses to heat shock were not significant. The single factor of decoating resulted in a germination rate of 100%, compared with only 25.6% for intact seeds. Smoke resulted in a germination rate of 51% compared with 36% for the non-smoke treat¬ment. Seed-coat removal also considerably shortened the period from sowing to germination. Decoated seeds started to germinate four days after sowing, and the germination rate reached 94% on the 11th day, whereas intact seeds showed no sign of germination until the 15th day after sowing. This result indicates that decoating is a quick and effective method to germinate Grevillea. The major finding from this study is being tested with a wider range of Grevillea species.