Identifying the optimum pretreatment duration and germination temperature for Abies nordmanniana [(Steven) Spach] seed, and assessing the effect of moisture content and storage temperature on seed longevity

Abies nordmanniana has recently acquired significant popularity across Europe as a high quality Christmas tree. However, commercially available seed is relatively scarce and often poor quality. The cause(s) of low germination percentage in this species are currently unknown, but may be due to a combination of inherently low viability, unreliable seed test methods, unexpectedly rapid seed deterioration, ineffective dormancy breakage pretreatments or extreme sensitivity to germination conditions. One good quality seedlot (66% germination capacity) was prechilled for 0, 3, 6, 12, 24 and 48 weeks (w) and then germinated over a range of constant temperatures (10, 15, 20, 25, 30, 35, 40 degrees C) and an alternating 20/30 degrees C (the current ISTA germination regime). A 6w prechill followed by 20 degrees C for 28 days (d) was one of the best combinations of prechill period, germination temperature and incubation duration and is therefore recommended for adoption by the ISTA. 6-12w prechilling may be preferable for plant production purposes, especially when sowing early into cooler seedbeds (10-15 degrees C). A second good quality seedlot (75% germination capacity) was stored at 10, 13 and 15 % moisture content (fresh weight basis), factorially combined with 5, 15 and 25 degrees C for up to 104 weeks. Seed deterioration was very rapid in comparison to data published for most other conifers (especially pines and spruces). At 15 and 25 degrees C seed was almost completely dead within 16w, and even at the lowest temperature (5 OC) germination capacity had virtually halved within 32w. These results demonstrate the rapid death rate of dry stored seeds of Abies nordmanniana and why even the shortest temporary storage at ambient temperatures should be avoided.