How to Capture Thousands of Genotypes-Initiation of Somatic Embryogenesis in Norway Spruce

Somatic embryogenesis (SE) is considered the most effective method for vegetative propagation of Norway spruce (Picea abies L. Karst). When the aim is commercial production, the process needs scaling up. This includes many initiations to increase the number of available genotypes in the cryo-bank. Numerous genotypes are needed to maintain genetic diversity in reforestation and, at the same time, are a prerequisite for the efficient improvement of breeding traits. Norway spruce is also highly susceptible to Heterobasidion root rot. We analysed the data from the SE initiations of Norway spruce from six different years, including a total of 126 families and almost 13,000 initiations, and used several genetic (including allele PaLAR3B improving Heterobasidion resistance), environmental, and operational variables to explain the initiation success and the number of cryopreserved embryogenic tissue (ET). Overall, the cone collection date was the best and most comprehensive single variable for predicting the initiation success and the number of cryopreserved ET in the logistic regression models. PaLAR3B allele did not interfere with SE initiation or the cryopreservation. In the optimal scenario, according to the current data, Norway spruce cones would be collected in southern Finland during the first two weeks of July (in approximately 800 d.d. accumulation) from the seed orchard or greenhouse and delivered quickly to the laboratory, and the cones would be cold-stored for five days or less before initiations on mLM media. Lower initiation frequencies in some families can be compensated by increasing the number of explants-however, taking operational limitations into account.

Automated summary

Somatic embryogenesis is the most effective method for propagating Norway spruce, and the initiation success and cryopreservation are influenced by the cone collection date. The PaLAR3B allele does not interfere with the process. Ideally, Norway spruce cones should be collected in southern Finland in early July and cold-stored for five days or less before initiation.