Seed quality attributes in seedling production of Norway spruce (Picea abies (L.) Karst.)

Abstract

The artificial regeneration of Norway spruce (Picea abies (L.) Karst.) in the Nordic countries relies on planting containerized seedlings originating from seeds collected from either seed orchards or forest stands. The aim of this thesis is to investigate the effect of seed quality attributes on seedling production and to study whether it is possible to enhance germinability and seedling health through seed soaking treatments. The variation in seed quality among individual trees and clones and the components of seed weight variance are also studied. Commercial seed lots were screened for microbes and the effect of soaking treatment on microbial abundance was analyzed. The three seed lots contained some pathogenic fungi, but most fungi found were saprophytic. The seed lots differed in their likelihood to suffer from damping-off when germinated in water agar medium but not in peat. With current production methods seed-borne fungi do not have a great impact for seedling health, but altering for example the growing media may increase their importance. Seedling quality declined with increasing emergence time in an experiment on 1-yearold seedlings in the nursery, thus emphasizing the importance of fast germination. Seed soak-sorting hastened the emergence and increased seedling size more in 1.5-year-old containerized seedlings compared to the 1-year-old seedling crop in addition of decreasing the proportion of cull seedlings. The proportion of full seeds varied between individual trees and clones in cones collected from a forest stand and from a seed orchard. The average seed weights differed between trees or clones, but intracone variation was the greatest source of seed weight variance. This indicates that weight-based seed sorting may have a smaller impact on the genetic diversity of seed lots than previously thought. Seed and seedling producers as well as society have different preferences for seed quality attributes and different tools for quality management.