Epigenetic memory effects in Norway spruce: are they present after the age of two years?

ABSTRACT

Short-term trials on cultivated soil were planted with families of Norway spruce that had shown epigenetic memory effects in early tests up to age two years. Measurements and assessments were made of phenology traits, tree heights and stem defects until age 16 years in these trials. The memory effects of the temperature conditions during embryo development and seed maturation were confirmed for the timing of bud flush and for start and cessation of shoot elongation at age six years. The mean differences in timing of these events caused by temperature treatments were on average less than two days. They were considerably larger for families with strong effects on terminal bud set at the end of the first growing season. The memory effects did not result in a prolonged shoot growth period, nor did they affect height growth. Interaction effects expressed in adaptive traits between factorial treatments of temperature and daylength during seed production were large in the short-term trial and were still present at age nine years. The results presented demonstrate that strong memory effects observed in early tests may also be expressed in phenology traits for at least the next five growing seasons.

KEYWORDS:

• Picea abies
• epigenetic memory effects
• short-term tests
• phenology
• height growth

Acknowledgement

Many colleges at the former Norwegian Forest Research Institute, now Norwegian Institute of Bioeconomy Research (NIBIO), and at Biri Nursery and Seed Improvement Centre have participated in the activities related to the trials reported here. They are all thanked for their contributions. Thanks are due in particular to Øystein Johnsen, who planned many of the experiments, to Arne Steffenrem for providing the figures and to him and Dario Isidro Ojeda Alayon for comments to earlier versions of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Several of the early tests were supported by the EU Grant QLK5-CT-2000-00349. Measurements made in the short-term trials were supported by NIBIO and the analyses and writing of this report by The Research Council of Norway Grant no 297294 and the project B4EST of the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No 773383.