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Doctoral thesis2024Open access

Enhancing spruce defence against an insect pest : effects of somatic embryogenesis and methyl jasmonate treatment

Berggren Nieto, Kristina


Enhancing plant resistance against pests has the potential to become a sustainable alternative within forestry. Exogenous application of the plant defence signalling hormone methyl jasmonate (MeJA) as well as propagation through somatic embryogenesis (SE) has been shown to increase Norway spruce (Picea abies) plant’s resistance to the major forest regeneration pest the pine weevil Hylobius abietis. The aim of this project was to investigate why SE plants display higher resistance. We explored the effects of SE alone and in combination with MeJA on Norway spruce plants’ resistance and tolerance, pine weevil behaviour, as well as the underlying mechanisms to their enhanced resistance. Our results suggest that SE and MeJA together have the potential to synergistically enhance plant resistance against weevil damage, and reduce mortality in the field for at least three growing seasons. MeJA treatment and, to a lesser extent SE alone, can influence pine weevil feeding preferences over time based on plant palatability. Moreover, emblings displayed a higher density of phloem constitutive resin ducts, which may contribute to explain their increased resistance. MeJA-treated emblings formed both fewer and smaller traumatic resin ducts than treated seedlings, implying traumatic ducts do not play a large role in the greater resistance seen for MeJA-treated emblings. Finally, SE and MeJA displayed opposing effects on the onset of wound healing and healing rate; MeJA accelerated onset but decreased overall healing rate, and vice versa for emblings. In conclusion, SE plants appear to be differentially palatable to the pine weevil, and exhibit defensive responses different from seedlings, both in how they resist and recover from damage. These findings increase the understanding of plant stress responses, defence traits and pest behaviour, and offer a sustainable approach to plant protection, encouraging the use of our results in practical applications.


emblings; forestry; Hylobius abietis; induced defence; Norway spruce; Picea abies; pine weevil; plant; resistance; plant tolerance; regeneration pest

Published in

Acta Universitatis Agriculturae Sueciae
2024, number: 2024:40ISBN: 978-91-8046-344-7, eISBN: 978-91-8046-345-4
Publisher: Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Forest Science

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