| 1. |
- Chen, Yayuan, et al.
(författare)
-
Comparing Exogenous Methods to Induce Plant-Resistance Against a Bark-Feeding Insect
- 2021
-
Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Exogenous application of the plant hormone methyl jasmonate (MeJA) can trigger induced plant defenses against herbivores, and has been shown to provide protection against insect herbivory in conifer seedlings. Other methods, such as mechanical damage to seedlings, can also induce plant defenses, yet few have been compared to MeJA and most studies lack subsequent herbivory feeding tests. We conducted two lab experiments to: (1) compare the efficacy of MeJA to mechanical damage treatments that could also induce seedling resistance, (2) examine if subsequent insect damage differs depending on the time since induction treatments occurred, and (3) assess if these induction methods affect plant growth. We compared Scots pine (Pinus sylvestris) seedlings sprayed with MeJA (10 or 15 mM) to seedlings subjected to four different mechanical bark damage treatments (two different bark wound sizes, needle-piercing damage, root damage) and previous pine weevil (Hylobius abietis) damage as a reference treatment. The seedlings were exposed to pine weevils 12 or 32 days after treatments (early and late exposure, hereafter), and resistance was measured as the amount of damage received by plants. At early exposure, seedlings treated with needle-piercing damage received significantly more subsequent pine weevil feeding damage than those treated with MeJA. Seedlings treated with MeJA and needle-piercing damage received 84% less and 250% more pine weevil feeding, respectively, relative to control seedlings. The other treatments did not differ statistically from control or MeJA in terms of subsequent pine weevil damage. For the late exposure group, plants in all induction treatments tended to receive less pine weevil feeding (yet this was not statistically significant) compared to control seedlings. On the other hand, MeJA significantly slowed down seedling growth relative to control and all other induction treatments. Overall, the mechanical damage treatments appeared to have no or variable effects on seedling resistance. One of the treatments, needle-piercing damage, actually increased pine weevil feeding at early exposure. These results therefore suggest that mechanical damage shows little potential as a plant protection measure to reduce feeding by a bark-chewing insect.
|
|
| 2. |
- Chen, Yayuan
(författare)
-
Exploiting plant defenses to protect conifer seedlings against pine weevils
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sweden is one of the top five countries having large planted forest areas, and here the forests are maintained by clear-cut regime, which also promotes the pine weevil (Hylobius abietis), a major threat to Swedish planted coniferous regeneration. Given interest in developing sustainable forest management practices, efficient non-insecticide alternatives are highly demanded to tackle the pine weevil problem. In this thesis, I investigated several potential measures, based on plant defenses, aimed at reducing pine weevil damage to conifer seedlings. Methyl jasmonate (MeJA) is a plant hormone that can trigger plant induced defense/resistance, and reduce pest insect damage in conifers. I examined the compatibility of MeJA treatment with current plant nursery practices, and explored if inflicting mechanical damage can also trigger induced resistance. I also investigated if the timing of MeJA treatment will affect bark wound healing as a plant tolerance trait. I further examined genetic variation in resistance to weevil damage among different families from the Swedish breeding program, and resistance differences between two types of planting materials, seedlings and cuttings. The results confirmed that seedlings exhibit greater resistance to weevil damage when treated with MeJA, even if treatment is applied the previous growing season. In contrast, the evaluated mechanical damage did not trigger strong induced resistance in seedlings. Moreover, if MeJA treatment occurs after seedlings are wounded, healing of bark wounds can be negatively affected, but not if the treatment occurs before wounding. In addition, I found that seedling’s resistance to pine weevil damage is significantly different among families, but the heritabilities of resistance traits were low and may constrain breeding for more resistant seedlings. When examining plant types, cuttings showed higher resistance to pine weevil damage than seedlings from the same family. Further studies should examine the interaction of MeJA-induced seedlings with abiotic and biotic factors under field conditions. The combination of induced resistance with constitutive resistance will also be necessary to fully exploit plant defenses in plant protection.
|
|
| 3. |
- Chen, Yayuan, et al.
(författare)
-
Seasonal timing and recurrence of methyl jasmonate treatment influence pine weevil damage to Norway spruce seedlings
- 2021
-
Ingår i: New Forests. - : Springer Science and Business Media LLC. - 0169-4286 .- 1573-5095. ; 52, s. 431-448
-
Tidskriftsartikel (refereegranskat)abstract
- Defense can be induced in conifer seedlings to reduce pine weevil (Hylobius abietis) damage, by treatment with the plant hormone methyl jasmonate (MJ). Few studies have addressed important practical issues regarding the use of MJ such as treatment incidence and timing, seedling age and its compatibility with plant nursery practices. We examined if levels of pine weevil damage depend on seasonal timing and recurrence of MJ treatment, and if the observed effects depend on plant age. Norway spruce (Picea abies) seedlings from two age cohorts (1 year and 1.5 years old) received four MJ treatments: MJ application before winter storage in the previous year, after winter storage but before spring/summer planting, repeated MJ application (both before winter storage, and before planting) or no MJ application at all. Pine weevil damage was evaluated in a lab and field experiment. We found that the timing and recurrence of MJ treatment affected the amount of damage inflicted by pine weevils in different ways, but these effects were consistent among age cohorts. MJ application before winter storage provided the most effective protection, and this reduction in damage was comparable to that provided by a currently used physical protection method against pine weevil feeding. Our results indicated that MJ can be applied in line with nursery practices (before winter storage) and provides adequate protection for two growing seasons.
|
|
