Novel Avenues for Plant Protection: Plant Propagation by Somatic Embryogenesis Enhances Resistance to Insect Feeding

Abstract

Somatic embryogenesis (SE), a clonal propagation method utilizing somatic cells, occurs under conditions that activate plant stress adaptation mechanisms such as production of protective secondary metabolites. Surprisingly, possible differences in susceptibility to insect pests between SE-generated and conventionally cultivated plants have not been previously explored. Here, we recorded frequencies and levels of bark-feeding damage by pine weevils (Hylobius abietis) in two large field trials, consisting of emblings (SE-propagated plants) and seedlings from 50 half-sib Norway spruce (Picea abies) families. We found that emblings were less frequently attacked by pine weevils, and when attacked, they were damaged to a lesser extent than seedlings. Moreover, we detected significant additive genetic variation in damage levels received by plants, indicating a heritable component to differences in resistance to insect herbivory among half-sib families. We present first-time evidence that emblings can be more resistant than seedlings to herbivorous insect damage, thus, SE appears to confer a previously unknown plant protection advantage. This finding indicates novel avenues to explore mechanisms underlying plant resistance and new approaches to develop non-toxic measures against insect pests.

Root Rot Resistance Locus PaLAR3 Is Delivered by Somatic Embryogenesis (SE) Pipeline in Norway Spruce (Picea abies (L.) Karst.)

“…Thus, it is possible that the higher activity of the PaLAR3B allele may affect the viability of the young emblings, for instance, by influencing metabolic fluxes and resource allocation in the embling during the first growth season. In a recent study performed with Norway spruce emblings, Puentes et al [34] showed that the SE-propagation method is associated with increased protection against Hylobius abietis damage, and suggested that it may be because the propagation method induces genes involved in the tree's biotic defense, e.g., increasing the production of secondary compounds. Further studies with broader SE materials and conditions in the nursery are needed to clarify the effect of the PaLAR3 allele on the viability of emblings after the first growth season.…”

Blue sky’s the limit? Somatic embryogenesis as a means of propagating recalcitrant blue spruce (Picea pungens) cultivar Hoopsii

“…Mass propagation of desirable conifers could soon be performed at an industrial scale via the use of large-scale immersion bioreactors (Gonzalez-Cabrero et al 2018). Interestingly, propagating Norway spruce via emblings increases the tree's resistance to herbivory by the pine weevil (Hylobius abietis L.), a common conifer pest (Puentes et al 2018). By exposing the embryos and young emblings to stress-inducing conditions during in vitro culturing, the emblings are plausibly 'primed' against herbivory.…”

Control and Management of the Pine Weevil Hylobius abietis L.

“…Thus, there is future potential for developing resistance breeding program in Norway spruce. Additionally, a clonal propagation method (somatic embryogenesis, SE) has been recently shown to confer greater resistance against pine weevils in Norway spruce (Puentes et al, 2018). Plants produced via SE or families with greater resistance could be used for re-planting in sites with high pine weevil pressure.…”