Phenotypic evidence suggests a possible major-gene element to weevil resistance in Sitka spruce

Abstract

The weevil resistance breeding program against the white pine weevil, Pissodes strobi Peck (Coleoptera: Curculionidae), particularly for Sitka spruce (Picea sitchensis (Bong.) Carr), is arguably one of the most successful pest resistance breeding programs for plantation forest species, and it has done a lot to rehabilitate this important western conifer. Nearly all planting stock currently comes from this breeding program and so far the resistance seems effective, durable, and stable. We have used this program to also study causes behind this resistance, including: various hindrance mechanisms including induced and constitutive resin cells, sclereid or stone cells, and terpene defenses. All of them appear factors in resistance, but none singly is strongly predictive to resistance - the strongest are sclereid cells. All of these factors are in their nature complex, multifaceted, and appear to offer some partial solution that is likely controlled by complex multigenic systems. We do note, however, that we have very strongly expressed and complete resistance in some individuals. This and some preliminary data investigation indicates that there may also be a major gene element in our observed resistance. Such elements are well described against rusts and other pathogens in forestry, but are also well described for insects and nematodes in crop breeding. Particularly interesting is the Hessian fly in wheat which has a similar life strategy to the weevil. We describe here the elements that suggest this conjecture and how we might go about proving this. Understanding the genetic elements behind this observed resistance has implications for the overall strength and durability to resistance against the white pine weevil.

Parent Publication

• Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forestry: Disease and insect resistance in forest trees

Citation

King, John N.; Alfaro, René I.; Ott, Peter; vanAkker, Lara. 2012. Phenotypic evidence suggests a possible major-gene element to weevil resistance in Sitka spruce. In: Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J., tech. coords. 2012. Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forestry: Disease and insect resistance in forest trees. Gen. Tech. Rep. PSW-GTR-240. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. pp. 54-64.