Delivering Sitka spruce with resistance against white pine weevil in British Columbia, Canada

Abstract

The Sitka spruce (Picea sitchensis [Bong.] Carr) breeding program for resistance against the white pine weevil Pissodes strobi Peck (Coleoptera: Curculionidae) is arguably one of the most successful pest resistance breeding programs for plantation forest species in North America, with a substantial proportion of the planting stock in BC and Washington State currently coming from this breeding program. Using conventional selection and breeding, and by screening Sitka spruce populations using artificial weevil infestations, we identified sources of heritable and stable weevil resistance. We also used this program to investigate potential causes behind this resistance and identified several heritable resistance mechanisms, including anatomical characteristics, such as constitutive resin canals and sclereid cells in the bark, terpene defenses and variation in tree phenology. We concluded that resistance is conferred by a suite of traits whose composition varies among resistant sources. In addition, we evaluated the efficiency of screening for resistance using weevil population enhancement as a screening method. Our results culminated in the establishment of seed orchards, and the availability of resistant seed that is contributing to the return of Sitka spruce as a species of choice in coastal British Columbia. Keywords: Picea sitchensis, Pissodes strobi, forest pest management, genetic resistanceDedication: This paper is dedicated to Dr. John Borden of Simon Fraser University (retired) who championed this topic and whose vision inspired so many entomologists in North America -René Alfaro. RÉSUMÉLe programme de sélection de l' épinette de Sitka (Picea sitchensis [Bong.] Carr) visant à accroître la résistance au charançon du pin blanc Pissodes strobi Peck (Coleoptera: Curculionidae) est sans aucun doute l'un des programmes de sélection pour la résistance aux ravageur qui a connu le plus de succès chez les espèces forestières utilisées en plantation en Amé-rique du Nord et il produit une partie importante des stocks plantés actuellement en C.-B. et dans l'État de Washington. En utilisant des méthodes de sélection et de culture classiques, et en soumettant les populations d' épinette de Sitka à des infestations artificielles de charançon, nous avons identifié des sources de résistance au charançon qui sont transmissibles et stables. Nous avons également utilisé ce programme pour étudier les causes potentielles de cette résistance et avons identifié quelques mécanismes de résistance transmissibles, notamment des caractéristiques anatomiques, comme les canaux résinifères transversaux et les cellules sclérites de l' écorce, les terpènes de défense et les variations dans la phéno-logie de l'arbre. Nous en concluons que la résistance vient d'un ensemble de traits dont la composition varie entre les sources résistantes. De plus, nous avons évalué l' efficacité du dépistage pour la résistance en intensifiant des populations de charançon pour effectuer criblage. Nos résultats ont mené à la création de vergers à graines...

Genetic variation in resistance of Norway spruce seedlings to damage by the pine weevil Hylobius abietis

“…Using conventional selection and breeding, for example, has allowed the deployment of Sitka spruce (Picea sitchensis [Bong.] Carr) genetic materials resistant to the white pine weevil Pissodes strobi (Peck), contributing to the return of this species as a choice for planting in British Columbia (Alfaro et al 2013).…”

“…Moreover, variation in resistance could be restricted to single spots or populations. For instance, genetic variation in Sitka spruce resistance against the white pine weevil in British Columbia has been found in just one single provenance, with the remaining populations being uniformly highly susceptible (Alfaro et al 2013). Therefore, the relatively low (52) number of tested families may have been too low to capture the full range of genetic variation.…”

High genetic variation and moderate to high values for genetic parameters of Picea abies resistance to Pissodes strobi

“…In the present study, positive genetic correlations between TH 5 and CWA 6-10 found in the Laroche and Linière trials can be explained by the very high white pine weevil attack rates (83 %; Table 4). Weevils at very high population densities may attack moderately resistant genotypes (Alfaro et al 2013). Significant negative genetic correlations between CWA 6-10 and TH 10 were observed in four of the five trials (b r A from −0.77 to −0.24, Table 4).…”

“…Sitka spruce trees showing stable resistance were identified in clone and family trials. Since 2004, two seed orchards have been producing Sitka spruce resistant to the white pine weevil (Alfaro et al 2013). The…”

“…In Western Canada, genetic variations in resistance to weevil attacks have been well documented for spruce species (Kiss and Yanchuk 1991;King et al 1997King et al , 2004Alfaro et al 2004;Moreira et al 2012;Alfaro et al 2013). Sitka spruce trees showing stable resistance were identified in clone and family trials.…”