Best of both worlds: hybrids of two commercially important pines (Pinus contorta × P. banksiana) combine increased growth potential and high drought tolerance

Over 18 million hectares of lodgepole pine forests have been affected by a massive mountain pine beetle outbreak in western Canada. The ensuing need for reforestation compels forest managers to deploy more drought-resistant stock in anticipation of a hotter and drier future climate. Recent studies suggest that naturally occurring lodgepole pine × jack pine hybrids may be more drought-resistant than pure lodgepole pine. We used single nucleotide polymorphism (SNP) markers to determine the level of jack pine introgression present in the region J lodgepole pine seed orchard, in northwest Alberta, and identified six hybrid genotypes with 10-18% jack pine introgression for further study. We compared the performance of open-pollinated seedlings of lodgepole, jack and hybrid pines under well-watered and drought conditions in a greenhouse experiment. Seedlings were subjected to repeated drought cycles, withholding water for either two or three weeks. We found that hybrid pines grew significantly faster than lodgepole pine under well-watered conditions while retaining the high tolerance to prolonged drought exhibited by lodgepole pine seedlings, a particularly beneficial combination of traits during the critical stage of establishment. We therefore suggest the deployment of hybrid lodgepole pine as a strategy to promote adaptation to hotter and drier future climates.

Determining the instar of mountain pine beetle (Coleoptera: Curculionidae) larvae by the width of their head capsules

Cut-points to distinguish larval instars of the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), from the measurement of head-capsule width were determined using a maximum likelihood approach. The cut-points that distinguish the four instars are suitable to classify individual larvae from field populations collected from lodgepole pine Pinus contorta var. latifolia Engelmann (Pinaceae) or jack pine (P. banksiana Lambert)×lodgepole pine hybrids throughout most of the beetle’s current range in British Columbia and Alberta, Canada. The ability to designate the instar of field-collected larvae will facilitate the calibration of phenology and populations models that assess the climatic suitability of habitats and the potential for MPB to continue expanding its range.

The Needle Volatile Composition of Pinus nigra J. F. Arnold, P. sylvestris L., P. densiflora Siebold et Zucc. and P. thunbergiana Franco Trispecies Hybrids

The needle volatile composition of two trispecies hard pine hybrids produced by the controlled hybridization and their parents was researched with gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) in order to confirm their hybridity. The analysed trispecies hybrids were: (Pinus nigra x P. sylvestris) x P. densiflora (= nisyde) and (P. nigra x P. sylvestris) x P. thunbergiana (= nisyth). A total of 59 compounds was identified. All identified compounds were terpenes, except one. The trispecies hybrids showed the same qualitative pattern of the needle volatile composition as their parental species. However, there were quantitative differences in several major terpenes. According to the needle volatile composition the hybrids nisyde were more similar to the female parent, whereas the hybrids nisyth were more similar to the male parent. The hybrids nisyth had a considerably higher content of β-pinene (specific component of P. thunbergiana) than the other analyzed groups. The content of thunbergol (specific component of P. densiflora) in the hybrids nisyde was not considerably different in relation to the other groups. The intermediary quality of the hybrids nisyde and nisyth for most components in relation to their parents, as well as the previous morphometric analysis, confirms their hybrid character.