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

Abstract

Over 18 million hectares of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) 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 (Pinus banksiana Lamb.) hybrids may be more drought-resistant than pure lodgepole pine. We used single-nucleotide polymorphism markers to determine the level of jack pine introgression present in the region J lodgepole pine seed orchard, in northwest Alberta, and we 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 repeg ated drought cycles, withholding water for either 2 or 3 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.