Down-regulation of gibberellic acid in poplar has negligible effects on host-plant suitability and insect pest response Public Deposited

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  • Abstract Endogenous levels and signaling of gibberellin plant hormones such as gibberellic acid (GA) have been genetically down-regulated to create semi-dwarf varieties of poplar. The potential benefits of semi-dwarf stature include reduced risk of wind damage, improved stress tolerance, and improved wood quality. Despite these benefits, modification of growth traits may have consequences for non-target traits that confer defense against insect herbivores. According to the growth-differentiation balance hypothesis, reductions in growth may shift allocation of carbon from growth to chemical resistance traits, thereby altering plant defense. To date, host-plant suitability and pest response have not been comprehensively evaluated in GA down-regulated plants. We quantified chemical resistance and nitrogen (an index of protein) in GA down-regulated and wild-type poplar (Populus alba × P. tremula) genotypes. We also evaluated performance of both generalist (Lymantria dispar) and specialist (Chrysomela scripta) insect pests reared on these genotypes. Our evaluation of resistance traits in four GA down-regulated genotypes revealed increased phenolic glycosides in one modified genotype and reduced lignin in two modified genotypes relative to the non-transgenic wild type. Nitrogen levels did not vary significantly among the experimental genotypes. Generalists reared on the four GA down-regulated genotypes exhibited reduced performance on only one modified genotype relative to the wild type. Specialists, however, performed similarly across all genotypes. Results from this study indicate that although some non-target traits varied among GA down-regulated genotypes, the differences in poplar pest susceptibility were modest and highly genotype-specific.
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  • Buhl, C., Strauss, S. H., & Lindroth, R. L. Down-regulation of gibberellic acid in poplar has negligible effects on host-plant suitability and insect pest response. Arthropod-Plant Interactions, 9(1), 85-95. doi:10.1007/s11829-014-9351-y
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  • 9
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  • 1
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  • This work was supported by the University of Wisconsin (Hatch grant no. WIS01336 to R.L. Lindroth) and the United States Department of Energy’s Poplar Genome-Based Research for Carbon Sequestration in Terrestrial Ecosystems Program (grant nos. DE–FG02–06ER64185 and DE–FG02–05ER64113 to S.H. Strauss).
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