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

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 genotypemore » 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.« less
Authors:
 [1] ;  [2] ;  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
  2. Oregon State Univ., Corvallis, OR (United States). Dept. of Forest Ecosystems and Society
Publication Date:
OSTI Identifier:
1174151
Grant/Contract Number:
FG02-06ER64185; FG02-05ER64113
Type:
Accepted Manuscript
Journal Name:
Arthropod-Plant Interactions
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 1872-8855
Publisher:
Springer
Research Org:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES Genetically modified plants; Gibberellic acid; Non-target plant defense; Plant–insect interactions; Cottonwood leaf beetle; Gypsy moth; populus-tremuloides michx; intraspecific variation; herbivore interactions; phytochemistry; phenolic glycosides; foliar quality