International Journal of Modern Botany
p-ISSN: 2166-5206 e-ISSN: 2166-5214
2013; 3(2A): 26-33
doi:10.5923/s.ijmb.201310.04
Cris G. Hochwender 1, Mary Ellen Czesak 2, Crystal Harmon 1, Brent Mock 1
1Department of Biology, University of Evansville, 1800 Lincoln Ave, Evansville, IN 47722, USA
2Department of Biology, Vassar College, 124 Raymond Ave, Poughkeepsie, NY 12604, USA
Correspondence to: Cris G. Hochwender , Department of Biology, University of Evansville, 1800 Lincoln Ave, Evansville, IN 47722, USA.
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The release of apical dominance following the browsing of stems can alter plant architecture and provide tolerance to herbivore damage. Meristem changes are not associated with foliar damage, so tolerance responses to foliar feeding may not be robustly expressed. In this study, tolerance to foliar damage was characterized for six genetic classes of willows in an interspecific hybrid system (pure Salix eriocephala plants, pure S. sericea plants, F1 hybrids, F2 hybrids, backcrosses to S. sericea, and backcrosses to S. eriocephala). This characterization allowed the genetic architecture of tolerance to be explored. Plagiodera versicolora, a small leaf beetle, was used to inflict foliar damage. Cuttings of genetically identical plants were matched to create a metric of biomass tolerance (defined here as the ratio of biomass for a damaged plant relative to an undamaged plant). Initial size differences between cuttings influenced the relative performance of damaged/undamaged pairs, so a ratio of the cuttings (damaged/undamaged) was calculated using initial wet weights. The ratio of cutting weight explained meaningful variance in biomass tolerance (F1,68 = 71.4; P = 0.0001; r2 = 0.51). Residual variance in biomass tolerance (the variance remaining in biomass tolerance following removal of variance explained by the ratio of cutting weight) was used to reduce the effect of differences in initial plant size for damaged versus undamaged plants. Residual variance in biomass tolerance differed significantly among genetic classes (F5,64 = 2.7; P = 0.03). Using a Tukey post-hoc test, F1 hybrids had significantly greater tolerance to foliar damage than backcrosses to S. sericea. Using line cross analysis, the model expressing the genetic architecture for tolerance in this hybrid system included additive genetic effects (a) + dominance–dominance epistasis (dd). For this willow system, tolerance to damage appears to be a fundamental response, whether damage is associated with browsing or foliar damage. Given the epistatic interactions observed in the current study, coupled together with the potential complexity of growth/storage traits associated with the mechanisms of tolerance, the trajectory for the evolution of tolerance challenges easy interpretations.
Keywords: Compensation, Compensatory Response, Gene Interaction, Herbivory, Heterosis, Hybridization, Speciation
Cite this paper: Cris G. Hochwender , Mary Ellen Czesak , Crystal Harmon , Brent Mock , Genetic Architecture of Tolerance to Foliar Damage in a Salix Hybrid System, International Journal of Modern Botany, Vol. 3 No. 2A, 2013, pp. 26-33. doi: 10.5923/s.ijmb.201310.04.
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![]() | Figure 1. Bar graph representing mean residual variance in biomass tolerance (±SE) for six genetic classes of willow plants. Salix eriocephala plants and their backcrosses are designated as PE and BCE; F1 hybrids and F2 hybrid plants are designated as F1 and F2; S. sericea plants and their backcrosses are designated as PS and BCS. Different lower case letters designate significant differences among genetic classes |
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