Title page for ETD etd-06232011-211905

Type of Document Master's Thesis
Author Accamando, Amanda K
URN etd-06232011-211905
Title Costs and Benefits of Induced Responses in Soybean
Degree Master of Science (M.S.)
Department Biological Sciences
Advisory Committee
Advisor Name Title
Cronin, James T Committee Chair
Davis, Jeffrey A Committee Member
Elderd, Bret D Committee Member
Stout, Michael J Committee Member
  • Glycine max
  • jasmonic acid
  • induced resistance
  • Chrysodeix includens
Date of Defense 2011-04-27
Availability unrestricted
Herbivorous insects are known to negatively impact plant fitness, such that plants have

evolved defense strategies to reduce the preference and performance of herbivores on those

plants. However, a plantís investment in defense may be costly when herbivores are absent from

the environment. Defense traits that are induced only upon herbivory can mitigate costs

associated with defense maintenance. Although costs and benefits of induced responses are

generally assumed, empirical evidence for them is equivocal. We examined the fitness costs and

benefits of jasmonic acid-induced responses by soybean (Glycine max L. Merr.) in the absence

and presence of soybean loopers (Chrysodeix includens Walker) (Lepidoptera: Noctuidae), an

economically important pest of soybeans in the southern United States. In a greenhouse

experiment we demonstrated that induction was costly to soybeans, affecting all components of

soybean fitness. Jasmonic acid-induced plants produced 10.1% fewer seeds that were 9.0%

lighter, and had 19.2% lower germination rates than control plants. In contrast, induction

provided only modest benefits to soybeans. In a choice experiment, soybean loopers exhibited a

significantly greater preference for leaves from control plants consuming 62% more tissue than

from jasmonic acid- induced plants. Soybean loopers that did feed on induced soybean plants

matured at the same rate and to the same size as soybean loopers that fed on control plants.

However, at high conspecific density, soybean looper survivorship was reduced by 44% on

induced relative to control plants. Negative effects of induction on soybean looper preference

and survivorship did not translate into fitness benefits for soybeans. Our study is the first

evaluation of costs and benefits of soybean induced responses.

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