Effects of Simulated and Insect Herbivory on Total and Protein Percipitable Phenolic Concentrations of Two Legumes

Project Overview

GS14-133
Project Type: Graduate Student
Funds awarded in 2014: $9,040.00
Projected End Date: 12/31/2015
Region: Southern
State: Texas
Graduate Student:
Major Professor:
Dr. James Muir
Texas A&M AgriLife Research

Annual Reports

Commodities

  • Agronomic: general hay and forage crops
  • Additional Plants: native plants

Practices

  • Animal Production: feed/forage, animal protection and health, grazing management
  • Pest Management: biological control, integrated pest management
  • Production Systems: organic agriculture

    Abstract:

    A comparison of protein precipitable polyphenolic (PPP) concentrations after simulated and insect herbivory suggested that Desmodium paniculatum and Lespedeza cuneata distinguish between the types of herbivory. Both species decreased leaf PPP concentrations as herbivory intensity increased. Protein binding ability of PPP also declined with herbivory intensity, especially when the plant was entirely defoliated.

    Introduction

    The purpose of this project was to determine if plant CT concentrations differ among control, simulated and insect herbivory. In a study by Pellissier (2013), physiological responses were recorded when simulated herbivory was applied. Pellissier utilized leaf clipping as well as saliva application from ungulate species and added to studies which distinguished physiological responses to physical damage versus responses from the presence of saliva (2013).

     

    This study focused on condensed tannins, secondary phenolic compounds in plants that are believed to serve as the defensive response to herbivory (Levin, 1971). Condensed tannin deposition changes with ontogeny. Cooper et al. (2014), who focused on panicled tick-clover (Desmodium paniculatum (L.) D.C.; PTC) and sericea lespedeza (Lespedeza cuneata (Dum. Cours.) G. Don; SL), found that CT concentration was lowest during the vegetative stage and increased at flowering; however, at seed set, CT concentrations varied between species. The authors hypothesized that this occurred because PTC depends heavily on animals for seed dispersal, while SL does not.

     

    Melanoplus differentialis (differential grasshopper) is common in Texas and is a generalist feeder, known to devastate entire landscapes in a short time (Reinert et al., 2011). It has been observed feeding on SL and PTC and utilized in CT studies (Young and Cantrall, 1955; Hinks et al., 1993).

     

    Studies have been conducted on the relationship between condensed tannins and herbivory, but have not focused on plant response. We hypothesize that the plants will differentiate between simulated and insect herbivory. This knowledge can be used to manipulate CT concentrations in forage crops grown specifically for their anthelmintic or methane-suppression properties.

    Project objectives:

    Determine how varying levels of herbivory (simulated and by differential grasshopper) and plant ontogeny affect:

    1. Phenolic concentration of leaves
    2. Nutrient concentration (nitrogen, carbon, and dry matter) of leaves
    3. Dry matter, phenolic and N yield of regrowth

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.