Location: Chemistry Research2012 Annual Report
1a. Objectives (from AD-416):
1. Determination of physiological and biochemical mechanisms, elicitors, and regulators involved in the interactions of plants with insects and their natural enemies. 1a. Isolation and identification of elicitors or biotic agents of induced plant volatile emission and other inducible plant defenses. 1b. Elucidation of the signaling interactions that mediate insect and insect elicitor induced plant defenses and volatile emission. 2. Identification and evaluation of chemicals that regulate or influence behaviors, including foraging, mating and oviposition, of important pest insects. 2a. Isolate and identify plant volatiles and insect produced pheromones that in combination attract male and female pepper and cranberry weevils. 2b. Identification of oviposition deterring pheromone from pepper weevil. 2c. Interaction between Insect and Host Volatiles on Reproductive Development of Anastrepha spp. (Dipera:Tephrididae). 2d. Identification of oviposition deterring pheromones for Tephritid Fruit Flies. 2e. Influence of Fruit Volatiles on attraction of Small Hive Beetle.
1b. Approach (from AD-416):
Identify and evaluate chemicals that regulate or influence behaviors, including foraging, mating and oviposition, of important pest insects. Determine the physiological and biochemical mechanisms, elicitors, and regulators involved in the interactions of plants with insects, insect natural enemies and other organisms. This research will utilize numerous interactive bioassays with insects, plants, purified biochemicals and other organisms. Isolation and identification of new bioactive chemicals that mediate insect behaviors and plant-insect interactions will be achieved using a combination of approaches including preparative GC, HPLC, preparative flash chromatography, GC/MS, FT-IR, NMR, micro-degradation and synthesis where applicable. Major target insects for this research will include pest Lepidoptera, Coleoptera and Diptera that attack fruit and vegetables and coleopteran pests of Honey Bees. Other target insects may be selected as needed during progression of the project.
3. Progress Report:
Studies were continued to uncover additional acidic terpenoid defenses in maize. Isolation, identification, and biochemical assays against insects and fungi are currently ongoing. Studies on biochemical signals that regulate these terpenoid defenses in maize indicate a role for a new series of oxylipin signals. These oxylipins are predominantly localized to infected tissue and exhibit rapid programmed cell death activity. The newly discovered oxylipin signals are likely to play important roles in many different crops. Studies were conducted to examine the interactive role of herbivore-induced volatiles and male aggregation pheromones for pepper and cranberry weevils. A small scale field trial showed preferential capture of mated pepper weevil females by a host plant based attractant blend and that a single plant produced compound is important for synergizing pheromone attraction for cranberry weevils. GC/MS analyses of volatiles and extracts of oviposition plugs from pepper weevils resulted in identification of two components responsible for oviposition deterrence. A combination of these compounds is being evaluated in small scale field assays. These new discoveries in addition to previously evaluated harmless mineral and organic deterrents will be evaluated for use in a push pull weevil control strategy. Incidence of host-marking behaviour and its efficacy in deterring conspecific and heterospecific oviposition were investigated in six major African mango fruit fly species. Host-marking behaviour of C. capitata, C. cosyra, C. fasciventris and C. rosa elicited at least conspecific or heterospecific oviposition deterrence or attraction and suggested potential of the host-marking technique for the management these species. Flight tunnel bioassays using Small hive beetles established that volatiles from ripe fruit were preferred over the most effective attractant from beehives. Biological and electrophysiological studies resulted in identification of a highly attractive blend of fruit produced volatiles which is more attractive in the field than the currently used monitoring lures.
1. Hormone therapy accelerates reproductive development in Tephritid fruit flies. Documentation that juvenile hormone is pivotal in coordination of sexual signaling with reproductive development in Tephritid fruit flies led to developing methods to improve efficacy of the Sterile Insect Technique (SIT) used to control these pests by incorporating the juvenile hormone analog methoprene along with protein into adult diets for sterile flies. Flies fed on a diet containing methoprene plus a protein supplement became sexually mature 4-7 days earlier than those fed diets that did not contain the supplements. These males were also more attractive than control treated males in attracting wild mates. Thus, treated flies mated at a younger age which reduced mortality and mated more frequently than did untreated flies normally used for SIT. This research resulted in the International Atomic Energy Agency and Food and Agricultural Organization (IAEA/FAO)including the technology in a coordinated research program to develop methods to improve efficacy of SIT. The technology was found to improve reproduction by sterile males of many species and is now used in Mexico to improve reproductive performance of sterile Mexican fruit flies released to control natural populations.
2. European Corn Borer overcomes plant defense and induces protein production in maize. Studies were conducted to gain insight on how European corn borer either overcome or subvert inducible plant defenses in maize. After multiple days of stem attack, both plant defenses and total protein significantly increase. European corn borer growth is greatly improved in previously attacked stems demonstrating insect-induced plant susceptibility. Also high levels indole-3-acetic acid (IAA) exist in European corn borer frass but not other common Lepidopteran pests. The synthetic auxin analog, 2,4-D, promoted increased protein accumulation. Inhibition of auxin production by European corn borer larvae may provide a new target and strategy to reduce pest virulence.
O'Doherty, I., Yim, J.J., Schmelz, E.A., Schroeder, F.C. 2011. Synthesis of the Caeliferins, elicitors of plant immune responses: accessing Lipophilic natural products via cross metathesis. Organic Letters. 13(21):5900-5903.