Current Research Projects

of the Natural Products Utilization Research Unit

USDA, ARS, University of Mississippi, Oxford, Mississippi

 

Most of the research of this lab is now focused on discovery of natural products for pest management. Later research will focus on producing crops that make these compounds for their own protection. All of the projects below are underway.

 

Off-flavor problem in catfish production - Certain blue-green algae are the source of the off-flavor compounds that bioaccumulate in catfish. We are screening natural products as selective blue-green algicides.  Dr. Kevin Schrader is collaborating with Dr. Craig Tucker of the Delta Research and Experiment Station at Stoneville, MS on this project. 

Fusarium solani - Extracts of this fungus were shown to be toxic to weeds such as sicklepod, velvetleaf, and morningglories. Dr. Dayan is currently investigating the mode of action of a phytotoxin Dr. Rimando isolated. This work is in collaboration with Dr. Hamed Abbas (Southern Weed Science Laboratory, USDA ARS, Stoneville, MS). Contact Dr. Agnes Rimando or Dr. Franck Dayan for more information.

1,8 cineole and cinmethylin - 1,8 cineole is a natural product from which the herbicide cinmethylin was derived.  The mode of action of either of these compounds on plants remain unknown.  We are investigating the possible site(s) of action of these compounds using physiological and biochemical approaches.  Contact Dr. Franck Dayan  to learn more.

Guayule - Current chemical treatments are not wholly effective towards protection against attack of wood by fungi, termites, and other organisms. We have undertaken the discovery of the active components of Parthenium argentatum (Guayule bush) which are responsible for this plant resin's highly fungicidal and termite protecting characteristics. The identification of these components will provide us with insights necessary for development of effective and potent fungicides and termitacides derived from natural sources. 

Leucophyllum frutescens - This desert plant from Texas gave selective phytotoxicity against monocots in an in vitro screening of several other plant species. We are isolating and testing the active compounds for herbicidal activity. This lead came from National Center for Natural Products Research personnel. Contact Dr. Agnes Rimando for more information.

Castela taxana - A promising plant which is highly phytotoxic, and from which was also isolated compounds that were shown to have anti-malarial activity. We are isolating and testing the active compounds for herbicidal activity. This lead came from National Center for Natural Products Research personnel. Dr. Franck Dayan and Susan Watson can give more information.

Oryza sativa (rice) - A specific rice variety from Taiwan which is highly allelopathic to barnyardgrass (the biggest weed problem in rice) in field tests. Identification of the allelochemicals in this variety could lead to further research on breeding allelopathic rice varieties. This project is in collaboration with Dr. Bob Dilday (National Rice Germplasm, Evaluation and Enhancement Center, Stuttgart, AR). Contact Dr. Agnes Rimando for more information.

Sorghum - Sorgoleone has been known as the active photosynthetic inhibitor in several species or sorghum. We are currently using computer modeling techniques to design more potent herbicides with similar structure. There are indications of other phytotoxic constituent(s) in sorghum, which we are attempting to discover. Such a discoveries could lead to breeding studies to give crops major advantages over weeds. We are doing research to determine how these compounds are produced in sorghum species and how they can be used to manage weeds. These studies are is in collaboration with Dr. Leslie Weston (Cornell University). Dr. Franck Dayan  are able to give more information.

Discula destructiva - The phytotoxins of this plant pathogen that infects and kills dogwood are being isolated for evaluation for herbicidal activity. 

Fungicide discovery - All of the compounds discovered by our group and many of those made available by University of Mississippi personnel will be examined for activity against crop pathogens. Contact Dr. David Wedge for more information.

Flourensia cernua (tarbush) - This plant is increasing in dominance within the Chihuahuan Desert of the U.S. It is quite unpalatable to livestock and contains poisonous compounds. To understand herbivore interactions with tarbush and in collaboration with the USDA-ARS' Jornada Experimental Range (JER), we have undertaken discover the components responsible for its unpalatability. This will provide information for the development of tools necessary for the management of our threatened rangelands and for the proper utilization of their resources. 

Drymaria - Several species of Drymaria are associated with the death of cattle in the southwestern US. Previous work has associated the toxicity of Drymaria with compounds known as saponins although, to date, this remains unproved. Work carried at the USDA-ARS's JER in connection with plant-animal interactions gave indications of the presence of a possible toxic component in the volatile fraction of Drymaria pachyphylla. In co-operation with JER we have therefore undertaken to study the isolation, identification, and possible bioactivity of this component of Drymaria.

Cyperin - This phytotoxic natural product has been isolated from several plant pathogens. New modes of herbicide action are needed because of increased weed resistance to herbicides. We have observed an unusually rapid rate of chlorophyll degradation in plants exposed to cyperin. We are investigating this potentially new mode of action. Contact Dr. Steve Duke for more information.

Artemisia annua (annual wormwood) - Annual wormwood produces artemisinin, an anti-malarial drug. This compound is also herbicidally active. Little is known of its mode of action as a pharmaceutical or a herbicide. We are determining how it works as a herbicide and are interacting with university scientists to determine how our findings relate to its effects on the malaria parasite. Dr. Camilo Canel is working on the identification of genes involved in the biosynthesis of artemisinin and related compounds, while Dr. Franck Dayan is working with 3-D modeling to further understand this compound. Dr. Dayan has a picture from this work here.

Hypericum (St. John's wort) - Hypericin is a highly photodynamic compound produced by several St. John's wort species. We are interested in understanding how hypericum compartmentalizes this compound and are investigating the potential use of this compound as a 'contact' pesticide. Contact Dr. Stephen Duke for more information.

Peptidomimetic compounds - We have found several of these compounds are highly phytotoxic. We are interested in discovering their mode(s) of action and plan on utilizing computer modeling techniques to maximize their activity. These molecules were synthesized by Dr. Jordan Zjawiony, of the University of Mississippi with whom we are collaborating on this project. Contact Dr. Franck Dayan for more information.

Terpenoid metabolism - Many pesticidal compounds from plants are terpenoids. A visiting scientist from Spain is investigating the enzymes of this pathway and how they might be manipulated. This work involves working with cloned genes and gene products. It will be useful to the scientists involved in the project below. Contact Dr. Steve Duke for more information.

Transgenic crops with natural pest resistance - The objective is to improve production of existing natural compound defenses of crops to pests and to put new natural compound defenses into crops. 

Anti-cancer ellagitannins from small fruits - This project is a multi-institutional collaboration involving cancer prevention using small fruits between Dr. David Wedge; Dr. Lyndon Larcom, (Clemson University, Clemson SC); and Dr. Daniel Nixon (Hollings Cancer Center, Medical University of South Carolina, Charleston SC.) The project will focus on isolation of natural compounds from strawberries, grapes and raspberries that have anticancer and antimicrobial activity. This work is funded by the USDA Fund For Rural America.

 

Current Research Partners

Home | Projects | Personnel | Publications