Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Accelerated development of bioherbicides to control Palmer amaranth (pigweed).

Abstract

Palmer amaranth (Amaranthus palmeri), commonly referred to as Palmer pigweed, is highly invasive throughout Arkansas and significantly impacts soybean, corn, and cotton production statewide. Numerous attributes of pigweed make it a formidable weed pest, including high levels of seed production per individual plant, the longevity of seeds upon entry into soil seed banks, rapid reproductive development, hardiness in diverse environmental conditions, high levels of genetic variability, and the capacity to develop resistance to diverse herbicides. The arsenal of tools currently available to control pigweed is largely insufficient and/or environmentally unsustainable. Thus, novel tools to control Palmer pigweed are needed urgently. Native, host-specific pathogens of Palmer pigweed could potentially be developed into effective bioherbicides, especially if the virulence of pathogens can be increased through non-transgenic methods. Thus, the objectives of this research were to (1) evaluate fungal pathogens of Palmer pigweed to identify highly aggressive isolates (potential bioherbicide strains) (2) increase the aggressiveness of selected isolates through molecular genetic (non-transgenic) approaches, and (3) evaluate modified strains and select candidates to commercialize as bioherbicides of pigweed. To this end, over 200 strains of pathogenic fungi have been collected from Palmer pigweed throughout Arkansas and evaluated for virulence in greenhouse trials. Several promising strains have been identified, including Colletotrichum isolates that aggressively attack Palmer pigweed, but do not infect soybean or other crop plants. Efforts are underway to increase the virulence of this fungus and other potential bioherbicide candidates through molecular genetics, with the ultimate goal of creating a highly virulent, non-transgenic bioherbicide that induces lethality in Palmer pigweed.