DNA-BASED MARKER SYSTEMS TO DETERMINE GENETIC DIVERSITY OF WEEDY SPECIES AND THEIR APPLICATION TO BIOCONTROL

DNA-based molecular markers may provide information about introduced w eedy species that would be useful in biological weed control efforts. Chloroplast DNA restriction fragment length polymorphisms (cpDNA RFLP) and random amplified polymorphic DNA (RAPD) analysis are two DNA-base d marker techniques that can provide estimates of genetic variation in native and introduced populations of weedy species. Profiles provided by these techniques could furnish the necessary information to determ ine the geographic origins of introduced species and provide evidence for multiple introductions. Although DNA-based markers would not neces sarily identify the genetic basis for host-pest compatibility, they wo uld enable identification of specific host genotypes. Current criteria for selecting a weedy species as a target for biological control are primarily political and economic. The importance of genetic diversity and population structure in determining the vulnerability of plant pop ulations to insects or diseases has not been fully appreciated. Estima tes of genetic diversity based on DNA marker analysis could be used as one criteria for determining which plants are targeted for biological control. The success of biological weed control efforts has been limi ted by the high levels of genetic diversity occurring in target weed s pecies and the lack of biocontrol agent and target weed compatibilitie s. DNA-based markers may be used to increase our understanding of thes e factors and contribute to the success of biological weed control by helping to target the most vulnerable species and provide more realist ic expectations of the potential for success given available resources .