BIOLOGICALLY AND ECOLOGICALLY BASED KNOWLEDGE FOR INTEGRATED WEED MANAGEMENT SYSTEMS
Location: Global Change and Photosynthesis Research Unit
Title: INTERACTIONS BETWEEN SOIL MICROORGANISMS AND WEED SEEDS: NOVEL IMPLICATIONS FOR PLANT-MICROBE RELATIONSHIPS
Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 7, 2005
Publication Date: June 5, 2005
Citation: Chee Sanford, J.C., So, Y., Connor, L.M., Holman, T.J., Sanford, R., Sims, G.K. 2005. Interactions between soil microorganisms and weed seeds: novel implications for plant-microbe relationships [abstract]. American Society for Microbiology. Paper No. N-114.
Annual weed species have characteristics of rapid growth and high fecundity, producing numerous, long-lived seeds that contribute to a persistent and extensive soil seed bank. This environment offers opportunities for seed-microbe interactions, with potential importance to plant and microbial community development. To investigate this, TRF analysis and rDNA clone libraries were used to characterize microbial species and community assemblages associated with seeds of several weed species following exposure to soil microorganisms. Further, compounds extracted from viable seeds of different weed species were investigated for their effects on soil microorganisms. Bacterial assemblages generally differed between weed seeds of different species, however, a predominance of species belonging to the major fungal phylum Ascomycota was present, regardless of soil origin. A relationship between woolly cupgrass seeds and fungi with close homologies (98-99%) to Chaetomium globosum was indicated, while species found primarily on Pennsylvania smartweed seeds were related (99%) to Cordyceps sinensis. In contrast, several fungal genera were found associated with velvetleaf seeds, however, these were dominated by species with close homologies (98-99%) to the ascomycete Cephaliophora tropica. These results suggest that weed seeds may support associations with a wide range of soil bacteria, but specific relationships between certain species of seeds and soil-borne fungi may occur. Chemicals extracted from whole seeds of ten weed species demonstrated a range of activities against fungal isolates. For example, water-soluble exudates from seeds of Kochia scoparia significantly inhibited the growth of Colletotrichum graminicola, a soil-borne plant pathogen, while the same extract did not affect the growth of other fungi. Chemical analyses indicated the natural products were comprised of mixtures. This study demonstrates a unique aspect of plant-microbe relationships that may have implications for multi trophic processes involving microbial activities and plant development.