ARS | Publication request: BACTERIAL POPULATIONS AND THEIR RELATIONSHIP TO WEED SEEDS: IMPLICATIONS FOR SOIL SEED BANK MICROBIAL ECOLOCY.

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract
Publication Acceptance Date: February 27, 2004
Publication Date: May 23, 2004
Citation: Chee-Sanford, J.C., Connor, L.M., Holman, T.J., Tang, E., So, Y., Marvelli, R., Williams, M.M. 2004. Bacterial populations and their relationship to weed seeds: implications for soil seed bank microbial ecology. [abstract].104th Annual Meeting of the American Society for Microbiology, New Orleans,LA. No. N-013.

Technical Abstract: Buried seed reserves, commonly referred to as the soil seed bank, are widely distributed and can persist in the environment. Weed seeds, in particular, are resilient and highly adaptive, and their abundance in soil offers potential for many interactions with native soil microorganisms. As a specialized niche, seeds may provide microorganisms with surfaces for attachment, nutrition, protection, and even means of dispersal. In this study, we used microscopy, terminal restriction fragment (TRF) analysis and ribosomal gene sequences to characterize microbial populations associated, either soil- or seed-borne, with a variety of common weed seeds. The species include velvetleaf, giant ragweed, Pennsylvania smartweed, jimsonweed, and wooley cupgrass. Few fungi and bacteria were loosely associated with some seeds collected directly from plants, but abundant growth and diversity of both fungi and bacteria were found on seeds incubated directly with a variety of soil inocula. PCR-amplified and cloned ribosomal DNA sequences included common soil isolates associated with four major bacterial phyla and a dominance of representatives in the main fungal phylum Ascomycota. Matches between 93-99% sequence identities to bacterial 16S rDNA include members of the genera Flexibacter, Flavobacterium, and Sphingobacterium, and to fungal 18S rDNA primarily associated with the genera Chaetomium, Cephaliophora, and Cordyceps. Analysis of cloned sequences and TRF profiles showed that development of seed-associated populations differed according to individual soils, but within a given soil, a number of common fragments and closely related microbial species were present on replicate seeds, suggesting that there may be some specific relationships. Most seeds, with the exception of velvetleaf, were not decayed over a three-month incubation period in the presence of soil microbial populations. This study investigates the fundamental relationships that may be common between microorganisms and seeds, with broader implications for soil seed bank ecology in many natural systems.