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Applied T-RFLP Analyses for the Identification and Characterization of Microbial Populations Associated With Damping-Off Incidence in a Transitional Organic Cropping System

Benitez, Maria Soledad
http://rave.ohiolink.edu/etdc/view?acc_num=osu1218471106

Abstract Details

2008, Doctor of Philosophy, Ohio State University, Plant Pathology.
Within agricultural ecosystems the abundance and activities of diverse microbial populations affecting plant health can be significantly influenced by farm management practices. This work describes the effects of transitional cropping strategies on damping-off incidence and on soil and rhizosphere bacterial, fungal and oomycete communities. Specifically, individual microbial populations were associated with damping-off incidence and the suppression thereof, and two novel bacterial species were characterized for their ability to reduce seedling disease severity. Soils from an organic transition experiment exhibited different levels of damping-off suppression, with a perennial mixed hay transition consistently suppressing damping-off of tomato and soybean. Microbial community analyses were performed from the rhizosphere and surrounding soil of tomato and soybean seedlings grown in soils previously exposed to different transition strategies. The abundance of Pseudomonas and DAPG-producing Pseudomonas populations, did not clearly associate with disease levels. However, the analysis of bacterial, fungal and oomycete community profiles (generated from terminal restriction fragment length polymorphism of 16S and ITS genes, respectively) revealed individual members of the community (expressed as a terminal restriction fragment, TRF) that statistically associated with disease suppression or disease. Bacterial TRF more abundant in the mixed hay suppressive treatment were negatively correlated with disease incidence. In silico analysis of bacterial database sequences indicated that species of known biocontrol agents produce a TRF size corresponding to those identified in this study. Fungal and oomycete TRF abundance and diversity tended to be lower in the mixed hay transition strategy. Fungal and oomycete isolates of the genus Fusarium, Chaetomium and Pythium, among others, generate TRF that match those associated with disease in the studied transition strategies. Sequence information obtained from the bacterial T-RFLP data was used to identify and isolate two novel bacterial species from the mixed hay soils. Mitsuaria and Burkholderia isolates were phylogenetically related to the TRF sequences associated with disease suppression, inhibited pathogen growth in vitro, and reduced seedling disease severity. This work establishes the power of T-RFLP based screening of microbial communities to identify and direct the recovery of functionally important microorganisms in soil.
Brian McSpadden Gardener, B (Advisor)
Warren Dick (Committee Member)
Terrance Graham (Committee Member)
Enrico Bonello (Committee Member)
210 p.
Agriculture; Biology; Ecology; Microbiology; Plant Pathology; Soil Sciences
biological control; community profile; disease suppression

Recommended Citations

Citations

  • Benitez, M. S. (2008). Applied T-RFLP Analyses for the Identification and Characterization of Microbial Populations Associated With Damping-Off Incidence in a Transitional Organic Cropping System [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218471106

    APA Style (7th edition)

  • Benitez, Maria. Applied T-RFLP Analyses for the Identification and Characterization of Microbial Populations Associated With Damping-Off Incidence in a Transitional Organic Cropping System. 2008. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1218471106.

    MLA Style (8th edition)

  • Benitez, Maria. "Applied T-RFLP Analyses for the Identification and Characterization of Microbial Populations Associated With Damping-Off Incidence in a Transitional Organic Cropping System." Doctoral dissertation, Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218471106

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.