Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/24/2003
Publication Date: 11/2/2003
Citation: KIM, S., KREMER, R.J. SCANNING AND TRANSMISSION ELECTRON MICROSCOPY OF ROOT COLONIZATIONS OF MORNING GLORY (IPOMOEA SPP.) SEEDLINGS BY RHIZOBACTERIA. AGRONOMY ABSTRACTS. 2003. CD-ROM (UNPAGINATED). AMERICAN SOCIETY OF AGRONOMY. MADISON, WI.
Technical Abstract: Hydroponically-grown ivyleaf morning glory (Ipomoea hederacea) seedlings inoculated with deleterious rhizobacteria (DRB) were studied to observe the colonization of roots by using scanning and transmission electron microscopy. Bradyrhizobium japonicum isolate GD3, previously isolated as a DRB producing high concentration of indole-3-acetic acid (IAA), and Pseudomonas putida isolate GD4 were compared with a plant growth promoting rhizobacterium (PGPR), Bacillus megaterium isolate GP4. Scanning electron microscopy revealed that the colonization of isolate GD4 was uniformly distributed on the surface of roots; however, isolates GP4 and GD3 were deeply localized in surface furrows of roots. Transmission electron microscopy showed considerable alterations of root cells including vesiculation, partial cell wall degradation, and cytoplasm disorganization. The population of isolate GD4 was 6.653 log c.f.u per cm root, which was significantly higher than isolates GP4 (5.225 log c.f.u per cm root) and GD3 (5.258 log c.f.u per cm root). Root elongation of treated seedlings with isolates GD3 and GD4 was significantly inhibited by 80% and 30%, respectively, compared to the control. Isolate GD3 inhibited root growth partially by secreting a high concentration of IAA (64.02ug/ml). The results suggest that selected DRB may be attractive for supplementing conventional weed management of economically important weeds such as morning glory species, which are difficult to control using many of the currently used herbicides.