Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2010
Publication Date: 5/11/2010
Citation: Funnell-Harris, D.L., Pedersen, J.F., Sattler, S.E. 2010. Soil and Root Populations of Fluorescent Pseudomonas spp. Associated with Seedlings and Field-grown Plants are Affected by Sorghum Genotype. Plant and Soil Journal. Volume 335: 439-455.
Interpretive Summary: Sorghum planting may reduce growth of weeds and decrease the impact of pathogens such as fungi or nematodes. These effects may be due to compounds, exuded from roots, with allelopathic properties. A growth chamber experiment was conducted with seedlings of wheat and of two different sorghum lines, Redlan and RTx433, grown in soils obtained from two sorghum fields in Nebraska. Numbers of potentially beneficial fluorescent Pseudomonas spp. populations were monitored from roots of each plant and from soil. The plant and the different soils affected the numbers of Pseudomonas spp. on roots or in soil. The two sorghum lines also were grown at the same locations from which the soils were obtained. At one location, the plots were irrigated. Numbers of Pseudomonas spp. and fungi were monitored on roots and in field soil for each sorghum line throughout the growing season. There were differences in numbers of both microorganisms associated with each line and field location. There was a trend for Redlan to have greater numbers of fungi belonging to a group that includes sorghum pathogens on both roots and in soil. Fluorescent Pseudomonas isolates were evaluated for traits that may be antagonistic to other microorganisms. Characteristics of Pseudomonas populations throughout the growing season appeared to fluctuate more on Redlan roots or in field soil, as compared with plots grown with RTx433. This work suggests that the sorghum line planted may have an effect on beneficial and pathogenic microorganisms.
Technical Abstract: Sorghum [Sorghum bicolor (L.) Moench] is valued for bioenergy, feed and food. Aims: Potential of sorghum genotypes to support differing populations of root- and soil-associated fluorescent Pseudomonas spp. or Fusarium spp., in two soils, was assessed. Methods: Culturable pseudomonads were enumerated from roots and soil of sorghum (Redlan and RTx433) and wheat (Lewjain) seedlings repeatedly grown in cycled soils in the growth chamber. Pseudomonads and Fusarium spp. were assessed from roots and soil of field-grown sorghum along with biological control traits hydrogen cyanide (HCN) and 2,4-diacetylphlorogluconol (phl) production. Results: After four four-week cycles, soil associated with Redlan seedlings had greater numbers of fluorescent pseudomonads than Lewjain. In dryland field conditions, RTx433 roots had greater numbers of pseudomonads than Redlan before anthesis but similar numbers after. There were no differences in numbers of pseudomonads from dryland soil or roots or soil of irrigated plants. Percentages of HCN-producing root isolates and phl soil isolates declined on irrigated Redlan plants, but percentages of HCN-producers increased in dryland conditions. Redlan roots had greater percentages of Fusarium isolates in the Gibberella fujikuroi complex. Conclusion: Results indicated that sorghum genotype affected root-associated populations of fluorescent Pseudomonas spp. and Fusarium spp. across soil environments.