Microbial Community Structures in the Rhizosphere of Different Corn Cultivars.

Microbial Community Structures in the Rhizosphere of Different Corn Cultivars.

Noortje Notenbaert, Jesus E. Lopez Vargas, and Charles W. Rice

Department of Agronomy, Kansas State University, Manhattan, KS 66506, USA

Microbial diversity is a key factor in maintaining soil health in both natural and agricultural soils. Plant and soil type affects soil microbial diversity. The genetic modification of plants to increase resilience against pathogens and other stresses may also have an effect on microbial diversity. We hypothesized that the root structures among different corn cultivars are different and would hence impact the microorganisms within the rhizosphere. To test this, we established a greenhouse experiment consisting of four corn cultivars (Assiniboine, B73 x Mo17, DroughtGard, and Roundup Ready) and a control (no plants). The corn seeds were planted in 19-L buckets filled with a 1:1 mixture of a silty clay loam soil and sand. Sampling of soil, roots, and shoots occurred 1, 3, and 6 weeks after emergence. DroughtGard and Roundup Ready corn had the greatest shoot growth after 3 and 6 weeks with similar results for the dry biomass. Roots, on the other hand, had the greatest dry biomass after 6 weeks for B73 x Mo17 and Drought Resistant corn. Phospholipid Fatty Acid (PLFA) analysis was used to determine microbial community structures of the soil. At 1 and 3 weeks, there was a significant (p<0.05) effect with time for relative abundance of Gram + bacteria, Gram – bacteria, and actinomycetes as these groups decreased with time, while the relative abundance of fungi increased. There was significant interaction between cultivar and time for arbuscular mycorrhizal fungi (AMF). The relative abundance for AMF decreased with time but had no significant differences between the cultivars during week 1. During week 3, the relative abundance for B73 x Mo17 became significantly greater than that of Assiniboine and Roundup Ready and the relative abundance for DroughtGard was significantly greater than that of Roundup Ready. Microbial community structures between the different cultivar rhizospheres became more accentuated over time.