Temporal Dynamics in Rhizosphere Bacterial Communities of Three Perennial Grassland Species

Abstract

Abstract:Rhizodeposition is considered a primary reason for the plant identity effect. However, the detection of distinct rhizosphere bacterial communities (RBC) with different plant species has been variable. The aim of this study was to examine the potential explanations for this variability using three perennial grassland species. In a Kansas field experiment, over two growing seasons, we sampled RBC during the active growth and flowering stages of Agrostis gigantea, Andropogon gerardii and Helianthus maximiliani to: (1) determine the extent of the plant identity effect among these species and if the effect was maintained over time; (2) assess if RBC showed seasonal patterns, corresponding to plant phenology; and (3) examine if soil properties were important for structuring these communities. We found that Helianthus RBC were distinct from those of Agrostis and Andropogon only when Helianthus was flowering. Further, Helianthus RBC exhibited seasonal shifts corresponding to plant phenology. In contrast, Agrostis and Andropogon RBC were similar over time and exhibited gradual non-seasonal changes in compositions. Similar results were observed when accounting for soil properties. Overall, the observance of a plant identity effect depended on the plant species and when RBC were sampled. The seasonality of RBC also depended on the plant species examined.

Diazotrophic bacteria isolated from Brachiaria spp.: genetic and physiological diversity

“…The bacteria from this class responded to chemotactic factors of root exudates and were thus abundant in rhizospheric soils (Costa et al, 2014). However, the profile of exudates dif- fered according to genotype, phenological status, plant nutrition, and seasonality (Murphy et al, 2016). The bacterial colonization of the plant (epiphytic and endophytic colonization) persists through continuous rhizosphere colonization.…”

Diazotrophic Bacterial Community of Degraded Pastures

“…The diazotrophic community can be altered, especially by soil characteristics, by exudation patterns of the plants [32], by type of vegetation, among plant genotypes, by phenological stage, and by niche of colonization [6,10,26,33], besides the action of animals on the vegetation, during grazing [34]. However, the association of these bacteria with forage grasses constitutes an important resource to be used in the recovery of areas with soil and grasses in various stages of degradation [7,30].…”

“…As the fertility of the environment decreases, with the degradation of the pastures, for example, the diversity tends to decrease, because the region becomes selective, leaving only a small part of microorganisms more resistant to unfavorable conditions of the environment [6,26].…”

“…As the pasture degraded, the rhizospheric soil niche showed more diazotrophic bacteria, while there was a reduction in the root-endophytic niche, probably due to the deficient nutrition of the degraded pasture, which did not meet the needs of these microorganisms. The rhizosphere is the region of release of root exudates and concentration of organic matter, which make this niche an environment of microbial interaction and selection [25,26].…”

Peer Review #2 of "Seasonal dynamics alter taxonomical and functional microbial profiles in Pampa biome soils under natural grasslands (v0.1)"

“…Temperature can also indirectly 371 affect microbial communities by reducing plant growth, thereby decreasing carbon 372 rhizodeposition (Murphy et al, 2016). Most plant species of subtropical grasslands are 373 perennial but present lower growth rate and higher senescence rate during the winter.…”