Plant species and soil type influence rhizosphere bacterial composition and seedling establishment on serpentine soils

Abstract

10Root-associated microbial communities influence plant phenotype, growth and local abundance, 11 yet the factors that structure these microbial communities are still poorly understood. California 12 landscapes contain serpentine soils, which are nutrient-poor and high in heavy metals, and 13 distinct from neighboring soils. Here, we surveyed the rhizoplane of serpentine-indifferent plants 14 species growing on serpentine and non-serpentine soils to determine the relative influence of 15 plant identity and soil chemistry on rhizoplane microbial community structure using 16S rRNA 16 metabarcoding. Additionally, we experimentally examined if locally adapted microorganisms 17 enhance plant growth in serpentine soil. Plant species, soil chemistry, and the interaction 18 between them were important in structuring rhizoplane bacterial communities in both the field 19 and experimental soils. In the experiment, rhizoplane microbial community source influenced 20 seedling survival, but plant growth phenotypes measured were largely invariant to microbial 21 community with a few exceptions. Results from the field sampling suggest that plant species 22 associate with specific microbial communities even across chemically distinct soils, and that 23 microbial communities can differentially influence seedling survival on harsh serpentine soils. 24 Words: 169 25Importance 26Microbial communities on plant roots can influence host plant phenotype, survival, and fitness, 27 with community and ecosystem consequences. However, which factors structure microbial 28 community structure is poorly understood, particularly across large gradients in soil properties. 29The survey and experiment described here shows that plant species host distinct microbiomes 30 despite strong turnover in soil chemistry, although soil type also influences bacterial structure. 31These results suggest that host specificity and soil conditions are both strong drivers of 32 rhizoplane bacterial composition in serpentine ecosystems and influence plant seedling 33 establishment. These results imply that plant species can recruit relatively convergent 34 microbiomes from distinct microbial communities found on different soil types and that soil 35 microbial communities influence seedling establishment. 36 37 38 39 Plant collection 131Plantago erecta, T. fucatum, C. sparsiflora and G. tricolor were collected from two geographically 132

Australian native Glycine clandestina seed microbiota hosts a more diverse bacterial community than the domesticated soybean Glycine max

“…Other plant beneficial traits such as biodegradation, bioactivity, quorum sensing and growth promotion have been documented for some Ochrobactrum strains isolated from soil, rhizosphere and plant roots [71,[76][77][78]. This evidence suggests that exposure to a more natural environment (e.g., native soils and climates) could have resulted in the accumulation of more beneficial bacterial communities to potentially support the fitness of native plants, compared to that of modern cultivars of G. max [65,79,80].…”

Contrasting microbial communities on male and female flowers of a dioecious plant, Mallotus japonicus (Euphorbiaceae)

“…Differences among trees might have already existed prior to flowering. It is also possible that shared microenvironments of the flowers on each individual, such as height, sun exposure, and soil characteristics, could play a role in the colonization and filtering of microbes (Igwe & Vannette, 2019; Tobor‐Kapłon et al, 2006). Although the results of our experiments indicated that some microbes colonize flowers assisted by insects (see below), this colonization might not be sufficient to homogenize flower bacteria among neighboring trees.…”

“…Differences among trees might have already existed prior to flowering. It is also possible that shared microenvironments of the flowers on each individual, such as height, sun exposure, and soil characteristics, could play a role in the colonization and filtering of microbes(Igwe & Vannette, 2019;Tobor-Kapłon et al, 2006). Although the results of our experiments indicated that some microbes colonize flowers assisted by insects (see below), this colonization might not be sufficient to homogenize flower bacteria among neighboring trees.4.3 | Colonization by the dominant bacteriaIt has been reported that insect visitors play important roles in vectoring flower microbes in M. japonicus and many other plant species(Russell et al, 2019;Ushio et al, 2015; Wei et al, 2020), while the importance of dispersal by flower visitors may between male and female flowers or among microbes.…”

Decaying animal matter prevents sprouting in Trifolium repens with no effect on adult plant growth

“…Because soil type directly effects plant nutrient acquisition, stress levels, and growth due to unique microbial communities (Igwe and Vannette, 2018; Michaelis and Diekmann, 2018; Puri et al, 2020), innate pH (Läuchli and Grattan, 2017), differential ability to retain water (Ball, n.d.), and different mineral composition (Singh and Schulze, 2015), soil type has the potential to have a profound effect on plant response to decaying animal matter because decay may proceed differently within different soils. In addition, since natural environments are not homogenous, information concerning how the same plant under the same stressor reacts differently due to soil type is useful from both a forensics and plant physiology perspective.…”