Sterile Spikelets Contribute to Yield in Sorghum and Related Grasses.

Sorghum (Sorghum bicolor) and its relatives in the grass tribe Andropogoneae bear their flowers in pairs of spikelets in which one spikelet (seed-bearing or sessile spikelet [SS]) of the pair produces a seed and the other is sterile or male (staminate). This division of function does not occur in other major cereals such as wheat (Triticum aestivum) or rice (Oryza sativa). Additionally, one bract of the SS spikelet often produces a long extension, the awn, that is in the same position as, but independently derived from, that of wheat and rice. The function of the sterile spikelet is unknown and that of the awn has not been tested in Andropogoneae. We used radioactive and stable isotopes of carbon, RNA sequencing of metabolically important enzymes, and immunolocalization of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) to show that the sterile spikelet assimilates carbon, which is translocated to the largely heterotrophic SS. The awn shows no evidence of photosynthesis. These results apply to distantly related species of Andropogoneae. Removal of sterile spikelets in sorghum significantly decreases seed weight (yield) by ∼9%. Thus, the sterile spikelet, but not the awn, affects yield in the cultivated species and fitness in the wild species.

The cost of not acting: Delaying invasive grass management increases costs and threatens assets in a national park, northern Australia.

Globally, invasive grasses are a major threat to protected areas (PAs) due to their ability to alter community structure and function, reduce biodiversity, and alter fire regimes. However, there is often a mismatch between the threat posed by invasive grasses and the management response. We document a case study of the spread and management of the ecosystem-transforming invasive grass, Andropogon gayanus Kunth. (gamba grass), in Litchfield National Park; an iconic PA in northern Australia that contains significant natural, cultural and social values. We undertook helicopter-based surveys of A. gayanus across 143,931 ha of Litchfield National Park in 2014 and 2021-2022. We used these data to parametrise a spatially-explicit spread model, interfaced with a management simulation model to predict 10-year patterns of spread, and associated management costs, under three scenarios. Our survey showed that between 2014 and 2021-22 A. gayanus spread by 9463 ha, and 47%. The gross A. gayanus infestation covered 29,713 ha of the total survey area, making it the largest national park infestation in Australia. A. gayanus had not been locally eradicated within the Park's small existing 'gamba grass eradication zone', and instead increased by 206 ha over the 7-year timeframe. Our modelled scenarios predict that without active management A. gayanus will continue spreading, covering 42,388 ha of Litchfield within a decade. Alternative scenarios predict that: (i) eradicating A. gayanus in the small existing eradication zone would likely protect 18% of visitor sites, and cost ∼AU$825,000 over 5 years - more than double the original predicted cost in 2014; or (ii) eradicating A. gayanus in a much larger eradication zone would likely protect 86% of visitor sites and several species of conservation significance, and cost ∼AU$6.6 million over 5 years. Totally eradicating A. gayanus from the Park is no longer viable due to substantial spread since 2014. Our study demonstrates the value of systematic landscape-scale surveys and costed management scenarios to enable assessment and prioritisation of weed management. It also demonstrates the increased environmental and financial costs of delaying invasive grass management, and the serious threat A. gayanus poses to PAs across northern Australia.

Pseudomonas cultivated from Andropogon gerardii rhizosphere show functional potential for promoting plant host growth and drought resilience.

BACKGROUND: Climate change will result in more frequent droughts that can impact soil-inhabiting microbiomes (rhizobiomes) in the agriculturally vital North American perennial grasslands. Rhizobiomes have contributed to enhancing drought resilience and stress resistance properties in plant hosts. In the predicted events of more future droughts, how the changing rhizobiome under environmental stress can impact the plant host resilience needs to be deciphered. There is also an urgent need to identify and recover candidate microorganisms along with their functions, involved in enhancing plant resilience, enabling the successful development of synthetic communities. RESULTS: In this study, we used the combination of cultivation and high-resolution genomic sequencing of bacterial communities recovered from the rhizosphere of a tallgrass prairie foundation grass, Andropogon gerardii. We cultivated the plant host-associated microbes under artificial drought-induced conditions and identified the microbe(s) that might play a significant role in the rhizobiome of Andropogon gerardii under drought conditions. Phylogenetic analysis of the non-redundant metagenome-assembled genomes (MAGs) identified a bacterial genome of interest - MAG-Pseudomonas. Further metabolic pathway and pangenome analyses recovered genes and pathways related to stress responses including ACC deaminase; nitrogen transformation including assimilatory nitrate reductase in MAG-Pseudomonas, which might be associated with enhanced drought tolerance and growth for Andropogon gerardii. CONCLUSIONS: Our data indicated that the metagenome-assembled MAG-Pseudomonas has the functional potential to contribute to the plant host's growth during stressful conditions. Our study also suggested the nitrogen transformation potential of MAG-Pseudomonas that could impact Andropogon gerardii growth in a positive way. The cultivation of MAG-Pseudomonas sets the foundation to construct a successful synthetic community for Andropogon gerardii. To conclude, stress resilience mediated through genes ACC deaminase, nitrogen transformation potential through assimilatory nitrate reductase in MAG-Pseudomonas could place this microorganism as an important candidate of the rhizobiome aiding the plant host resilience under environmental stress. This study, therefore, provided insights into the MAG-Pseudomonas and its potential to optimize plant productivity under ever-changing climatic patterns, especially in frequent drought conditions.

Climate variability supersedes grazing to determine the anatomy and physiology of a dominant grassland species.

Grassland ecosystems are historically shaped by climate, fire, and grazing which are essential ecological drivers. These grassland drivers influence morphology and productivity of grasses via physiological processes, resulting in unique water and carbon-use strategies among species and populations. Leaf-level physiological responses in plants are constrained by the underlying anatomy, previously shown to reflect patterns of carbon assimilation and water-use in leaf tissues. However, the magnitude to which anatomy and physiology are impacted by grassland drivers remains unstudied. To address this knowledge gap, we sampled from three locations along a latitudinal gradient in the mesic grassland region of the central Great Plains, USA during the 2018 (drier) and 2019 (wetter) growing seasons. We measured annual biomass and forage quality at the plot level, while collecting physiological and anatomical traits at the leaf-level in cattle grazed and ungrazed locations at each site. Effects of ambient drought conditions superseded local grazing treatments and reduced carbon assimilation and total productivity in A. gerardii. Leaf-level anatomical traits, particularly those associated with water-use, varied within and across locations and between years. Specifically, xylem area increased when water was more available (2019), while xylem resistance to cavitation was observed to increase in the drier growing season (2018). Our results highlight the importance of multi-year studies in natural systems and how trait plasticity can serve as vital tool and offer insight to understanding future grassland responses from climate change as climate played a stronger role than grazing in shaping leaf physiology and anatomy.

Evaluation of silage from maize stover, maize husk and Andropogon gayanus in equal level with Tephrosia bracteolata as feed for West African Dwarf sheep.

The study investigated the nutritive composition as well as acceptability of ensiled roughages comprising Andropogon gayanus (AG), maize husk (MH), maize stover (MS) and their mixtures in equal proportion with Tephrosia bracteolata (TB) by West African Dwarf (WAD) sheep. Seven treatment diets were formulated comprising AG: 100% Andropogon gayanus, MH: 100% maize husk, MS: 100% maize stover, TB: 100% Tephrosia bracteolata, AG + TB: 50% Andropogon gayanus + 50% Tephrosia bracteolata, MS + TB: 50% maize husk + 50% Tephrosia bracteolata, MS + TB: 50% maize stover + 50% Tephrosia bracteolata. The experiment was completely randomized in design. Significant variations were observed in the chemical composition of the plant materials before and after ensiling. It was revealed that Tephrosia bracteolata, prior to ensiling, had the highest crude protein (CP) content, lowest crude fibre (CF), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). Similar trend was observed in the chemical composition of Tephrosia bracteolata after ensiling. Inclusion of Tephrosia bracteolata in the roughages improved their nutritional quality. All the silage treatments presented good physical characteristics. The acceptability of the silage by 12 WAD sheep ranked thus: TB > MS + TB > AG + TB > AG > MS > MH + TB > MH. Silage digestibility was highest (66.60%) in TB, closely followed by MH + TB (62.67%) and least in MS. It was concluded that WAD sheep production could be enhanced by feeding ensiled maize plant residues alone or in combination with Tephrosia bracteolata during the lean season.

Dead Rhizophagus irregularis biomass mysteriously stimulates plant growth.

Arbuscular mycorrhizal (AM) fungi establish symbiotic associations with many plant species, transferring significant amounts of soil nutrients such as phosphorus to plants and receiving photosynthetically fixed carbon in return. Functioning of AM symbiosis is thus based on interaction between two living partners. The importance of dead AM fungal biomass (necromass) in ecosystem processes remains unclear. Here, we applied either living biomass or necromass (0.0004 potting substrate weight percent) of monoxenically produced AM fungus (Rhizophagus irregularis) into previously sterilized potting substrate planted with Andropogon gerardii. Plant biomass production significantly improved in both treatments as compared to non-amended controls. Living AM fungus, in contrast to the necromass, specifically improved plant acquisition of nutrients normally supplied to the plants by AM fungal networks, such as phosphorus and zinc. There was, however, no difference between the two amendment treatments with respect to plant uptake of other nutrients such as nitrogen and/or magnesium, indicating that the effect on plants of the AM fungal necromass was not primarily nutritional. Plant growth stimulation by the necromass could thus be either due to AM fungal metabolites directly affecting the plants, indirectly due to changes in soil/root microbiomes or due to physicochemical modifications of the potting substrate. In the necromass, we identified several potentially bioactive molecules. We also provide experimental evidence for significant differences in underground microbiomes depending on the amendment with living or dead AM fungal biomass. This research thus provides the first glimpse into possible mechanisms responsible for observed plant growth stimulation by the AM fungal necromass.

Goat performance on pure Andropogon gayanus pastures or associated with legumes.

The objective of this study was to evaluate the grazing of goats in a grass monoculture system and in intercropping systems of grass + legumes. A randomized block design was adopted, with the treatments arranged in a split-plots scheme. The plots consisted of three cropping systems: monoculture-Andropogon gayanus cv. Planaltina; mixture I-A. gayanus cv. Planaltina + Stylosanthes cv. Campo Grande; and mixture II-A. gayanus cv. Planaltina + Calopogonium mucunoides. The subplots consisted of two grazing cycles. The highest (P = 0.04) total forage mass (TFM) was recorded in the mixture I (A. gayanus cv. Planaltina + Stylosanthes. cv. Campo Grande), which was 2.6 ± 0.1 tons DM/ha. The crude protein (CP) was lower in the monoculture which also showed the highest content of neutral detergent fiber (NDF). The grazing time in the monoculture was the longest (8.23 ± 1.14 h). The goats used a longer time for rumination (P < 0.01) in the mixture I. The lowest (P < 0.01) bite rate was found in mixture II in comparison to the other cropping systems. The bite rate was higher (P < 0.01) in grazing cycle II than in all the other cropping systems. In mixture I, the Stylosanthes cv. Campo Grande, and in mixture II, the C. mucunoides presented the lowest (P < 0.01) δ13C value in the forage. The highest forage intake occurred in the mixture systems (P < 0.01) in comparison to the monoculture. The mixture pastures presented better results for forage mass, nutritive value, and intake in comparison to the monoculture.

Interspecific genetic maps in Miscanthus floridulus and M. sacchariflorus accelerate detection of QTLs associated with plant height and inflorescence.

Miscanthus is recognized as a promising lignocellulosic crop for the production of bioethanol and bioproducts worldwide. To facilitate the identification of agronomical important traits and establish genetics knowledge, two genetic maps were developed from a controlled interspecific cross between M. floridulus and M. sacchariflorus. A total of 650 SSR markers were mapped in M. floridulus, spanning 19 linkage groups and 2053.31 cM with an average interval of 3.25 cM. The map of M. sacchariflorus comprised 495 SSR markers in 19 linkage groups covering 1684.86 cM with an average interval of 3.54 cM. The estimation on genome length indicated that the genome coverage of parental genetic maps were 93.87% and 89.91%, respectively. Eighty-eight bi-parental common markers were allowed to connect the two maps, and six pairs of syntenic linkage groups were recognized. Furthermore, quantitative trait loci (QTL) mapping of three agronomic traits, namely, plant height (PH), heading time (HT), and flowering time (FT), demonstrated that a total of 66 QTLs were identified in four consecutive years using interval mapping and multiple-QTL model. The LOD value of these QTLs ranged from 2.51 to 10.60, and the phenotypic variation explained varied from 9.50 to 37.10%. QTL cluster in syntenic groups MF19/MS7 contained six stable QTLs associated with PH, HT, and FT. In conclusion, we report for the first time the genetic mapping of biomass traits in M. floridulus and M. sacchariflorus. These results will be a valuable genetic resource, facilitating the discovery of essential genes and breeding of Miscanthus.

Local adaptation, genetic divergence, and experimental selection in a foundation grass across the US Great Plains' climate gradient.

Many prior studies have uncovered evidence for local adaptation using reciprocal transplant experiments. However, these studies are rarely conducted for a long enough time to observe succession and competitive dynamics in a community context, limiting inferences for long-lived species. Furthermore, the genetic basis of local adaptation and genetic associations with climate has rarely been identified. Here, we report on a long-term (6-year) experiment conducted under natural conditions focused on Andropogon gerardii, the dominant grass of the North American Great Plains tallgrass ecosystem. We focus on this foundation grass that comprises 80% of tallgrass prairie biomass and is widely used in 20,000 km2 of restoration. Specifically, we asked the following questions: (a) Whether ecotypes are locally adapted to regional climate in realistic ecological communities. (b) Does adaptive genetic variation underpin divergent phenotypes across the climate gradient? (c) Is there evidence of local adaptation if the plants are exposed to competition among ecotypes in mixed ecotype plots? Finally, (d) are local adaptation and genetic divergence related to climate? Reciprocal gardens were planted with 3 regional ecotypes (originating from dry, mesic, wet climate sources) of Andropogon gerardii across a precipitation gradient (500-1,200 mm/year) in the US Great Plains. We demonstrate local adaptation and differentiation of ecotypes in wet and dry environments. Surprisingly, the apparent generalist mesic ecotype performed comparably under all rainfall conditions. Ecotype performance was underpinned by differences in neutral diversity and candidate genes corroborating strong differences among ecotypes. Ecotype differentiation was related to climate, primarily rainfall. Without long-term studies, wrong conclusions would have been reached based on the first two years. Further, restoring prairies with climate-matched ecotypes is critical to future ecology, conservation, and sustainability under climate change.

Selection of suitable reference genes for quantitive real-time PCR normalization in Miscanthus lutarioriparia.

Miscanthus lutarioriparia, which is found widespread in China, has attracted great attention as a most potential bioenergy plant for years. The quantitative real time PCR (RT-qPCR) has appeared as a sensitive and powerful technique to measure gene expression in living organisms during different development stages. In this study, we evaluated ten candidate genes, including 25S ribosomal RNA gene (25S rRNA), actin1 gene (ACT1), carotenoid-binding protein 20 gene (CBP20), glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH), Ubiquitin gene (UBQ), eukaryotic elongation factor 1-αgene (eEF-1α), α-tubulin gene (α-TUB), ß-tubulin gene (ß-TUB), eukaryotic translation initiation factor 4α-1 gene (eIF-4α) and NAC domain protein gene(NAC) in a series of 30 M. lutarioriparia samples followed by statistical algorithms geNorm and Normfinder to analyze the gene expression stability. The results indicated that eIF-4αand UBQ were the most stable expressed genes while CBP20 showed as the least stable among all the samples. Based on above research, we recommend that at least two top-ranked reference genes should be employed for expression data normalization. The best genes selected in this study will provide a starting point to select reference genes in the future in other tissues and under other experimental conditions in this energy crop candidate.

Coexpression network revealing the plasticity and robustness of population transcriptome during the initial stage of domesticating energy crop Miscanthus lutarioriparius.

KEY MESSAGE: Coexpression network revealing genes with Co-variation Expression pattern (CE) and those with Top rank of Expression fold change (TE) played different roles in responding to new environment of Miscanthus lutarioriparius. Variation in gene expression level, the product of genetic and/or environmental perturbation, determines the robustness-to-plasticity spectrum of a phenotype in plants. Understanding how expression variation of plant population response to a new field is crucial to domesticate energy crops. Weighted Gene Coexpression Network Analysis (WGCNA) was used to explore the patterns of expression variation based on 72 Miscanthus lutarioriparius transcriptomes from two contrasting environments, one near the native habitat and the other in one harsh domesticating region. The 932 genes with Co-variation Expression pattern (CE) and other 932 genes with Top rank of Expression fold change (TE) were identified and the former were strongly associated with the water use efficiency (r ≥ 0.55, P ≤ 10-7). Functional enrichment of CE genes were related to three organelles, which well matched the annotation of twelve motifs identified from their conserved noncoding sequence; while TE genes were mostly related to biotic and/or abiotic stress. The expression robustness of CE genes with high genetic diversity kept relatively stable between environments while the harsh environment reduced the expression robustness of TE genes with low genetic diversity. The expression plasticity of CE genes was increased less than that of TE genes. These results suggested that expression variation of CE genes and TE genes could account for the robustness and plasticity of acclimation ability of Miscanthus, respectively. The patterns of expression variation revealed by transcriptomic network would shed new light on breeding and domestication of energy crops.

Amending potential of organic and industrial by-products applied to heavy metal-rich mining soils.

Mining activities promote the development of economies and societies, yet they cause environmental impacts that must be minimized so that their benefits overcome the likely risks. This study evaluated eco-friendly technologies based on the use of low-carbon footprint wastes and industrial by-products as soil amendments for the revegetation of Zn-mining areas. Our goal was to select adequate soil amendments that can be used to recover these areas, with a focus on low-cost materials. The amendments - limestone, sewage sludge, biochar, and composted food remains - were first characterized concerning their chemical composition and structural morphologies. Soil samples (Entisol, Oxisol, Technosol) from three different areas located inside an open-pit mine were later incubated for 60 days with increasing doses of each soil amendment, followed by cultivation with Andropogon gayanus, a native species. The amendments were able to change not only soil pH, but also the phytoavailable levels of Cd, Zn, and Pb. Limestone and biochar were the amendments that caused the highest pH values, reducing the phytoavailability of the metals. All amendments improved seed germination; however, the composted food remains presented low levels of germination, which could make the amendments unfeasible for revegetation efforts. Our findings showed that biochar, which is a by-product of the mining company, is the most suitable amendment to enhance revegetation efforts in the Zn-mining areas, not only because of its efficiency and cost, but also due to its low carbon footprint, which is currently the trend for any "green remediation" proposal.

Arbuscular common mycorrhizal networks mediate intra- and interspecific interactions of two prairie grasses.

Arbuscular mycorrhizal fungi form extensive common mycorrhizal networks (CMNs) that may interconnect neighboring root systems of the same or different plant species, thereby potentially influencing the distribution of limiting mineral nutrients among plants. We examined how CMNs affected intra- and interspecific interactions within and between populations of Andropogon gerardii, a highly mycorrhiza dependent, dominant prairie grass and Elymus canadensis, a moderately dependent, subordinate prairie species. We grew A. gerardii and E. canadensis alone and intermixed in microcosms, with individual root systems isolated, but either interconnected by CMNs or with CMNs severed weekly. CMNs, which provided access to a large soil volume, improved survival of both A. gerardii and E. canadensis, but intensified intraspecific competition for A. gerardii. When mixed with E. canadensis, A. gerardii overyielded aboveground biomass in the presence of intact CMNs but not when CMNs were severed, suggesting that A. gerardii with intact CMNs most benefitted from weaker interspecific than intraspecific interactions across CMNs. CMNs improved manganese uptake by both species, with the largest plants receiving the most manganese. Enhanced growth in consequence of improved mineral nutrition led to large E. canadensis in intact CMNs experiencing water-stress, as indicated by 13C isotope abundance. Our findings suggest that in prairie plant communities, CMNs may influence mineral nutrient distribution, water relations, within-species size hierarchies, and between-species interactions.

Utilization of organic nitrogen by arbuscular mycorrhizal fungi-is there a specific role for protists and ammonia oxidizers?

Arbuscular mycorrhizal (AM) fungi can significantly contribute to plant nitrogen (N) uptake from complex organic sources, most likely in concert with activity of soil saprotrophs and other microbes releasing and transforming the N bound in organic forms. Here, we tested whether AM fungus (Rhizophagus irregularis) extraradical hyphal networks showed any preferences towards certain forms of organic N (chitin of fungal or crustacean origin, DNA, clover biomass, or albumin) administered in spatially discrete patches, and how the presence of AM fungal hyphae affected other microbes. By direct 15N labeling, we also quantified the flux of N to the plants (Andropogon gerardii) through the AM fungal hyphae from fungal chitin and from clover biomass. The AM fungal hyphae colonized patches supplemented with organic N sources significantly more than those receiving only mineral nutrients, organic carbon in form of cellulose, or nothing. Mycorrhizal plants grew 6.4-fold larger and accumulated, on average, 20.3-fold more 15N originating from the labeled organic sources than their nonmycorrhizal counterparts. Whereas the abundance of microbes (bacteria, fungi, or Acanthamoeba sp.) in the different patches was primarily driven by patch quality, we noted a consistent suppression of the microbial abundances by the presence of AM fungal hyphae. This suppression was particularly strong for ammonia oxidizing bacteria. Our results indicate that AM fungi successfully competed with the other microbes for free ammonium ions and suggest an important role for the notoriously understudied soil protists to play in recycling organic N from soil to plants via AM fungal hyphae.

Utilization of organic nitrogen by arbuscular mycorrhizal fungi-is there a specific role for protists and ammonia oxidizers?

Arbuscular mycorrhizal (AM) fungi can significantly contribute to plant nitrogen (N) uptake from complex organic sources, most likely in concert with activity of soil saprotrophs and other microbes releasing and transforming the N bound in organic forms. Here, we tested whether AM fungus (Rhizophagus irregularis) extraradical hyphal networks showed any preferences towards certain forms of organic N (chitin of fungal or crustacean origin, DNA, clover biomass, or albumin) administered in spatially discrete patches, and how the presence of AM fungal hyphae affected other microbes. By direct 15N labeling, we also quantified the flux of N to the plants (Andropogon gerardii) through the AM fungal hyphae from fungal chitin and from clover biomass. The AM fungal hyphae colonized patches supplemented with organic N sources significantly more than those receiving only mineral nutrients, organic carbon in form of cellulose, or nothing. Mycorrhizal plants grew 6.4-fold larger and accumulated, on average, 20.3-fold more 15N originating from the labeled organic sources than their nonmycorrhizal counterparts. Whereas the abundance of microbes (bacteria, fungi, or Acanthamoeba sp.) in the different patches was primarily driven by patch quality, we noted a consistent suppression of the microbial abundances by the presence of AM fungal hyphae. This suppression was particularly strong for ammonia oxidizing bacteria. Our results indicate that AM fungi successfully competed with the other microbes for free ammonium ions and suggest an important role for the notoriously understudied soil protists to play in recycling organic N from soil to plants via AM fungal hyphae.

Appropriate nonmycorrhizal controls in arbuscular mycorrhiza research: a microbiome perspective.

Establishment of nonmycorrhizal controls is a "classic and recurrent theme" in mycorrhizal research. For decades, authors reported mycorrhizal plant growth/nutrition as compared to various nonmycorrhizal controls. In such studies, uncertainties remain about which nonmycorrhizal controls are most appropriate and, in particular, what effects the control inoculations have on substrate and root microbiomes. Here, different types of control and mycorrhizal inoculations were compared with respect to plant growth and nutrition, as well as the structure of root and substrate microbiomes, assessed by next-generation sequencing. We compared uninoculated ("absolute") control to inoculation with blank pot culture lacking arbuscular mycorrhizal fungi, filtrate of that blank inoculum, and filtrate of complex pot-produced mycorrhizal inoculum. Those treatments were compared to a standard mycorrhizal treatment, where the previously sterilized substrate was inoculated with complex pot-produced inoculum containing Rhizophagus irregularis SYM5. Besides this, monoxenically produced inoculum of the same fungus was applied either alone or in combination with blank inoculum. The results indicate that the presence of mycorrhizal fungus always resulted in stimulation of Andropogon gerardii plant biomass as well as in elevated phosphorus content of the plants. The microbial (bacterial and fungal) communities developing in the differently inoculated treatments, however, differed substantially from each other and no control could be obtained comparable with the treatment inoculated with complex mycorrhizal inoculum. Soil microorganisms with significant biological competences that could potentially contribute to the effects of the various inoculants on the plants were detected in roots and in plant cultivation substrate in some of the treatments.

Phenotypic distribution models corroborate species distribution models: A shift in the role and prevalence of a dominant prairie grass in response to climate change.

Phenotypic distribution within species can vary widely across environmental gradients but forecasts of species' responses to environmental change often assume species respond homogenously across their ranges. We compared predictions from species and phenotype distribution models under future climate scenarios for Andropogon gerardii, a widely distributed, dominant grass found throughout the central United States. Phenotype data on aboveground biomass, height, leaf width, and chlorophyll content were obtained from 33 populations spanning a ~1000 km gradient that encompassed the majority of the species' environmental range. Species and phenotype distribution models were trained using current climate conditions and projected to future climate scenarios. We used permutation procedures to infer the most important variable for each model. The species-level response to climate was most sensitive to maximum temperature of the hottest month, but phenotypic variables were most sensitive to mean annual precipitation. The phenotype distribution models predict that A. gerardii could be largely functionally eliminated from where this species currently dominates, with biomass and height declining by up to ~60% and leaf width by ~20%. By the 2070s, the core area of highest suitability for A. gerardii is projected to shift up to ~700 km northeastward. Further, short-statured phenotypes found in the present-day short grass prairies on the western periphery of the species' range will become favored in the current core ~800 km eastward of their current location. Combined, species and phenotype models predict this currently dominant prairie grass will decline in prevalence and stature. Thus, sourcing plant material for grassland restoration and forage should consider changes in the phenotype that will be favored under future climate conditions. Phenotype distribution models account for the role of intraspecific variation in determining responses to anticipated climate change and thereby complement predictions from species distributions models in guiding climate adaptation strategies.

Plant Community Richness Mediates Inhibitory Interactions and Resource Competition between Streptomyces and Fusarium Populations in the Rhizosphere.

Plant community characteristics impact rhizosphere Streptomyces nutrient competition and antagonistic capacities. However, the effects of Streptomyces on, and their responses to, coexisting microorganisms as a function of plant host or plant species richness have received little attention. In this work, we characterized antagonistic activities and nutrient use among Streptomyces and Fusarium from the rhizosphere of Andropogon gerardii (Ag) and Lespedeza capitata (Lc) plants growing in communities of 1 (monoculture) or 16 (polyculture) plant species. Streptomyces from monoculture were more antagonistic against Fusarium than those from polyculture. In contrast, Fusarium isolates from polyculture had greater inhibitory capacities against Streptomyces than isolates from monoculture. Although Fusarium isolates had on average greater niche widths, the collection of Streptomyces isolates in total used a greater diversity of nutrients for growth. Plant richness, but not plant host, influenced the potential for resource competition between the two taxa. Fusarium isolates had greater niche overlap with Streptomyces in monoculture than polyculture, suggesting greater potential for Fusarium to competitively challenge Streptomyces in monoculture plant communities. In contrast, Streptomyces had greater niche overlap with Fusarium in polyculture than monoculture, suggesting that Fusarium experiences greater resource competition with Streptomyces in polyculture than monoculture. These patterns of competitive and inhibitory phenotypes among Streptomyces and Fusarium populations are consistent with selection for Fusarium-antagonistic Streptomyces populations in the presence of strong Fusarium resource competition in plant monocultures. Similarly, these results suggest selection for Streptomyces-inhibitory Fusarium populations in the presence of strong Streptomyces resource competition in more diverse plant communities. Thus, landscape-scale variation in plant species richness may be critical to mediating the coevolutionary dynamics and selective trajectories for inhibitory and nutrient use phenotypes among Streptomyces and Fusarium populations in soil, with significant implications for microbial community functional characteristics.

NMR-based Metabolomics to Study the Cold-acclimation Strategy of Two Miscanthus Genotypes.

INTRODUCTION: Abiotic stress is a major cause of yield loss in plant culture. Miscanthus, a perennial C4 grass, is now considered a major source of renewable energy, especially for biofuel production. During the first year of planting in Northern Europe, Miscanthus was exposed to frost temperature, which generated high mortality in young plants and large loss of yield. One strategy to avoid such loss is to apply cold-acclimation, which confers on plants a better resistance to low temperature. OBJECTIVES: The aim of this study is to describe the effect of a cold-acclimation period on the metabolome of two Miscanthus genotypes that vary in their frost sensitivity at the juvenile stage. Miscanthus × giganteus (GIG) is particularly sensitive to frost, whereas Miscanthus sinensis August Feder (AUG) is tolerant. MATERIALS AND METHODS: Polar metabolite extraction was performed on Miscanthus, grown in non-acclimated or cold-acclimated conditions. Extracts were analysed by 1 H-NMR followed by multivariate statistical analysis. Discriminant metabolites were identified. RESULTS: More than 40 metabolites were identified in the two Miscanthus genotypes. GIG and AUG showed a different metabolic background before cold treatment, probably related to their genetic background. After cold-acclimation, GIG and AUG metabolomes remained different. The tolerant genotype showed notably higher levels of accumulation in proline, sucrose and maltose when subjected to cold. CONCLUSION: These two genotypes seem to have a different adaptation strategy in cold conditions. The studied change in the metabolome concerns different types of molecules related to the cold-tolerant behaviour of Miscanthus. Copyright © 2016 John Wiley & Sons, Ltd.

Uptake of C14-atrazine by prairie grasses in a phytoremediation setting.

Agrochemicals significantly contribute to environmental pollution. In the USA, atrazine is a widely used pesticide and commonly found in rivers, water systems, and rural wells. Phytoremediation can be a cost-effective means of removing pesticides from soil. The objective of this project was to investigate the ability of prairie grasses to remove atrazine. 14C-labeled atrazine was added to sterilized sand and water/nutrient cultures, and the analysis was performed after 21 days. Switchgrass and big bluestem were promising species for phytoremediation, taking up about 40% of the applied [14C] in liquid hydroponic cultures, and between 20% and 33% in sand cultures. Yellow Indiangrass showed low resistance to atrazine toxicity and low uptake of [14C] atrazine in liquid hydroponic cultures. Atrazine degradation increased progressively from sand to roots and leaves. Most atrazine taken up by prairie grasses from sand culture was degraded to metabolites, which accounted for 60-80% of [14C] detected in leaves. Deisopropylatrazine (DIA) was the main metabolite detected in sand and roots, whereas in leaves further metabolism took place, forming increased amounts of didealkylatrazine (DDA) and an unidentified metabolite. In conclusion, prairie grasses achieved high atrazine removal and degradation, showing a high potential for phytoremediation.