Bermudagrass Growth Research Articles

Ironstone and red mud barriers to reduce subsurface movement of soil phosphorus.

Loss of phosphorus in seepage may contribute to eutrophication of downstream water bodies. This study examined the potential use of pedogenic ironstone and untreated red mud (bauxite refining residue) as P sorbents in a permeable reactive barrier (PRB) to mitigate such loss. Effects of ironstone and red mud on P sorption (batch), transport (columns), saturated hydraulic conductivity (KS), and growth of common bermudagrass (Cynodon dactylon; greenhouse) were examined. Both materials had sorption maxima of ∼30mmol Pkg-1 or about five times that of a P-enriched sandy soil; however, sorption by red mud greatly increased with decreasing pH. Transport of P through columns of ironstone and red mud (diluted with nonreactive sand) was similar and slower compared to soil+sand. However, when red mud was mixed with soil, increased sorption at lower pH resulted in greater P retention compared to ironstone+soil (76%vs. 13%). Although addition of ironstone to soil up to 20% did not reduce KS, red mud at even 5% did. Soil amendment with red mud increased bermudagrass growth and P uptake. Given long-term neutralization of red mud in an acidic soil and increased P sorption, it may be suitable in a PRB if incorporated at a low rate and/or co-incorporated with a coarser material.

Onion Peel Waste Has the Potential to Be Converted into a Useful Agricultural Product to Improve Vegetable Crop Growth

The onion processing industry produces hundreds of thousands of tons of onion waste annually. Normally, onion peel waste is dumped in landfills, which creates additional sources of greenhouse gases. Research has validated that onion peel is a concentrated source of bioactive compounds; therefore, it can be turned into useful agricultural products such as soil amendments and possibly biostimulants. This study conducted three experiments to investigate the plant growth-promoting potential of an onion juice concentrate (OJC). The first experiment explored whether the application of OJC could increase plant growth of Bermuda grass, lettuce, and bok choy. The second experiment evaluated the effects of foliar and subsurface drench applications of OJC on bok choy and lettuce growth. The third experiment investigated the interaction between OJC application methods and fertilizer type on bok choy and radish growth. The results indicated that foliar applications of OJC of 1% to 2% concentrations increased the yield of bok choy and its overall growth. Subirrigation with OJC, however, enhanced the root growth of bok choy, lettuce, and radish. Notably, the combined approach of foliar and subirrigation applications further promoted the growth of both bok choy and radish. Comparing across experiments, longer OJC application periods emerged as a promising strategy for amplifying its growth-promoting benefits. Overall, our findings suggest that OJC holds promise for promoting sustainable agriculture. This potential comes from its ability to enhance both the growth and yield of vegetable crops like bok choy, lettuce, and radish while simultaneously reducing waste.

Removing grass clippings reduces bermudagrass mite (Acari: Eriophyidae) infestation during turfgrass regrowth.

Bermudagrass mite (Aceria cynodoniensis Sayed) infestation stunts bermudagrass (Cynodon spp. [Poales: Poaceae]) growth, leading to thinned turf and lower aesthetic and recreational value. Bermudagrass mites cause characteristic symptoms called witch's brooms, including shortened internodes and leaves and the proliferation of tillers. Grass clippings produced by mowing or scalping bermudagrass harbor mites, which abandon the desiccating grass clippings and spread to surrounding turfgrass. Dropped grass clippings can lead to infestation of new turfgrass. Nursery experiments were conducted with potted bermudagrass to determine the effect of removing witch's brooms or grass clippings after scalping on witch's broom densities on the recovering bermudagrass. Additionally, laboratory experiments were conducted to assess the potential for mites to abandon detached witch's brooms and to evaluate mite survival after leaving their hosts. The number of initial witch's brooms and individually removing witch's brooms did not affect subsequent witch's broom densities, suggesting that infested but asymptomatic terminals later developed into witch's brooms. Removing grass clippings after scalping reduced witch's broom densities by over 65% in two trials. Most mites (96%) abandoned witch's brooms within 48h after detaching witch's brooms, and adult mites survived an average of 5.6h after removal from the host plant. Removing clippings after scalping may improve bermudagrass mite management and limit damage on the recovering turfgrass. Additionally, clippings resulting from regular mowing or scalping should be disposed of properly because this study demonstrates that mites abandon desiccating host plants and survive sufficiently long to infest surrounding turfgrass.

Assessment of the changes in growth, photosynthetic traits and gene expression in Cynodon dactylon against drought stress

Drought stress considered a key restrictive factor for a warm-season bermudagrass growth during summers in China. Genotypic variation against drought stress exists among bermudagrass (Cynodon sp.), but the selection of highly drought-tolerant germplasm is important for its growth in limited water regions and for future breeding. Our study aimed to investigate the most tolerant bermudagrass germplasm among thirteen, along latitude and longitudinal gradient under a well-watered and drought stress condition. Current study included high drought-resistant germplasm, “Tianshui” and “Linxiang”, and drought-sensitive cultivars; “Zhengzhou” and “Cixian” under drought treatments along longitude and latitudinal gradients, respectively. Under water deficit conditions, the tolerant genotypes showed over-expression of a dehydrin gene cdDHN4, antioxidant genes Cu/ZnSOD and APX which leads to higher antioxidant activities to scavenge the excessive reactive oxygen species and minimizing the membrane damage. It helps in maintenance of cell membrane permeability and osmotic adjustment by producing organic osmolytes. Proline an osmolyte has the ability to keep osmotic water potential and water use efficiency high via stomatal conductance and maintain transpiration rate. It leads to optimum CO2 assimilation rate, high chlorophyll contents for photosynthesis and elongation of leaf mesophyll, palisade and thick spongy cells. Consequently, it results in elongation of leaf length, stolon and internode length; plant height and deep rooting system. The CdDHN4 gene highly expressed in “Tianshui” and “Youxian”, Cu/ZnSOD gene in “Tianshui” and “Linxiang” and APX gene in “Shanxian” and “Linxiang”. The genotypes “Zhongshan” and “Xiaochang” showed no gene expression under water deficit conditions. Our results indicate that turfgrass show morphological modifications firstly when subjected to drought stress; however the gene expression is directly associated and crucial for drought tolerance in bermudagrass. Hence, current research has provided excellent germplasm of drought tolerant bermudagrass for physiological and molecular study and future breeding.

Impact of Biochar on Pathogenic Bacteria and Bermuda Grass (Cynodon dactylon) Growth in Soil Treated with Chicken Manure

Chicken manure plays an important role in soil amendment by improving soil properties for plant growth. However, the high levels of pathogens can have an adverse effect on humans when used for sports turf. This study was conducted to 1) determine the pathogenic bacteria in chicken manure-amended soil, 2) identify the appropriate decomposition stage of manure associated with reduced number of pathogenic bacteria, 3) assess the effect of different rates of biochar on pathogenic bacteria in the amended soil and 4) determine the effect of biochar on the growth of Bermuda grass. The design used for the laboratory experiment was 3˟3 factorial in Completely Randomised Design (CRD) and it was replicated three times. The factors involved were: decomposition stages of chicken manure (3 levels) and the different rates of biochar (3 levels). The best combination of biochar and chicken manure at the percentages of 0, 5, 10, and 15 were then used together with soil and sand mix at a ratio of 100:00 and 70:30 to plant Bermuda grass. This experiment showed that E. coli was present in chicken manure and that increasing the decomposition period had a significant effect on the E. coli by reducing its load. Also, the addition of biochar to the chicken manure resulted in a significant reduction of E. coli count (p<0.01). The soil amended with the biochar and manure also supported very well the growth of Bermuda grass with the 10% and 15% biochar manure mix in 70 to 30 ratio of topsoil and sand giving the best grass growth in terms of spread, thickness, height, and color. A regression analysis given by the equation Y(coverage)=176.857-23.0402(sprouting) (R2=0.99), indicated that sprouting significantly affected grass coverage such that 99% variation in the grass coverage was attributed to the sprouting. At the end of the study, it was concluded that well-composted chicken manure should be used together with biochar on sports fields to help remediate the problem of E. coli infestation and also improve the growth of grass on fields. Furthermore, biochar with chicken manure-amended soil could be ideal for vegetable garden to help reduce foodborne diseases caused by E. coli infestation.

Uso de bioestimulantes no crescimento inicial da grama DiscoveryTM

Abstract The use of bacteria and seaweed extracts as biostimulants to enhance plant growth holds promise for sustainable turfgrass management. This study aimed to investigate the effects of soil application of Azospirillum brasilense (bacterium) and Ascophyllum nodosum (seaweed) extract on the initial growth of DiscoveryTM bermudagrass. The study was conducted using a completely randomized design with plots measuring 0.25 m², each with a 0.5 m border. Two separate experiments were conducted, each involving four doses of biostimulants and five repetitions. The biostimulant treatments consisted of 0, 2, 4, and 6 mL L¹ A. brasilense inoculant and 0, 5, 10, and 15 mL L¹ A. nodosum seaweed extract. These treatments were uniformly applied to the soil at a rate of 100 mL m², with applications at 0, 30, and 60 days after the start of the experiment. After 90 days, the parameters green color index, green cover rate, turfgrass height, and vegetation index (normalized difference), were evaluated. The results indicated that both biostimulants significantly promoted the initial growth of DiscoveryTM bermudagrass. As the doses of the biostimulants increased, there was a corresponding increase in biomass and improved development of the turfgrass. The most pronounced responses were observed with a dose of 6 mL L¹ of the bacteria inoculant and 15 mL L¹ of the seaweed extract. These biostimulants fostered better turf coverage, making it challenging for weeds to establish, and potentially accelerating the production of sod grass.

Differential Regulations of Antioxidant Metabolism and Cold-Responsive Genes in Three Bermudagrass Genotypes under Chilling and Freezing Stress.

As a typical warm-season grass, bermudagrass growth and turf quality begin to decrease when the environmental temperature drops below 20 °C. The current study investigated the differential responses of three bermudagrass genotypes to chilling stress (8/4 °C) for 15 days and then freezing stress (2/-2 °C) for 2 days. The three genotypes exhibited significant variation in chilling and freezing tolerance, and Chuannong-3, common bermudagrass 001, and Tifdwarf were ranked as cold-tolerant, -intermediate, and -sensitive genotypes based on evaluations of chlorophyll content, the photochemical efficiency of photosystem II, oxidative damage, and cell membrane stability, respectively. Chuannong-3 achieved better tolerance through enhancing the antioxidant defense system to stabilize cell membrane and reactive oxygen species homeostasis after being subjected to chilling and freezing stresses. Chuannong-3 also downregulated the ethylene signaling pathway by improving CdCTR1 expression and suppressing the transcript levels of CdEIN3-1 and CdEIN3-2; however, it upregulated the hydrogen sulfide signaling pathway via an increase in CdISCS expression under cold stress. In addition, the molecular basis of cold tolerance could be associated with the mediation of key genes in the heat shock pathway (CdHSFA-2b, CdHSBP-1, CdHSP22, and CdHSP40) and the CdOSMOTIN in Chuannong-3 because the accumulation of stress-defensive proteins, including heat shock proteins and osmotin, plays a positive role in osmoprotection, osmotic adjustment, or the repair of denatured proteins as molecular chaperones under cold stress. The current findings give an insight into the physiological and molecular mechanisms of cold tolerance in the new cultivar Chuannong-3, which provides valuable information for turfgrass breeders and practitioners.

Hybrid Bermudagrass Responses to Impaired Water Sources

Low-quality (i.e., impaired) water sources are commonly used to irrigate warm-season turfgrass landscapes as a result of limited supplies of potable water sources. Currently, there is great need to define the impacts of impaired water sources on turfgrass water consumption, growth, and quality. The objectives of this study were to characterize actual evaporation (ETa), clipping production, and quality of three hybrid bermudagrass varieties [‘TifTuf’, ‘Tifway’, and ‘Midiron’; Cynodon dactylon (L.) Pers. × C. traansvalensis Burtt Davy] grown under three water sources [reverse osmosis (RO), local well, and recycled], each supplied at full irrigation levels (1.0 × ETa) over two 8-week study periods. When pooling across water source and date, TifTuf maintained the highest visual quality and normalized difference vegetation index (NDVI) compared with both Midiron and Tifway. This was accompanied by a greater daily ETa rate, clipping production, and water use efficiency (WUE) compared with Midiron in both studies. When pooling across variety and date, daily ETa of turfgrass receiving recycled water was 5% to 10% less than those receiving the local well or RO water. In addition, turfgrasses receiving local well water held the greatest visual quality and NDVI compared with those receiving either RO water in the summer study. Visual quality and NDVI were also less in turfgrasses receiving RO water compared with those receiving local well or recycled water in the fall. Despite turfgrasses having a lower ETa under recycled water in both study periods, these plants had significantly greater clipping production compared with RO water in the summer. Also, clipping production under recycled water did not differ significantly from the other two sources in the fall study. Furthermoe, in both studies, WUE was similar for turfgrasses receiving recycled water compared with those receiving RO or local well water. Results demonstrated that irrigation water quality influences critical factors for hybrid bermudagrass growth and that considerable variability exists among three commercially available varieties for evapotranspiration rates, quality, and clipping production.

Effects of hydrogen sulfide on grass traits and water-gas transport in grass-planted unsaturated soil

Vegetation has been found to improve the hydrological performance of landfill cover. However, existing studies ignore the effects of hydrogen sulfide (H2S), which forms the toxic odour generated from municipal solid wastes. Hydrogen sulfide is a potential signalling molecule in regulating plant-stomata aperture, but how the plant–hydrogen sulfide interaction affects the water–gas transport in soil remains unknown. This aim of this study was to investigate the effects of hydrogen sulfide on Bermuda grass growth and its influence on water–gas transport in unsaturated soils. Soil columns, with and without vegetation, were prepared and fumigated with different hydrogen sulfide concentrations. These columns were subjected to controlled drought and rainfall sequentially. The results showed that grass leaves almost wilted without hydrogen sulfide fumigation due to the Pythium diseases caused by the antecedent waterlogged conditions. In contrast, hydrogen sulfide fumigation promoted grass growth because of the fungicidal effects of hydrogen sulfide. In drought, hydrogen sulfide fumigation caused stomata closure, which resulted in a lower matric suction in the vegetated soil than that without hydrogen sulfide fumigation. Accordingly, hydrogen sulfide concentration reduced because of oxidation by metal oxides in soil. Upon subsequent rainfall, more infiltration but lower matric suction was observed in vegetated soils than was found in the bare case, whereas hydrogen sulfide concentration decreased continuously due to gas dissolution in the pore water. Direct application of laboratory findings herein to field cases should be used with caution, because the applied continuous lighting and low evapotranspiration rate of the soil column tests may not be representative of field conditions.

Effects of Shade Stress on Growth and Responsive Mechanisms of Bermudagrass (Cynodon dactylon L.)

Effects of Shade Stress on Growth and Responsive Mechanisms of Bermudagrass (Cynodon dactylon L.)

Response of Warm Season Turf Grasses to Combined Cold and Salinity Stress under Foliar Applying Organic and Inorganic Amendments

Turfgrasses are considered an important part of the landscape and ecological system of golf courses, sports fields, parks, and home lawns. Turfgrass species are affected by many abiotic stresses (e.g., drought, salinity, cold, heat, waterlogging, and heavy metals) and biotic stresses (mainly diseases and pests). In the current study, seashore paspalum (Paspalum vaginatum Sw.) and Tifway bermudagrass (Cynodon transvaalensis Burtt Davy × C. Dactylon) were selected because they are popular turfgrasses frequently used for outdoor lawns and sport fields. The effect of the combined stress from both soil salinity and cold on these warm season grasses was investigated. Some selected organic and inorganic amendments (i.e., humic acid, ferrous sulphate, and silicon) were applied as foliar sprays five times during the winter season from late October to March. This was repeated over two years in field trials involving salt-affected soils. The physiological and chemical parameters of the plants, including plant height; fresh and dry weight per plot; total chlorophyll content; and nitrogen, phosphorus, iron, and potassium content, were measured. The results showed that all the studied amendments improved the growth of seashore paspalum and Tifway bermudagrass during this period compared to the control, with a greater improvement observed when using ferrous sulphate and humic acid compared to silicon. For seashore paspalum, the highest chlorophyll content in April was recorded after the application of ferrous sulphate at a level of 1000 ppm. The current research indicates that when grown on salt-affected soils, these amendments can be used in warm-season grasses to maintain turf quality during cold periods of the year. Further research is needed to examine any negative long-term effects of these amendments and to explain their mechanisms.

Growth, Photosynthesis, and Gene Expression of Bermudagrass in Response to Salinity and Shade Stress

Soil salinization is an environmental problem globally. Bermudagrass (Cynodon dactylon) has long been used for soil restoration in saline-alkali land. Urbanization and the compound planting pattern combining trees, bushes, and grasses induced shading are becoming one of the most significant environmental constraints on the management of bermudagrass, which directly affects photosynthetic characteristics. Salinity and shade have become the most important environmental constraints on lawn development and implementation. Previous studies have shown that the plant physiological response under combined stress was different from that under single stress. The purpose of this research was to investigate the effects of salinity stress, shade stress, and the combined stress on bermudagrass. Shade nets were used to simulate shade stress to 85% shade. The NaCl concentration gradient for salinity stress was 1.0% for 7 days, 1.5% for 7 days, and 2.0% for 13 days, respectively. The combined stress combines the two approaches mentioned previously. The results showed that the salinity stress significantly inhibited the plant height, leaf relative water content, chlorophyll content, the chlorophyll a fluorescence induction (OJIP) curve and other photosynthetic parameters of bermudagrass while increasing electrolyte leakage when compared with control. Shade stress significantly enhanced the plant height, chlorophyll content, electrolyte leakage, the OJIP curve, and other photosynthetic parameters. Under the combined stress, the plant height and relative water content did not change significantly, but the photosynthetic parameters such as chlorophyll content and the OJIP curve increased. Furthermore, under the combined stress, the photosynthesis-related genes were regulated. Salinity stress inhibited the photosynthetic ability of bermudagrass more than shade stress, while the combined stress exhibited a considerably better photosynthetic ability. These findings provide information for the usage of bermudagrass in salinized shade conditions.

Potential Allelopathic Effect of Wheat Straw Aqueous Extract on Bermudagrass Noxious Weed

Residues of several crops, including wheat, have a promising allelopathic effect on noxious weed species and thus represent eco-friendly alternatives to harmful, widely applied herbicides. The current investigation deals with the effects of wheat straw aqueous extract on the growth and biochemical aspects of bermudagrass (Cynodon dactylon L.) as a model of harmful weeds for the wheat crop. The prepared aqueous extract from wheat straw was subjected to high-performance liquid chromatography (HPLC) analysis to identify and quantify phenolic and flavonoid components. In addition, the allelopathic effect of different concentrations of the extract on the germination, seedling growth, and biochemical aspects of bermudagrass was assessed. Our findings showed a significant decrease in bermudagrass seed germination percentage (ranging from 29.6 to 82.4%) and germination index (ranging from 10.07 to 32.43) in response to the extract treatments and a significant decline in all morphological growth parameters of the seedling. HPLC analysis of the extract showed the presence of seven phenolic acids and six flavonoids. The most prevalent phenolics included pyrogallol (13.75 µg/g), ferulic acid (9.82 µg/g), gallic acid (8.5 µg/g), and isoferulic acid (4.47 µg/g), while the predominant flavonoids included catechin (11.04 µg/g), luteolin (8.26 µg/g) and quercetin (7.74 µg/g). The highest extract concentrations (75% and 100%) showed a corresponding decline in the leaf content of chlorophylls a and b but a significant increase in the content of free amino acids, total protein and soluble carbohydrates. Superoxide dismutase (SOD) activity exposed a concentration-dependent reduction, while the activities of both catalase (CAT) and ascorbate peroxidase (APX) were reduced only with the highest extract concentration. The principal component analysis (PCA) showed a high correlation among the morphological growth parameters, indicating that these elements either have a common ground of variance or are inter-correlated. Accordingly, our findings suggest the possibility of combating bermudagrass weeds using the aqueous extract of wheat straw.

The extended day length promotes earlier flowering of bermudagrass.

Day length is a very critical environmental factor affecting plant growth and development. The extension of light application time has been shown to promote flowering in the long-day plant and to shorten breeding time in some crops. However, previous research on the regulation of bermudagrass flowering by light application time is scarce. Therefore, this study investigated the effect of day length on the growth and flowering of bermudagrass by prolonging the light application time in a controlled greenhouse. Three different light application times were set up in the experiment: 22/2 h (22 hours light/2 hours dark), 18/6 h (18 hours light/6 hours dark), 14/10 h (14 hours light/10 hours dark). Results showed that extending the light application time not only promoted the growth of bermudagrass (plant height, fresh weight, dry weight) but also its nutrient uptake (nitrogen (N) and phosphorous (P) content). In addition, daily light integrals were different when flowering under different light application times. Most importantly, under the 22/2 h condition, flowering time was successfully reduced to 44 days for common bermudagrass (Cynodon dactylon [L.] pers) genotype A12359 and 36 days for African bermudagrass (Cynodon transvaalensis Burtt-Davy) genotype ABD11. This study demonstrated a successful method of bermudagrass flowering earlier than usual time by manipulating light application time which may provide useful insights for bermudagrass breeding.

Proteome-wide analyses reveal diverse functions of protein acetylation and succinylation modifications in fast growing stolons of bermudagrass (Cynodon dactylon L.)

BackgroundBermudagrass (Cynodon dactylon L.) is an important warm-season turfgrass species with well-developed stolons, which lay the foundation for the fast propagation of bermudagrass plants through asexual clonal growth. However, the growth and development of bermudagrass stolons are still poorly understood at the molecular level.ResultsIn this study, we comprehensively analyzed the acetylation and succinylation modifications of proteins in fast-growing stolons of the bermudagrass cultivar Yangjiang. A total of 4657 lysine acetylation sites on 1914 proteins and 226 lysine succinylation sites on 128 proteins were successfully identified using liquid chromatography coupled to tandem mass spectrometry, respectively. Furthermore, 78 proteins and 81 lysine sites were found to be both acetylated and succinylated. Functional enrichment analysis revealed that acetylated proteins regulate diverse reactions of carbohydrate metabolism and protein turnover, whereas succinylated proteins mainly regulate the citrate cycle. These results partly explained the different growth disturbances of bermudagrass stolons under treatment with sodium butyrate and sodium malonate, which interfere with protein acetylation and succinylation, respectively. Moreover, 140 acetylated proteins and 42 succinylated proteins were further characterized having similarly modified orthologs in other grass species. Site-specific mutations combined with enzymatic activity assays indicated that the conserved acetylation of catalase and succinylation of malate dehydrogenase both inhibited their activities, further implying important regulatory roles of the two modifications.ConclusionIn summary, our study implied that lysine acetylation and succinylation of proteins possibly play important regulatory roles in the fast growth of bermudagrass stolons. The results not only provide new insights into clonal growth of bermudagrass but also offer a rich resource for functional analyses of protein lysine acetylation and succinylation in plants.

Salt-tolerant endophytic bacterium Enterobacter ludwigii B30 enhance bermudagrass growth under salt stress by modulating plant physiology and changing rhizosphere and root bacterial community.

Osmotic and ionic induced salt stress suppresses plant growth. In a previous study, Enterobacter ludwigii B30, isolated from Paspalum vaginatum, improved seed germination, root length, and seedling length of bermudagrass (Cynodon dactylon) under salt stress. In this study, E. ludwigii B30 application improved fresh weight and dry weight, carotenoid and chlorophyll levels, catalase and superoxide dismutase activities, indole acetic acid content and K+ concentration. Without E. ludwigii B30 treatment, bermudagrass under salt stress decreased malondialdehyde and proline content, Y(NO) and Y(NPQ), Na+ concentration, 1-aminocyclopropane-1-carboxylate, and abscisic acid content. After E. ludwigii B30 inoculation, bacterial community richness and diversity in the rhizosphere increased compared with the rhizosphere adjacent to roots under salt stress. Turf quality and carotenoid content were positively correlated with the incidence of the phyla Chloroflexi and Fibrobacteres in rhizosphere soil, and indole acetic acid (IAA) level was positively correlated with the phyla Actinobacteria and Chloroflexi in the roots. Our results suggest that E. ludwigii B30 can improve the ability of bermudagrass to accumulate biomass, adjust osmosis, improve photosynthetic efficiency and selectively absorb ions for reducing salt stress-induced injury, while changing the bacterial community structure of the rhizosphere and bermudagrass roots. They also provide a foundation for understanding how the bermudagrass rhizosphere and root microorganisms respond to endophyte inoculation.

Phytoremediation potential of Bermuda grass (Cynodon dactylon (L.) pers.) in soils co-contaminated with polycyclic aromatic hydrocarbons and cadmium

Soils co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and cadmium (Cd) have serious environmental impacts and are highly toxic to humans and ecosystems. Phytoremediation is an effective biotechnology for the remediation and restoration of PAH- and Cd-polluted soils. Pot experiments were conducted to investigate the individual and combined effects of PAHs (1238.62 mg kg−1) and Cd (23.1 mg kg−1) on the phytoremediation potential of Bermuda grass grown in contaminated soils. Bermuda grass exhibited a significant decrease in plant growth rate, leaf pigment content, root activity, plant height and biomass and a remarkable increase in malondialdehyde content and electrolyte leakage when grown in PAH- and Cd-contaminated soils compared with grass grown in uncontaminated soils. The activity of soil enzymes, including urease, alkaline phosphatase, sucrose, and fluorescein diacetate hydrolysis, were reduced in soil with PAH and Cd stress. Furthermore, the toxicity of combined PAHs and Cd on Bermuda grass growth and soil enzyme activity was much higher than that of PAH or Cd stress alone, suggesting a synergistic effect of PAHs and Cd on cytotoxicity. To scavenge redundant reactive oxygen species and avoid oxidative damage, Bermuda grass increased plant catalase, superoxide dismutase, and peroxidase activity and soluble sugar and proline content. The bioconcentration factor of Cd in Bermuda grass grown under Cd alone and combined PAH and Cd exposure was greater than 1 for both, suggesting that Bermuda grass has a high Cd accumulation ability. Under PAH alone and combined PAH and Cd exposure conditions, a higher PAH removal rate (41.5–56.8%) was observed in soils planted with Bermuda grass than in unplanted soils (24.8–29.8%), indicating that Bermuda grass has a great ability to degrade PAHs. Bermuda grass showed great phytoremediation potential for the degradation of PAHs and phytoextraction of Cd in co-contaminated soils.

CdWRKY2-mediated sucrose biosynthesis and CBF-signalling pathways coordinately contribute to cold tolerance in bermudagrass.

SummaryBermudagrass (Cynodon dactylon) is one of the most widely cultivated warm‐season turfgrass species around the world. Cold stress has been a key environmental factor that adversely affects the growth, development, and geographical distribution of bermudagrass; however, the underlying mechanism of bermudagrass responsive to cold stress remains largely unexplored. Here, we identified a cold‐induced WRKY transcription factor CdWRKY2 from bermudagrass and demonstrated its function in cold stress response. Overexpression of CdWRKY2 enhanced cold tolerance in transgenic Arabidopsis and bermudagrass hairy roots, while knocking down CdWRKY2 expression via virus‐induced gene silencing increased cold susceptibility. RNA sequencing showed that overexpression of CdWRKY2 in Arabidopsis activated the expression of genes involved in sucrose synthesis and metabolism, including sucrose synthase 1 (AtSUS1) and sucrose phosphate synthase 2F (AtSPS2F). CdSPS1, the homology gene of AtSPS2F in bermudagrass, was subsequently proven to be the direct target of CdWRKY2 by yeast one‐hybrid, electrophoretic mobility shift assay, and transient expression analysis. As expected, overexpression of CdSPS1 conferred cold tolerance in transgenic Arabidopsis plants, whereas silencing CdSPS1 expression enhanced cold sensitivity in bermudagrass. Besides, CdCBF1 whose expression was dramatically up‐regulated in CdWRKY2‐overexpressing bermudagrass hairy roots but down‐regulated in CdWRKY2‐silencing bermudagrass both under normal and cold stress conditions was confirmed as another target of CdWRKY2. Collectively, this study reveals that CdWRKY2 is a positive regulator in cold stress by targeting CdSPS1 and CdCBF1 promoters and activating their expression to coordinately mediate sucrose biosynthesis and CBF‐signalling pathway, which provides valuable information for breeding cold‐resistant bermudagrass through gene manipulation.

Dairy Effluent-Saturated Biochar Alters Microbial Communities and Enhances Bermudagrass Growth and Soil Fertility

Recently, biochar has been proposed for various agronomic applications including improved plant growth and soil fertility. In this study, the effects of dairy effluent-saturated (SBC) and unsaturated wood-derived biochar (UBC) on Bermudagrass (Cynodon spp.) growth, soil fertility and microbial communities were investigated in a greenhouse pot study. SBC and UBC were mixed with sandy loam soil at various loading rates (0, 1, 2, 4, and 8%) to grow Bermudagrass for 10 weeks. Soil physicochemical properties and plant growth measurements were taken, followed by 16S rRNA (V3-V4) amplicon sequencing of soil bacterial communities. Amendment of SBC to soil altered the soil physicochemical properties and increased the concentrations of N and P in the soil at 2 to 8% loading rates compared to UBC treated soil. The addition of SBC to soil also increased the overall plant biomass compared to UBC with more effects on aboveground biomass. Differential abundance analysis of taxa showed enrichment of Proteobacteria in UBC-amended soil, whereas Firmicutes and Nitrospirae were abundant in SBC-amended soil. Interestingly, enrichment of photosynthetic and N-fixing bacteria was observed in both SBC and UBC-amended soils after 10 weeks of treatments. However, oxidative phosphorylation and biotin metabolisms were found to be more abundant in SBC-amended soil compared to UBC-amended soil. Overall, our study suggested that amendment of SBC to soil resulted in enhanced soil nutrients, microbial capacity and Bermudagrass growth than that of UBC. Therefore, application of SBC to soil in field trials would be merited to identify sustainable and effective practices for enhancing plant growth, soil fertility and soil bacterial community.

Identification of Cd-resistant microorganisms from heavy metal-contaminated soil and its potential in promoting the growth and Cd accumulation of bermudagrass

Phytoremediation has been increasingly used as a green technology for the remediation of heavy metal contaminated soils. Microorganisms could enhance phytoremediation efficiency by solubilizing heavy metal and improve plant growth by producing phytohormones in the heavy metal contaminated soils. In this study, we investigated the abundance and composition of soil microbial communities in heavy metal contaminated soils. Furthermore, we identified a Cd-resistant fungal strain Penicillium janthinellum ZZ-2 and assessed its potential in improving plant growth, Cd accumulation and Cd tolerance in bermudagrass. The results indicated that long-term heavy metal pollution decreased microbial biomass and activity by inhibiting microbial community diversity, but did not significantly affect community composition. Mainly, the relative abundance of some specific bacterial and fungal taxa, such as Actinobacteria, Chloroflexi, Bacteroidetes, Ascomycota and Basidiomycota, changes under metal pollution. Furthermore, at genus level, certain microbial taxa, such as Pseudonocardiaceae, AD3, Latescibacteria, Apiotrichum and Paraboeremia, only exist in polluted soil. One Cd-resistant fungus ZZ-2 was isolated and identified as Penicillium janthinellum. Further characterization revealed that ZZ-2 had a greater capacity for Cd2+ absorption, produced indole-3-acid (IAA), and facilitated plant growth in the presence of Cd. Interestingly, ZZ-2 inoculation significantly increased Cd uptake in the stem and root of bermudagrass. Thus, ZZ-2 could improve plant growth under Cd stress by reducing Cd-toxicity, increasing Cd uptake and producing IAA. This study suggests a novel fungus-assisted phytoremediation approach to alleviate Cd toxicity in heavy metals contaminated soils.