Whole-genome sequencing of allotetraploid bermudagrass reveals the origin of Cynodon and candidate genes for salt tolerance.

Bermudagrass (Cynodon dactylon) is a globally distributed, extensively used warm-season turf and forage grass with high tolerance to salinity and drought stress in alkaline environments. However, the origin of the species and genetic mechanisms for salinity tolerance in the species are basically unknown. Accordingly, we set out to study evolution divergence events in the Cynodon genome and to identify genes for salinity tolerance. We developed a 604.0 Mb chromosome-level polyploid genome sequence for bermudagrass 'A12359' (n = 18). The C. dactylon genome comprises 2 complete sets of homoeologous chromosomes, each with approximately 30 000 genes, and most genes are conserved as syntenic pairs. Phylogenetic study showed that the initial Cynodon species diverged from Oropetium thomaeum approximately 19.7-25.4 million years ago (Mya), the A and B subgenomes of C. dactylon diverged approximately 6.3-9.1 Mya, and the bermudagrass polyploidization event occurred 1.5 Mya on the African continent. Moreover, we identified 82 candidate genes associated with seven agronomic traits using a genome-wide association study, and three single-nucleotide polymorphisms were strongly associated with three salt resistance genes: RAP2-2, CNG channels, and F14D7.1. These genes may be associated with enhanced bermudagrass salt tolerance. These bermudagrass genomic resources, when integrated, may provide fundamental insights into evolution of diploid and tetraploid genomes and enhance the efficacy of comparative genomics in studying salt tolerance in Cynodon.

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.

A comprehensive assessment of photosynthetic acclimation to shade in C4 grass (Cynodon dactylon (L.) Pers.).

BACKGROUND: Light deficit in shaded environment critically impacts the growth and development of turf plants. Despite this fact, past research has predominantly concentrated on shade avoidance rather than shade tolerance. To address this, our study examined the photosynthetic adjustments of Bermudagrass when exposed to varying intensities of shade to gain an integrative understanding of the shade response of C4 turfgrass. RESULTS: We observed alterations in photosynthetic pigment-proteins, electron transport and its associated carbon and nitrogen assimilation, along with ROS-scavenging enzyme activity in shaded conditions. Mild shade enriched Chl b and LHC transcripts, while severe shade promoted Chl a, carotenoids and photosynthetic electron transfer beyond QA- (ET0/RC, φE0, Ψ0). The study also highlighted differential effects of shade on leaf and root components. For example, Soluble sugar content varied between leaves and roots as shade diminished SPS, SUT1 but upregulated BAM. Furthermore, we observed that shading decreased the transcriptional level of genes involving in nitrogen assimilation (e.g. NR) and SOD, POD, CAT enzyme activities in leaves, even though it increased in roots. CONCLUSIONS: As shade intensity increased, considerable changes were noted in light energy conversion and photosynthetic metabolism processes along the electron transport chain axis. Our study thus provides valuable theoretical groundwork for understanding how C4 grass acclimates to shade tolerance.

Optimizing irrigation and nitrogen addition to balance grassland biomass production with greenhouse gas emissions: A mesocosm study.

Achieving a balance between greenhouse gas mitigation and biomass production in grasslands necessitates optimizing irrigation frequency and nitrogen addition, which significantly influence grassland productivity and soil nitrous oxide emissions, and consequently impact the ecosystem carbon dioxide exchange. This study aimed to elucidate these influences using a controlled mesocosm experiment where bermudagrass (Cynodon dactylon L.) was cultivated under varied irrigation frequencies (daily and every 6 days) with (100 kg ha-1) or without nitrogen addition; measurements of net ecosystem carbon dioxide exchange, ecosystem respiration, soil respiration, and nitrous oxide emissions across two cutting events were performed as well. The findings revealed a critical interaction between water-filled pore space, regulated by irrigation, and nitrogen availability, with the latter exerting a more substantial influence on aboveground biomass growth and ecosystem carbon dioxide exchange than water availability. Moreover, the total dry matter was significantly higher with nitrogen addition compared to without nitrogen addition, irrespective of the irrigation frequency. In contrast, soil nitrous oxide emissions were observed to be significantly higher with increased irrigation frequency and nitrogen addition. The effects of nitrogen addition on soil respiration components appeared to depend on water availability, with autotrophic respiration seeing a significant rise with nitrogen addition under limited irrigation (5.4 ± 0.6 µmol m-2 s-1). Interestingly, the lower irrigation frequency did not result in water stress, suggesting resilience in bermudagrass. These findings highlight the importance of considering interactions between irrigation and nitrogen addition to optimize water and nitrogen input in grasslands for a synergistic balance between grassland biomass production and greenhouse gas emission mitigation.

Environmental and Edaphic Factors that Influence Spring Dead Spot Epidemics.

Spring dead spot (SDS) (Ophiosphaerella spp.) is a soilborne disease of warm-season turfgrasses grown where winter dormancy occurs. The edaphic factors that influence where SDS epidemics occur are not well defined. A study was conducted during the spring of 2020 and repeated in the spring of 2021 on four 'TifSport' hybrid bermudagrass (Cynodon dactylon × transvaalensis) golf course fairways expressing SDS symptoms in Cape Charles, VA, U.S.A. SDS within each fairway was mapped from aerial imagery collected in the spring of 2019 with a 20 MP CMOS 4k true color sensor mounted on a DJI Phantom 4 Pro drone. Three disease intensity zones were designated from the maps (low, moderate, high) based on the density of SDS patches in an area. Disease incidence and severity, soil samples, surface firmness, thatch depth, and organic matter measurements were taken from 10 plots within each disease intensity zone from each of the four fairways (n = 120). Multivariate pairwise correlation analyses (P < 0.1) and best subset stepwise regression analyses were conducted to determine which edaphic factors most influenced the SDS epidemic within each fairway and each year. Edaphic factors that correlated with an increase in SDS or were selected for the best fitting model varied across holes and years. However, in certain cases, soil pH and thatch depth were predictors for an increase in SDS. No factors were consistently associated with SDS occurrence, but results from this foundational study of SDS epidemics can guide future research to relate edaphic factors to SDS disease development.

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 48 h after detaching witch's brooms, and adult mites survived an average of 5.6 h 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.

Evaluation of zinc tolerance and accumulation in eight cultivars of bermudagrass (Cynodon spp.): implications for zinc phytoremediation.

Zinc (Zn) is a vital element for plant growth and development, however, excessive Zn is toxic to plants. Common bermudagrass (Cynodon dactylon (L.) Pers.) and hybrid bermudagrass (C. dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) are widely used turfgrass species with strong tolerance to diverse abiotic stresses, including excessive Zn2+ stress. However, the variation of zinc tolerance and accumulation in different bermudagrass cultivars remain unclear. In this study, we systematically analyzed the growth performance, physiological index and ion concentration in eight commercial cultivars of common and hybrid bermudagrass under different concentration of Zn2+ treatments using pot experiments. The results indicated that four cultivars of common bermudagrass could tolerate 20 mM Zn2+, whereas four cultivars of hybrid bermudagrass could only tolerate 10 mM Zn2+. Among the four common bermudagrass cultivars, cultivar Guanzhong and Common showed stronger Zn tolerance and accumulation abilities than other two cultivars. Further analyses of the expression of selected Zn homeostasis-related genes indicated that bermudagrass cultivars with stronger tolerance to excessive Zn have at least one expression-elevated gene involved in Zn homeostasis. These results not only expanded our understanding of Zn tolerance and accumulation in bermudagrass but also facilitated the application of commercial bermudagrass cultivars in phytoremediation of Zn pollution.

Leaf Cuticular Waxes of Bermudagrass Response to Environment-Driven Adaptations of Climate Effect Inferred from Latitude and Longitude Gradient in China.

Bermudagrass (Cynodon dactylon) is a widely used warm season lawn grass. Cuticular wax covering the surface of plant leaves plays an important role in helping plants resist biotic and abiotic stresses. We analyzed the changes of cuticle wax in 25 bermudagrass populations from different longitude and latitude gradients, in order to verify how environmental conditions affect the structure and chemical composition of cuticle wax. Five wax components were identified, including alkanes, esters, alkenes, aldehydes and primary alcohols. The wax characteristics were divided into two principal components, explaining 58.2 % and 66.7 % of the total variability in latitude and longitude, even some populations had a certain correlation with each other. Pearson correlation analysis further showed that the total wax coverage, wax component content and antioxidant enzyme activity of bermudagrass populations on the latitudinal gradient had different responses to environmental factors. Finally, nineteen key genes involved in wax biosynthesis, redox and photosynthesis were identified and verified by RT-qPCR. The results showed that the responses of bermudagrass in different populations to climate change were quite different, which was of great significance for the evolution of bermudagrass populations.

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.

Enhanced Escherichia coli removal from stormwater with bermudagrass-derived activated biochar filtration systems.

Stormwater treatment and reuse can alleviate water pollution and scarcity while current sand filtration systems showed low treatment performance for stormwater. For enhancing E. coli removal in stormwater, this study applied the bermudagrass-derived activated biochars (BCs) in the BC-sand filtration systems for E. coli removal. Compared with the pristine BC (without activation), the FeCl3 and NaOH activations increased the BC carbon content from 68.02% to 71.60% and 81.22% while E. coli removal efficiency increased from 77.60% to 81.16% and 98.68%, respectively. In all BCs, the BC carbon content showed a highly positive correlation with E. coli removal efficiency. The FeCl3 and NaOH activations also led to the enhancement of roughness of BC surface for enhancing E. coli removal by straining (physical entrapment). The main mechanisms for E. coli removal by BC-amended sand column were found to be hydrophobic attraction and straining. Additionally, under 105-107 CFU/mL of E. coli, final E. coli concentration in NaOH activated BC (NaOH-BC) column was one order of magnitude lower than those in pristine BC and FeCl3 activated BC (Fe-BC) columns. The presence of humic acid remarkably lowered the E. coli removal efficiency from 77.60% to 45.38% in pristine BC-amended sand column while slightly lowering the E. coli removal efficiencies from 81.16% and 98.68% to 68.65% and 92.57% in Fe-BC and NaOH-BC-amended sand columns, respectively. Moreover, compared to pristine BC, the activated BCs (Fe-BC and NaOH-BC) also resulted in the lower antibiotics (tetracycline and sulfamethoxazole) concentrations in the effluents from the BC-amended sand columns. Therefore, for the first time, this study indicated NaOH-BC showed high potential for effective treatment of E. coli from stormwater by the BC-amended sand filtration system compared with pristine BC and Fe-BC.

Effects of different water conditions on the biomass, root morphology and aerenchyma formation in bermudagrass (Cynodon dactylon (L.) Pers).

BACKGROUND: The bermudagrass (Cynodon dactylon (L.) Pers) roots responded differently in terms of morphological and anatomical characteristics under diverse submergence conditions, and they developed aerenchyma under non-flooding condition. In order to understand these mechanisms, bermudagrass cuttings were used as experimental material to examine their biomass, root morphology, and aerenchyma formation under three different water treatments, including control (CK), shallow submergence (SS), and deep submergence (DS). RESULTS: The total root length, root volume, root surface area, and biomass of bermudagrass were largest in CK, followed by SS and DS. However, the average root diameter was greater in each of DS and SS than that in CK. Root aerenchyma formation was observed in CK, and submergence boosted the aerenchyma formation and the root cavity rate. Furthermore, our study found that the process of aerenchyma formation began with the increase of cell volume and cell separation to form a narrow space, and these cells gradually died to form matured aerenchyma cavity, which belongs to schizo-lysigenous aerenchyma. Meanwhile, typical biomarkers of programmed cell death were also observed. CONCLUSION: Overall, these results suggested that submergence inhibited the accumulation of biomass and root growth, but facilitated aerenchyma formation by increasing root diameter.

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

BACKGROUND: Bermudagrass (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. RESULTS: In 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. CONCLUSION: In 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.

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

Bermudagrass (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.

Comparative analysis reveals chromosome number reductions in the evolution of African bermudagrass (Cynodon transvaalensis Burtt-Davy).

African bermudagrass (Cynodon transvaalensis Burtt-Davy) (2n = 2x = 18) belongs to the genus Cynodon, tribe Cynodonteae, subfamily Chloridoideae in the grass family Poaceae. The species is frequently crossed with common bermudagrass (Cynodon dactylon Pers.) in developing high-quality hybrid turf cultivars. Molecular resources for C. transvaalensis are scarce; thus, its genomic evolution is unknown. Recently, a linkage map consisting of 1278 markers provided a powerful tool for African bermudagrass genomic research. The objective of this study was to investigate chromosome number reduction events that resulted in the nine haploid chromosomes in this species. Tag sequences of mapped single nucleotide polymorphism markers in C. transvaalensis were compared against genome sequences of Oropetium thomaeum (L.f.) Trin. (2n = 2x = 20), a genomic model in the Cynodonteae tribe. The comparative genomic analyses revealed broad collinearity between the genomes of these two species. The analyses further revealed that two major interchromosomal rearrangements of the paleochromosome ρ12 (ρ1-ρ12-ρ1 and ρ6-ρ12-ρ6) resulted in nine chromosomes in the genome of C. transvaalensis. The findings provide novel information regarding the formation of the initial diploid species in the Cynodon genus.

Physiological integration between Bermudagrass ramets improves overall salt resistance under heterogeneous salt stress.

Connected ramets of colonal plants often suffer from different environmental conditions such as light, nutrient, and stress. Colonal Bermudagrass (Cynodon dactylon [L.] Pers.) can form interconnected ramets and this connection facilitates the tolerance to abiotic stress, which is a kind of physiological integration. However, how bermudagrass responds to heterogeneously distributed salt stress needs to be further elucidated. Here, we demonstrated that severance of stolons aggravated the damage of salt-stressed ramets, displaying higher relative electrolytic leakage (EL), lower content of chlorophyll, higher accumulation of Na+ , and serious oxidative damages. This finding implied the positive effects of the physiological integration of bermudagrass on salt tolerance. The unstressed ramets connected with the stressed one were mildly injured, implying the supporting and sacrifice function of the unstressed ramets. Physiological integration did not mediate the translocation of Na+ among ramets, but induced a higher expression of salt overly sensitive (SOS) genes in the stressed ramets, consequently reducing the accumulation of Na+ in leaves and roots. In addition, physiological integration upregulated the genes expression and enzymes activity of catalase (CAT) and peroxidase (POD) in both stressed and unstressed ramets. This granted a stronger antioxidant ability of the whole clonal plants under salt stress. Enhanced Na+ transfer and increased reactive oxygen species (ROS) scavenging are mechanisms that likely contribute to the physiological integration leading to the salt tolerance of bermudagrass.

Genetic manipulation of bermudagrass photosynthetic biosynthesis using Agrobacterium-mediated transformation.

Bermudagrass is one of the most extensively used warm-season grasses. It is widely used in landscaping, stadium construction and soil remediation due to its excellent regeneration, trampling and stress tolerances. However, studies on its regulatory mechanism and variety improvement by genetic engineering are still at a standstill, owing to its genetic variability and intrinsic limits linked with some resistance to Agrobacterium infection. In this study, we established a higher efficient Agrobacterium-mediated transformation via screening for vital embryogenic callus and improving infection efficiency. The superior callus was light yellow, hard granular and compact, determined with a differentiation rate of more than 95%. The optimized infestation courses by gentle shaking, vacuuming and sonicating were used. The infested calluses were co-cultured for 3 days, followed by desiccation treatments for 1 day to get higher infection efficiency. Then the CdHEMA1 gene, essential for chlorophyll biosynthesis, was cloned and transferred into bermudagrass to validate the aforementioned optimization procedures integrally. Molecular-level analyses indicated that the CdHEMA1 gene had successfully integrated and was greatly increased in transgenic seedlings. Results of the photosynthetic capacity assessment showed that CdHEMA1 overexpression may considerably enhance the contents of photosynthetic pigments, OJIP curve and reaction center density (RC/CSo) to absorb (ABS/CSo, ABS/CSM) and capture (TRo/CSo) more light energy, hence improve the performance indices PIABS and PICS compared to the wild type. The successful completion of this project would provide a solid platform for further gene function study and molecular breeding of bermudagrass.

Bermuda grass latent virus in Australia: genome sequence, sequence variation, and new hosts.

Bermuda grass latent virus (BGLV; genus Panicovirus) is identified for the first time in Australia and in only the second country after the USA. A full-length genome sequence was obtained, which has 97% nucleotide sequence identity to that of the species exemplar isolate. Surveys for BGLV, utilising a newly designed universal panicovirus RT-PCR assay for diagnosis, demonstrated widespread infection by this virus in a broad variety of Bermuda grass cultivars (Cynodon dactylon and C. dactylon × C. transvaalensis) grown in both New South Wales and Queensland. The virus was also detected in Rhodes grass (Chloris gayana) and Kikuyu grass (Cenchrus clandestinus), which are both important pasture grasses in subtropical Australia, and the latter is also grown as turf. Furthermore, the Rhodes grass plant, which had strong mosaic symptoms, was also infected with sugarcane mosaic virus, warranting further investigations as to whether synergistic interactions occur between these two viruses.

Plant growth promoting strain Bacillus cereus (RCS-4 MZ520573.1) enhances phytoremediation potential of Cynodon dactylon L. in distillery sludge.

Elevated levels of physico-chemical pollution including organic pollutants, metals and metalloids were detected in distillery sludges despite of the anaerobic digestion treatment prior to disposal. The concentrations of the metals were (in mg kg-1): Fe (400.98 ± 3.11), Zn (17.21 ± 0.54), Mn (8.32 ± 0.42), Ni (8.00 ± 0.98), Pb (5.09 ± 0.43), Cr (4.00 ± 0.98), and Cu (3.00 ± 0.10). An invasive grass species, Cynodon dactylon L., demonstrated its ability to remediate the distillery waste sludge (DWS) in the field study. All the physico-chemical parameters of the sludge significantly improved (up to 70-75%) in the presence of Cynodon dactylon L. (p < 0.001) than the control with no plant growth. The highest phytoremediation capacity was associated with the uptake of Fe in the root and shoot. Sludge samples collected near the rhizosphere also showed lower amount of organic compounds compared to control sludge samples. Metal resistant Bacillus cereus (RCS-4 MZ520573.1) was isolated from the rhizosphere of Cynodon dactylon L. and showed potential to enhance the process of phytoremediation via plant growth promoting activities such as production of high level of ligninolytic enzymes: manganese peroxidase (35.98 U), lignin peroxidase (23.98 U) and laccase (12.78 U), indole acetic acid (45.87(mgL-1), phosphatase activity (25.76 mg L-1) and siderophore production (23.09 mg L-1). This study presents information on the performance of Cynodon dactylon L., an abundant invasive perennial grass species and its associated plant growth promoting rhizobacteria demonstrated good capacity to remediate and restore contaminated soil contained complex organic and inorganic pollutants, they could be integrated into the disposal system of distillery sludge to improve the treatment efficiency.

Characterization and Aggressiveness of Take-All Root Rot Pathogens Isolated from Symptomatic Bermudagrass Putting Greens.

Take-all root rot is a disease of ultradwarf bermudagrass putting greens caused by Gaeumannomyces graminis (Gg), Gaeumannomyces sp. (Gx), Gaeumannomyces graminicola (Ggram), Candidacolonium cynodontis (Cc), and Magnaporthiopsis cynodontis (Mc). Many etiological and epidemiological components of this disease remain unknown. Improving pathogen identification and our understanding of the aggressiveness of these pathogens along with growth at different temperatures will advance our knowledge of disease development to optimize management strategies. Take-all root rot pathogens were isolated from symptomatic bermudagrass root and stolon pieces from 16 different golf courses. Isolates of Gg, Gx, Ggram, Cc, and Mc were used to inoculate 'Champion' bermudagrass in an in planta aggressiveness assay. Each pathogen was also evaluated at 10, 15, 20, 25, 30, and 35°C to determine growth temperature optima. Infected plant tissue was used to develop a real-time PCR high-resolution melt assay for pathogen detection. This assay was able to differentiate each pathogen directly from infected plant tissue using a single primer pair. In general, Ggram, Gg, and Gx were the most aggressive while Cc and Mc exhibited moderate aggressiveness. Pathogens were more aggressive when incubated at 30°C compared with 20°C. While they grew optimally between 24.4 and 27.8°C, pathogens exhibited limited growth at 35°C and no growth at 10°C. These data provide important information on this disease and its causal agents that may improve take-all root rot management.

Endophytic bacteria promote biomass production and mercury-bioaccumulation of Bermuda grass and Indian goosegrass.

Plant growth-promoting endophytic bacteria can potentially improve the biomass production of Hg-accumulating grasses, resulting in improved Hg extraction from contaminated soils. This study aimed to analyze the effect of inoculation of Hg-resistant endophytic bacteria (i) Jeotgalicoccus huakuii (B1) and (ii) Bacillus amyloliquefaciens (B2), as single and consortium inoculant, on biomass production and Hg bioaccumulation of Bermuda grass (R1) and Indian goosegrass (R2) planted as monoculture and mixed cropping. The grass seeds were surface-sterilized before the inoculation. Both inoculated seeds with B1 and B2 (treatments) and uninoculated seeds were sown separately in sterilized sand. Grass seedlings of both treatments and control were replanted in the washed and sterilized sand medium, spiked with HgCl2 (100 mg kg-1). A subset of grass was harvested at 0, 4, 6, and 10 weeks after planting to measure biomass production and Hg bioaccumulation. The results showed that bacterial inoculation enhanced the grass biomass by 52.68% and Hg bioaccumulation by 47.76%. Mercury residue of Hg-spiked sand treated with the bacterial consortium was reduced by 80%. This suggests that endophytic bacteria can improve grass biomass production and enhance Hg bioaccumulation in grass biomass.