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Background Nitrogen (N) is an essential macronutrient that significantly affects turf quality. Commercial cultivars of bermudagrass (Cynodon dactylon (L.) Pers.) require large amounts of nitrogenous fertilizer. Wild bermudagrass germplasm from natural habitats with poor nutrition and diverse N distributions is an important source for low-N-tolerant cultivated bermudagrass breeding. However, the mechanisms underlying the differences in N utilization among wild germplasm resources of bermudagrass are not clear. Results To clarify the low N tolerance mechanism in wild bermudagrass germplasm, the growth, physiology, metabolome and transcriptome of two wild accessions, C291 (low-N-tolerant) and C716 (low-N-sensitive), were investigated. The results showed that root growth was less inhibited in low-N-tolerant C291 than in low-N-sensitive C716 under low N conditions; the root dry weight, soluble protein content and free amino acid content of C291 did not differ from those of the control, while those of C716 were significantly decreased. Down-regulation of N acquisition, primary N assimilation and amino acid biosynthesis was less pronounced in C291 than in C716 under low N conditions; glycolysis and the tricarboxylic acid (TCA) cycle pathway were also down-regulated, accompanied by a decrease in the biosynthesis of amino acids; strikingly, processes such as translation, biosynthesis of the structural constituent of ribosome, and the expression of individual aminoacyl-tRNA synthetase genes, most of genes associated with ribosomes related to protein synthesis were all up-regulated in C291, but down-regulated in C716. Conclusions Overall, low-N-tolerant wild bermudagrass tolerated low N nutrition by reducing N primary assimilation and amino acid biosynthesis, while promoting the root protein synthesis process and thereby maintaining root N status and normal growth.

Centipedegrass [Eremochloa ophiuroides(Munro) Hack.], a member of the Panicoideae subfamily, is one of the most important warm-season turfgrasses originating from China. This grass has an extremely developed prostrate growth habit and has been widely used in transitional and warm climatic regions. To better understand the genetic basis of important biological characteristics, such as prostrate growth and seed yield, in warm-season turfgrasses, we present a high-quality reference genome for centipedegrass and use PacBio, BioNano, and Hi-C technologies to anchor the 867.43 Mb genome assembly into nine pseudochromosomes, with a scaffold N50 of 86.05 Mb and 36,572 annotated genes. Centipedegrass was most closely related to sorghum and diverged from their common ancestor ~16.8 Mya. We detected a novel chromosome reshuffling event in centipedegrass, namely, the nest chromosome fusion event in which fusion of chromosomes 8 and 10 of sorghum into chromosome 3 of centipedegrass likely occurred after the divergence of centipedegrass from sorghum. The typical prostrate growth trait in centipedegrass may be linked to the expansion of candidatePROSTRATE GROWTH 1(PROG1) genes on chromosome 2. Two orthologous genes ofOsPROG1,EoPROG1,andEoPROG2, were confirmed to increase the stem number and decrease the stem angle inArabidopsis. Collectively, our assembled reference genome of centipedegrass offers new knowledge and resources to dissect the genome evolution of Panicoideae and accelerate genome-assisted breeding and improvement of plant architecture in turf plants.

Centipedegrass [Eremochloa ophiuroides (Munro) Hack.] is a perennial warm-season grass that originated in China, and its speed of nodal rooting is important for lawn establishment. In our study, centipedegrass nodal rooting ability was limited by node aging. Transcriptome sequencing of nodal roots after 0, 2, 4, and 8 days of water culture was performed to investigate the molecular mechanisms of root development. GO enrichment and KEGG pathway analyses of DEGs indicated that plant hormone signal transduction and transcription factors might play important roles in centipedegrass nodal root growth. Among them, E3 ubiquitin-protein ligases participated in multiple hormone signal transduction pathways and interacted with transcription factors. Furthermore, an E3 ubiquitin protein ligase EoSINAT5 overexpressed in rice resulted in longer roots and more numerous root tips, while knockout of LOC_Os07g46560 (the homologous gene of EoSINAT5 in rice) resulted in shorter roots and fewer root tips. These results indicated that EoSINAT5 and its homologous gene are able to promote nodal root development. This research presents the transcriptomic analyses of centipedegrass nodal roots, and may contribute to elucidating the mechanism governing the development of nodal roots and facilitates the use of molecular breeding in improving rooting ability.

Cold plasma is a new agricultural technology demonstrating wide potential application in plants. Previous studies have elucidated that the cold plasma pre-treatment of seeds improves seed germination and early growth. However, the effects of cold plasma treatment on vegetative propagation, including rooting, remains unclear. In this study, effects of cold plasma treatment on rooting percentage, physiochemical properties in stolon cuttings and physiological characteristics in the rooting process of centipedegrass (Eremochloa ophiuroides (Munro.) Hack.) stolon cuttings were investigated. The centipedegrass stolon cuttings were pre-treated with 0, 150, 300 and 450 W of cold plasma for 15 s. Cold plasma treatments positively stimulated rooting of stolon cuttings, and the 300 W treatment yielded the best effect. Rooting percentage, numbers of adventitious roots, total root length, total root surface area, total root volume, average root diameter, and dry weights of roots were significantly improved by cold plasma treatments. The conductivity and water uptake increased by cold plasma treatments; the auxin (IAA) content and activities of polyphenol oxidase and peroxidase activities improved, and the IAA-oxidase activity decreased; the soluble sugar and protein contents increased after cold plasma treatment. The results of this study not only showed that cold plasma pre-treatment may improve rooting of vegetations but also provided inspiration and support for the application of cold plasma in vegetative propagation of plant.

Bermudagrass (Cynodon dactylon) is a salinity-tolerant turfgrass that has good use potential in the saline-alkali lands of warm regions. However, the systematic Na+ and K+ regulation mechanisms und...

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Photosynthesis plays a vital role in maintaining vigorous, healthy turf under nitrogen (N)-limiting conditions. The effects of low N stress on the aboveground growth of bermudagrass (Cynodon dactylon (L.) Pers.) as well as its photosynthesis, chlorophyll fluorescence, CO2 assimilation, and carbohydrate pools were studied using hydroponic experiments. Two bermudagrass accessions, Yangjiang (low N tolerant) and C716 (low N sensitive), were used. Low N supply decreased the aboveground dry weight of both accessions. In comparison to C716, Yangjiang maintained better aboveground growth, which was attributed to its smaller reductions in leaf area and the net photosynthetic rate (Pn) at low N conditions. The Pn reduction in both accessions was on account of a reduction in stomatal conductance (Gs) and was partially due to nonstomatal limitations. Furthermore, the smaller Pn reduction in Yangjiang than in C716 was associated with the smaller decrease in CO2 assimilatory capacity in the former, and the ribulose-1,5-bisphosphate carboxylase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC) activities decreased based on leaf protein content. Although the leaf sucrose synthesis capacity and sucrose phosphate synthase (SPS) and sucrose synthase (SS) activities in Yangjiang increased more than those in C716, carbohydrates did not accumulate in the leaves of either accession to repress photosynthesis. This work provides new insights into CO2 assimilatory capacity rather than carbohydrate status under conditions of reduced leaf photosynthesis and decreasing aboveground growth in bermudagrass under low N conditions. Hence, bermudagrass accessions with low N tolerance are excellent sources of turf requiring reduced N fertilizer inputs.

Genetic diversity is the heritable variation within and among populations, and in the context of this paper describes the heritable variation among the germplasm resources of centipedegrass. Centipedegrass is an important warm-season perennial C4 grass belonging to the Poaceae family in the subfamily Panicoideae and genus Eremochloa. It is the only species cultivated for turf among the eight species in Eremochloa. The center of origin for this species is southern to central China. Although centipedegrass is an excellent lawn grass and is most widely used in the southeastern United States, China has the largest reserve of centipedegrass germplasm in the world. Presently, the gene bank in China holds ~200 centipedegrass accessions collected from geographical regions that are diverse in terms of climate and elevation. This collection appears to have broad variability with regard to morphological and physiological characteristics. To efficiently develop new centipedegrass varieties and improve cultivated species by fully utilizing this variability, multiple approaches have been implemented in recent years to detect the extent of variation and to unravel the patterns of genetic diversity among centipedegrass collections. In this review, we briefly summarize research progress in investigating the diversity of centipedegrass using morphological, physiological, cytological, and molecular biological approaches, and present the current status of genomic studies in centipedegrass. Perspectives on future research on genetics and genomics and modern breeding of centipedegrass are also discussed.

Bermudagrass (Cynodon dactylon (L.) Pers.) is a widely used warm-season turfgrass and has the highest nitrogen (N) fertilization requirements among turfgrasses. Wild ecotype found in N-poor habitats can potentially tolerant N limiting conditions for reducing N inputs in the turf industry. However, the extent of variation in their low N tolerance has remained unclear. We conducted hydroponic experiments to evaluate the variation on growth, N accumulation, and partitioning of wild bermudagrass from China pre-core collection under normal (5 mM) and limited (0.05 mM) N levels in two experiments. The results showed that low N nutrition significantly decreased clipping growth, while had no effects on verdure and root growth; in addition, the magnitude of clippings N accumulation reduction was higher than verdure and root across all accessions. However, significant genetic variations in all studied traits except for root N content in experiment 2 were found among accessions. Using a cluster analysis, 56 ...

Background Areas with saline soils are sparsely populated and have fragile ecosystems, which severely restricts the sustainable development of local economies. Zoysia grasses are recognized as excellent warm-season turfgrasses worldwide, with high salt tolerance and superior growth in saline-alkali soils. However, the mechanism underlying the salt tolerance of Zoysia species remains unknown. Results The phenotypic and physiological responses of two contrasting materials, Zoysia japonica Steud. Z004 (salt sensitive) and Z011 (salt tolerant) in response to salt stress were studied. The results show that Z011 was more salt tolerant than was Z004, with the former presenting greater K+/Na+ ratios in both its leaves and roots. To study the molecular mechanisms underlying salt tolerance further, we compared the transcriptomes of the two materials at different time points (0 h, 1 h, 24 h, and 72 h) and from different tissues (leaves and roots) under salt treatment. The 24-h time point and the roots might make significant contributions to the salt tolerance. Moreover, GO and KEGG analyses of different comparisons revealed that the key DEGs participating in the salt-stress response belonged to the hormone pathway, various TF families and the DUF family. Conclusions Zoysia salt treatment transcriptome shows the 24-h and roots may make significant contributions to the salt tolerance. The auxin signal transduction family, ABA signal transduction family, WRKY TF family and bHLH TF family may be the most important families in Zoysia salt-stress regulation.

Leaf tensile strength is an important parameter for evaluating leaf mechanical strength, which is closely related to preference of forage grasses and feel quality of turfgrasses. Although the variance of leaf tensile strength in different forage grass species has been extensively studied, similar information concerning the leaf tensile strength in turfgrasses are still deficient. In this study, the leaf tensile strength of eight cultivars and wild accessions of Cynodon dactylon and Zoysia japonica were determined and compared for the first time. The results indicated that leaf tensile strength are highly variable in different C. dactylon and Z. japonica cultivars and wild accessions. Average value of leaf tensile strength of the eight C. dactylon cultivars and wild accessions are much lower than that of the eight Z. japonica cultivars and wild accessions, suggesting Z. japonica are generally tougher than C. dactylon. In an additional experiment, the effects of irrigation and fertilization on leaf tensile strength of C. dactylon cv. Yangjiang and Z. japonica cv. Crowne were also analyzed. The results indicated that less irrigation and excess fertilization treatment both resulted in a significant reduction of leaf tensile strength of the two turfgrass species, suggesting leaf tensile strength of the turfgrasses under investigation may be altered through a combination of different management measures. This information greatly improves our understanding of leaf mechanical strength of turfgrasses.

Bermudagrass (Cynodon dactylon L.) is a prominent warm-season turf and forage grass species with multiple applications. In most C. dactylon cultivars and accessions, erect-growing stems (shoot) and prostrate-growing stems (stolon) often coexist. These two types of stems are both formed through tillering but grow in two directions with different tiller angles. Elucidating the mechanism of tiller angle regulation in bermudagrass could provide important clues to breed cultivars with different plant architectural features for diverse usage. In this study, we compared the stem internode transcriptome of two bermudagrass wild accessions with extremely different tiller angles and stem growth directions. A total of 2088 and 12,141 unigenes were preferentially expressed in prostrate-growing wild accession C792 and erect-growing wild accession C793, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology-based Annotation System (KOBAS) analyses further indicated that light- and gravity-responsive genes were enriched in accession C792, whereas lignin synthesis-related genes were enriched in accession C793, which well explains the difference in lignification of vascular bundles and mechanical tissues in the two accessions. These results not only expand our understanding of the genetic control of tiller angle and stem growth direction in bermudagrass but also provide insight for future molecular breeding of C. dactylon and other turfgrass species with different plant architectures.

As a widely used turfgrass species, bermudagrass (Cynodon dactylon L.) can be easily propagated through colonial growth of stolons. Previous studies collectively revealed that exotic environmental factors and intrinsic hormones and genes are all involved in the differentiation, development, and diageotropical growth of stolons. However, the detailed molecular mechanism how environmental and hormone signals regulate the gene expression and biochemical activities in bermudagrass stolons remains unclear. In this study, we observed that reversible phosphorylation modification plays important roles in normal growth and physiological functions of bermudagrass stolons. LC-MS/MS analyses of the total protein extracts of bermudagrass stolons without preliminary phosphopeptide-enrichment successfully identified 646 nonredundant phosphorylation sites and 485 phosphoproteins. The phosphoproteins were significantly enriched in protein phosphorylation regulation and starch metabolism processes. Motif-X analyses further revealed that phosphoproteins containing novel phosphorylation motifs might be involved in transcription regulation of bermudagrass stolons. These results greatly expanded our understanding of the growth and development of bermudagrass stolons at the post-translational level.