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Background Poa pratensis  is a predominant cool-season turfgrass utilized in urban landscaping and ecological management. It is extensively employed in turf construction and in the regulation of ecological environments. However, it is susceptible to powdery mildew, a prevalent disease in humid regions. Currently, the primary control measure for powdery mildew involves the application of pesticides, a practice that is both costly and environmentally detrimental. Developing superior disease-resistant cultivars represents a more cost-effective and sustainable strategy for managing turfgrass diseases. Furthermore, an in-depth investigation into the response mechanisms of P. pratensis to powdery mildew infection could significantly advance research on the identification of disease resistance genes and the molecular breeding of resistant varieties. Results In this study, we first assessed the disease incidence across various disease-resistant P. pratensis cultivars and subsequently examined alterations in their in vivo redox states. We employed isobaric tags for relative and absolute quantification (iTRAQ) proteomics alongside non-targeted metabolomics to elucidate the response mechanisms of P. pratensis to powdery mildew invasion. A comprehensive analysis of the shared KEGG pathways among differentially abundant proteins (DAPs) and differentially enriched metabolites (DEMs) led to the identification of four common KEGG pathways. Notably, the phenylpropanoid biosynthesis pathway, enriched in both examined P. pratensis cultivars, was selected for further investigation. This analysis indicated that lignin biosynthesis plays a crucial role in the response of P. pratensis to powdery mildew infection. Conclusions The findings of this study enhance our understanding of the mechanisms underlying powdery mildew resistance in P. pratensis and serve as a valuable reference for the selection of powdery mildew-resistant cultivars, as well as for the identification and application of associated disease resistance genes. Clinical trial number Not applicable.

Background Kentucky bluegrass ( Poa pratensis L.) panicle development is a coordinated process of cell proliferation and differentiation with distinctive phases and architectural changes that are pivotal to determine seed yield. Cytokinin (CK) is a key factor in determining seed yield that might underpin the second “Green Revolution”. However, whether there is a difference between endogenous CK content and seed yields of Kentucky bluegrass, and how CK-related genes are expressed to affect enzyme regulation and downstream seed yield in Kentucky bluegrass remains enigmatic. Results In order to establish a potential link between CK regulation and seed yield, we dissected and characterized the Kentucky bluegrass young panicle, and determined the changes in nutrients, 6 types of endogenous CKs, and 16 genes involved in biosynthesis, activation, inactivation, re-activation and degradation of CKs during young panicle differentiation of Kentucky bluegrass. We found that high seed yield material had more meristems compared to low seed yield material. Additionally, it was found that seed-setting rate (SSR) and lipase activity at the stage of spikelet and floret primordium differentiation (S3), as well as 1000-grain weight (TGW) and zeatin-riboside (ZR) content at the stages of first bract primordium differentiation (S1) and branch primordium differentiation (S2) showed a significantly positive correlation in the two materials. And zeatin, ZR, dihydrozeatin riboside, isopentenyl adenosine and isopentenyl adenosine riboside contents were higher in seed high yield material than those in seed low yield material at S3 stage. Furthermore, the expressions of PpITP3 , PpITP5 , PpITP8 and PpLOG1 were positively correlated with seed yield, while the expressions of PpCKX2 , PpCKX5 and PpCKX7 were negatively correlated with seed yield in Kentucky bluegrass. Conclusions Overall, our study established a relationship between CK and seed yield in Kentucky bluegrass. Perhaps we can increase SSR and TGW by increasing lipase activity and ZR content. Of course, using modern gene editing techniques to manipulate CK related genes such as PpITP3/5/8 , PpLOG1 and PpCKX2/5/7 , will be a more direct and effective method in Kentucky bluegrass, which requires further trial validation.

Background Rhizome is vital for carbon and nitrogen metabolism of the whole plant. However, the effect of carbon and nitrogen in the rhizome on rhizome expansion remains unclear. Results Three wild Kentucky bluegrass ( Poa pratensis L.) germplasms with different rhizome expansion capacity (strong expansion capacity, ‘YZ’; medium expansion capacity, ‘WY’; and weak expansion capacity, ‘AD’) were planted in the field and the rhizomes number, tiller number, rhizome dry weight, physiological indicators and enzyme activity associated carbon and nitrogen metabolisms were measured. Liquid chromatography coupled to mass spectrometry (LC-MS) was utilized to analyze the metabolomic of the rhizomes. The results showed that the rhizome and tiller numbers of the YZ were 3.26 and 2.69-fold of that of the AD, respectively. The aboveground dry weight of the YZ was the greatest among all three germplasms. Contents of soluble sugar, starch, sucrose, NO 3 − -N, and free amino acid were significantly higher in rhizomes of the YZ than those of the WY and AD ( P  < 0.05). The activities of glutamine synthetase (GS), glutamate dehydrogenase (GDH) and sucrose phosphate synthase (SPS) of the YZ were the highest among all three germplasm, with values of 17.73 A·g − 1  h − 1 , 5.96 µmol·g − 1  min − 1 , and 11.35 mg·g − 1  h − 1 , respectively. Metabolomics analyses revealed that a total of 28 differentially expressed metabolites (DEMs) were up-regulated, and 25 DEMs were down-regulated in both comparison groups (AD vs. YZ group and WY vs. YZ group). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis demonstrated that metabolites related to histidine metabolism, tyrosine metabolism, tryptophan metabolism, and phenylalanine metabolism were associated with rhizomes carbon and nitrogen metabolism. Conclusions Overall, the results suggest that soluble sugar, starch, sucrose, NO 3 − -N, and free amino acid in rhizome are important to and promote rhizome expansion in Kentucky bluegrass, while tryptamine, 3-methylhistidine, 3-indoleacetonitrile, indole, and histamine may be key metabolites in promoting carbon and nitrogen metabolism of rhizome.

Kentucky bluegrass ( Poa pratensis L.), a native grass species of the Qinghai-Tibetan Plateau, is widely used for ecological restoration due to its high growth rate and strong adaptability. However, monocultures of Poa pratensis are prone to rapid degradation and low productivity, limiting their suitability for animal husbandry. To address these challenges, this study evaluated the production performance and interspecific relationships of different mixed-sown and monoculture grasslands to identify optimal cultivation strategies. Field experiments were conducted over a six-year period, with three mixed-sown treatments— Poa pratensis combined with Siberian wildrye ( Elymus sibiricus L.), Chinese fescue ( Festuca sinensis Engler ex S.L.Lu), and alkali grass ( Puccinellia tenuiflora (Griseb.) Scribn. & Merr.)—alongside their respective monocultures. LASSO regression (Least Absolute Shrinkage and Selection Operator Regression) and ROC curve analysis (Receiver Operating Characteristic Curve Analysis) were applied to identify key factors influencing production performance. The results indicated that the mixed-sown grassland of Elymus sibiricus and Poa pratensis significantly boosted forage yield by 216.88% to 323.06% in comparison with monoculture Poa pratensis . Additionally, the comprehensive evaluation index, which integrates forage yield and nutritional quality, was 16.41% higher for the Elymus sibiricus and Poa pratensis mixture than for the monoculture Poa pratensis grassland. These findings imply that the mixed-sown grassland of Elymus sibiricus and Poa pratensis effectively addresses the low productivity issue often seen in monoculture Poa pratensis grasslands. However, in terms of yield stability and interspecific compatibility, the mixed-sown grassland of Puccinellia tenuiflora and Poa pratensis demonstrated superior performance. Its relative total yield (RTY) consistently exceeded 1.0 from the third to the sixth year, reflecting higher interspecific compatibility and stable productivity over time. And the Poa pratensis and Puccinellia tenuiflora mixture showed the best performance, achieving the highest stability value of 3.12. Therefore, the combination of Poa pratensis and Puccinellia tenuiflora is recommended as the optimal strategy for achieving long-term yield stability and high productivity in cultivated grasslands.

As the Latin name annua implies, the species Poa annua L. is thought to have an annual life cycle. Yet, there are many reports in literature of P . annua persisting as a perennial. Considering that P . annua senescence patterns do not align with other true annual species, we hypothesized that P . annua is similar to other perennial, C 3 turfgrass species that are subject to a confluence of environmental factors that can cause mortality. Four experiments were conducted in Knoxville, TN with the objective of determining environmental factors lethal to P . annua . A field monitoring study assessed 100 P . annua plants across ten grassland micro-environments from May to October 2020. Forty plants survived the summer and confirmed the existence of perennial P . annua ecotypes. Analysis of environmental factors at the time of plant death indicated soil moisture, soil temperature, and pathogenic infection were associated with mortality. A series of glasshouse or field experiments were conducted to investigate the effects of each factor on P . annua mortality. Soil moisture and soil temperature were not lethal to P . annua in the glasshouse, except under extreme conditions not typical in the field. A field study assessed mortality of plants from pathogenic infection and indicated that P . annua plants treated with fungicide throughout the summer survived year-round, whereas plants not receiving fungicide applications senesced. These findings support our hypothesis that P . annua is of a perennial life cycle, which can be influenced by environmental conditions. We suggest that the name P . annua is likely a misnomer based on its modern interpretation.

Background Poa annua (annual bluegrass) is an allotetraploid turfgrass, an agronomically significant weed, and one of the most widely dispersed plant species on earth. Here, we report the chromosome-scale genome assemblies of P. annua’s diploid progenitors, P. infirma and P. supina, and use multi-omic analyses spanning all three species to better understand P. annua’s evolutionary novelty. Results We find that the diploids diverged from their common ancestor 5.5 – 6.3 million years ago and hybridized to form P. annua  ≤ 50,000 years ago. The diploid genomes are similar in chromosome structure and most notably distinguished by the divergent evolutionary histories of their transposable elements, leading to a 1.7 × difference in genome size. In allotetraploid P. annua, we find biased movement of retrotransposons from the larger (A) subgenome to the smaller (B) subgenome. We show that P. annua’s B subgenome is preferentially accumulating genes and that its genes are more highly expressed. Whole-genome resequencing of several additional P. annua accessions revealed large-scale chromosomal rearrangements characterized by extensive TE-downsizing and evidence to support the Genome Balance Hypothesis. Conclusions The divergent evolutions of the diploid progenitors played a central role in conferring onto P. annua its remarkable phenotypic plasticity. We find that plant genes (guided by selection and drift) and transposable elements (mostly guided by host immunity) each respond to polyploidy in unique ways and that P. annua uses whole-genome duplication to purge highly parasitized heterochromatic sequences. The findings and genomic resources presented here will enable the development of homoeolog-specific markers for accelerated weed science and turfgrass breeding .

Background Poa pratensis L. is a perennial grass commonly used for ecological restoration due to its rapid growth rate and strong adaptability. It is considered an excellent choice for soccer fields and urban green spaces because of its high wear resistance and durability. this is the first report demonstrating the co-application of seed priming and plasma-activated water irrigation for enhancing drought resistance in P. pratensis . This study aimed to examine the influence of seed priming and irrigation with PAW on the growth of P. pratensis and its ability to endure drought conditions. The experiment was conducted in a greenhouse in 2023, using a completely randomized design. Seeds were primed with either normal water (control group) or PAW and then sown in pots containing standard soil. The experiment included six treatments: three PAW management strategies—watered normally (WW, control group), seeds primed with PAW and irrigated with normal water (PW), and a combination of both methods (PP: primed and irrigated with PAW)—under both drought and non-drought stress conditions. Results The findings indicated that drought stress significantly decreased various growth parameters, including fresh weight (21% reduction), dry weight (27% reduction), chlorophyll levels (12% reduction), and the activities of the enzymes ascorbate peroxidase (APX) and catalase (CAT) (22% and 5% reductions, respectively) in P. pratensis . Conversely, drought stress increased the levels of several compounds: carotenoids (24% increase), malondialdehyde (MDA) (81% increase), proline (80% increase), soluble carbohydrates (15% increase), and the enzyme activity of guaiacol peroxidase (GPX) (36% increase). Under drought conditions, seed priming with PAW led to a decrease in MDA (21%) and an increase in fresh weight (approximately 13%) and dry weight (about 25%). Total chlorophyll increased by around 30%, while proline and soluble sugar content rose by 14% and 50%, respectively. The activities of APX, CAT, and GPX enzymes increased by 18%, 4%, and 11%, respectively. In summary, the combination of seed priming and irrigation with PAW under drought conditions reduced MDA content by 28% and enhanced plant biomass (fresh weight by 13% and dry weight by 21%), photosynthetic pigments (total chlorophyll by 17%), and osmoprotectants (proline by 56% and soluble carbohydrates by 11%). The activities of APX, CAT, and GPX also increased significantly—by 16%, 2%, and 16%, respectively. Conclusions PAW has been shown to improve drought stress in P. pratensis by reducing lipid peroxidation and increasing levels of photosynthetic pigments, osmoprotectants, and antioxidant enzyme activity. The results indicate that the most beneficial outcomes occur when seed priming is combined with PAW irrigation. This technology could serve as a cost-effective and sustainable method for enhancing growth and drought tolerance in plants, including P. pratensis , under water-stressed conditions. Further studies are necessary to explore this effect on additional plants and to better understand its details and possible mechanisms in future research.

Kentucky bluegrass (Poa pratensis L.) is an important cool season turfgrass species with a high cold tolerance, but it is sensitive to drought. It is valuable for the applications of Kentucky bluegrass to improve its drought tolerance. However, little is known about the underlying drought mechanism. In the present study, transcriptomic profiling in the roots and leaves of the Kentucky bluegrass cultivar ‘Qinghai’, in response to osmotic stress in the form of treatment with 2 h and 50 h of 25% (v/v) PEG-6000, was analyzed. The results showed that a large number of genes were significantly up-regulated or down-regulated under osmotic stress. The majority of genes were up-regulated in leaves but down-regulated in roots after 2 h and 50 h of osmotic stress, among them were 350 up-regulated DEGs and 20 down-regulated DEGs shared in both leaves and roots. GO and KEGG analysis showed that carbohydrate metabolism, polyamine and amino acid metabolism and the plant hormone signaling pathway were enriched in the leaves and roots of ‘Qinghai’ after osmotic stress. The genes involving in carbohydrate metabolism were up-regulated, and sucrose, trehalose and raffinose levels were consistently increased. The genes involved in polyamine and amino acid metabolism were up-regulated in leaves in response to osmotic stress and several amino acids, such as Glu, Met and Val levels were increased, while the genes involved in photosynthesis, carbon fixation and citrate cycle in leaves were down-regulated. In addition, the genes involved in plant hormone biosynthesis and signal transduction were altered in leaves after osmotic stress. This study provided promising candidate genes for studying drought mechanisms in ‘Qinghai’ and improving the drought tolerance of Kentucky bluegrass and drought-sensitive crops.

Kentucky bluegrass (Poa pratensis L . ) is an excellent cool-season turfgrass utilized widely in Northern China. However, turf quality of Kentucky bluegrass declines significantly due to drought. Ethephon seeds-soaking treatment has been proved to effectively improve the drought tolerance of Kentucky bluegrass seedlings. In order to investigate the effect of ethephon leaf-spraying method on drought tolerance of Kentucky bluegrass and understand the underlying mechanism, Kentucky bluegrass plants sprayed with and without ethephon are subjected to either drought or well watered treatments. The relative water content and malondialdehyde conent were measured. Meanwhile, samples were sequenced through Illumina. Results showed that ethephon could improve the drought tolerance of Kentucky bluegrass by elevating relative water content and decreasing malondialdehyde content under drought. Transcriptome analysis showed that 58.43% transcripts (254,331 out of 435,250) were detected as unigenes. A total of 9.69% (24,643 out of 254,331) unigenes were identified as differentially expressed genes in one or more of the pairwise comparisons. Differentially expressed genes due to drought stress with or without ethephon pre-treatment showed that ethephon application affected genes associated with plant hormone, signal transduction pathway and plant defense, protein degradation and stabilization, transportation and osmosis, antioxidant system and the glyoxalase pathway, cell wall and cuticular wax, fatty acid unsaturation and photosynthesis. This study provides a theoretical basis for revealing the mechanism for how ethephon regulates drought response and improves drought tolerance of Kentucky bluegrass.

Rapid rise in temperature in summer causes severe injury to cool-season turfgrass of both native species and introduced ones in Heilongjiang of Northeast China. The objectives of this study were to compare physiological responses to seasonal heat stresses and turf performances between native and introduced commercial Poa accessions. Three Chinese native Poa species ( i.e., P. pratensis, P. sibirica and P. sphondylodes ) and three USA Kentucky bluegrass cultivars (ie. ‘ Midnight’, ‘Moonlight’ and ‘BlueChip’) were evaluated under field conditions in 2017 and 2018. All accessions showed unique characteristics and considerable seasonal differences in response to temperatures. However, performances over all accessions were largely similar in early spring and autumn. In summer, native P. pratensis performed similar to ‘Midnight’, ‘Moonlight’ or ‘BlueChip’, with respect to such traits or parameters as quality, coverage, color intensity, growth rate, osmolytes, ROS and anti-oxidant production. Native P. pratensis could be used as a new turf resource for further improvement and application under the specific climatic conditions in Heilongjiang; native P. sphondylodes may be used in repairing damaged environments or for alternative seasonal greenness.