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Background Flowering is a tightly regulated process influencing yield and promoting plant genetic diversity and conservation. Orchardgrass ( Dactylis glomerata ) exhibits excellent yield traits and stress resistance, making it ideal for animal husbandry and ecological restoration. However, the molecular regulatory factors of the flowering time of orchardgrass are still unknown, limiting its molecular breeding. Results To speed up molecular breeding to enhance flowering traits in orchardgrass, we conducted a genome-wide association study (GWAS). A diverse panel of 249 orchardgrass accessions was phenotyped for heading stage and flowering time. GWAS analysis identified 359 candidate genes that overlapped or were adjacent to effective single-nucleotide polymorphisms (SNPs), which were considered potential flowering time-related genes. Furthermore, we validated that formin-like protein 18 ( DgFH18 ) and choline monooxygenase ( DgCMO-like ) was two important flowering candidate genes by overexpressing them in Arabidopsis to unravel their potential functions. Overexpression of DgFH18 and DgCMO-like positively regulated flowering time by inducing the expression of flowering-related genes. Moreover, sucrose treatment could significantly promote the expression of flavonoid pathway genes and enhance the content of total flavonoids and anthocyanins in the DgCMO-like -overexpressing lines compared to the wild type. Conclusion These results provide valuable resources for future orchardgrass breeding programs and broaden the current comprehension of flowering time regulation in perennial grasses.

Background and Aims : More intense droughts under climate change threaten species resilience. Hydraulic strategies determine drought survival in woody plants but have been hardly studied in herbaceous species. We explored the intraspecific variability of hydraulic and morphological traits as indicators of dehydration tolerance in a perennial grass, cocksfoot (Dactylis glomerata), which has a large biogeographical distribution in Europe.Methods : Twelve populations of cocksfoot originating from Mediterranean, Temperate and Northern European areas were grown in a controlled environment in pots. Dehydration tolerance, leaf and stem anatomical traits and xylem pressure associated with 88 or 50 % loss of xylem conductance (P88, P50) were measured.Key Results : Across the 12 populations of cocksfoot, P50 ranged from –3.06 to – 6.36 MPa, while P88 ranged from –5.06 to –11.6 MPa. This large intraspecific variability of embolism thresholds corresponded with the biogeographical distribution and some key traits of the populations. In particular, P88 was correlated with dehydration tolerance (r = –0.79). The dehydration-sensitive Temperate populations exhibited the highest P88 (–6.1 MPa). The most dehydration-tolerant Mediterranean populations had the greatest leaf dry matter content and leaf fracture toughness, and the lowest P88 (–10.4 MPa). The Northern populations displayed intermediate trait values, potentially attributable to frost resistance. The thickness of metaxylem vessel walls in stems was highly correlated with P50 (r = –0.92), but no trade-off with stem lignification was observed. The relevance of the linkage between hydraulic and stomatal traits is discussed for drought survival in perennial grasses.Conclusions : Compared with woody species, the large intraspecific variability in dehydration tolerance and embolism resistance within cocksfoot has consequences for its sensitivity to climate change. To better understand adaptive strategies of herbaceous species to increasing drought and frost requires further exploration of the role of hydraulic and mechanical traits using a larger inter- and intraspecific range of species.

Background Vernalization and the transition from vegetative to reproductive growth involve multiple pathways, vital for controlling floral organ formation and flowering time. However, little transcription information is available about the mechanisms behind environmental adaption and growth regulation. Here, we used high-throughput sequencing to analyze the comprehensive transcriptome of Dactylis glomerata L. during six different growth periods. Results During vernalization, 4689 differentially expressed genes (DEGs) significantly increased in abundance, while 3841 decreased. Furthermore, 12,967 DEGs were identified during booting stage and flowering stage, including 7750 up-regulated and 5219 down-regulated DEGs. Pathway analysis indicated that transcripts related to circadian rhythm, photoperiod, photosynthesis, flavonoid biosynthesis, starch, and sucrose metabolism changed significantly at different stages. Coexpression and weighted correlation network analysis (WGCNA) analysis linked different stages to transcriptional changes and provided evidence of inner relation modules associated with signal transduction, stress responses, cell division, and hormonal transport. Conclusions We found enrichment in transcription factors (TFs) related to WRKY, NAC, AP2/EREBP, AUX/IAA, MADS-BOX, ABI3/VP1, bHLH, and the CCAAT family during vernalization and floral bud development. TFs expression patterns revealed intricate temporal variations, suggesting relatively separate regulatory programs of TF modules. Further study will unlock insights into the ability of the circadian rhythm and photoperiod to regulate vernalization and flowering time in perennial grass.

This work is part of a program for the conservation and enhancement of Tunisian genetic resources of orchardgrass ( Dactylis glomerata L.). This species is of great interest, especially from an agronomic point of view. However, little information is available regarding agronomic characterization and genetic variation in Tunisian orchardgrass. This study aims to evaluate the genetic diversity of nine natural populations of orchardgrass collected in the north of Tunisia through the analysis of 16 morpho-phenological traits and 14 simple sequence repeat (SSR) markers developed from different grass species. Our results showed that the analysis of variance and multivariate analyses of quantitative parameters revealed a significant morphological and phenological variation within and among the populations mainly relating to the precocity and vigor of the plants. Moreover, the population structure was independent from the geographic origin and bioclimatic stage. At the molecular level, the 14 selected SSR markers are highly transferable and exhibited amplification in Dactylis glomerata . An average of 5.27 alleles with a polymorphism information content (PIC) of 0.69 per locus set was detected among the populations studied. The average polymorphic rate for this species was 86.08%, suggesting a high degree of genetic diversity. A high level of genetic diversity (G st = 65.49%) was observed among the populations. Bayesian clustering based on SSR data clearly segregated populations into two groups. The results of this study will be useful to identify suitable populations that could be used in breeding programs for the improvement of Tunisian orchardgrass.

Plant-growth-promoting endophytes (PGPE) are a kind of beneficial microorganisms which could inhabit plant tissues to antagonize certain plant pathogens and promote the host plant’s growth and development. At present, many studies have confirmed the mutualistic effect of endophytes with plants, but there are few systematic studies on beneficial roles between endophytes and Dactylis glomerata, especially on the PGPE characteristics of the forage and environmental restoration plant. This study aimed to isolate PGPE from D. glomerata, evaluate their effects on plant growth, and ultimately acquire desirable microbial inoculants for agricultural use. First, endophytes were isolated from D. glomerata by plant re-inoculation experiment, and identified by morphological and molecular analyses. Fixation medium and methods were carried out to assess the nitrogen fixation ability of the strains. Then, the ability to dissolve phosphorus was determined by the Olsen and silicate medium methods; secretory IAA was measured by Salkowski colorimetric method; and the inhibitive effects on phytopathogen were observed by confrontation culture. Twenty-one strains were isolated from four varieties of D. glomerata, among which 14 strains with plant-growth-promoting characteristics were obtained by re-inoculation experiments, including seven endophytic bacteria and seven endophytic fungi. Further evaluation of three selected strains with the most significant PGP attributes were performed by using the pot re-inoculation experiment which revealed that TG2-B derived from Myroides odoratimimus was the most effective plant-growth-promoting agent due to its ability to produce high levels of IAA; the strain Bacillus cereus exhibited the most robust ability in dissolving inorganic phosphorus; and Trichoderma harzianum manifested a conspicuously antagonistic effect against a variety of plant pathogens. For the first time, this study reports the identification of D. glomerata endophytes that were able to promote plant growth and have a considerable antagonistic effects on plant pathogens, which could be considered as microbial inoculants for using in improving crop production and plant disease control.

The concentrations of nitrogen dioxide (NO2) and tropospheric ozone (O3) in urban and industrial site atmospheres are considered key factors associated with pollen-related respiratory allergies. This work studies the effects of NO2 and O3 on the protein expression profile and IgE binding in patients with grass allergies to Dactylis glomerata pollen extracts. Pollens were collected during the flowering season and were exposed to NO2 and O3 in a controlled environmental chamber. The amount of soluble protein was examined using the Bradford method, and the protein expression profile and antigenic properties were analysed using the immunoblotting and enzyme-linked immunosorbent assay (ELISA), respectively. Our results showed apparent inter-sera differences concerning the number and intensity of IgE reactivity, with the most prominent at bands of 55 kDa, 35, 33, and 13 kDa. In the 13 kDa band, both gases tend to induce an increase in IgE binding, the band at 33 kDa showed a tendency towards a reduction, particularly pollen exposed to O3. Reactive bands at 55 and 35 kDa presented an increase in the IgE binding pattern for all the patient sera samples exposed to NO2, but the samples exposed to O3 showed an increase in some sera and in others a decrease. Regarding the ELISA results, out of the 21 tested samples, only 9 showed a statistically significant increase in total IgE reactivity after pollen exposure to the pollutants. Our study revealed that although airborne pollen allergens might be affected by air pollution, the possible impacts on allergy symptoms might vary depending on the type of pollutant and the patient’s sensitisation profile.

Plant volatiles mediate interactions with herbivores, herbivore enemies, and abiotic stresses, but these interactions mostly have been studied with individual isolated plants. It is not yet known how intra- and interspecific plant competition influence volatile emission. In a greenhouse experiment, we investigated the volatile emission by red clover ( Trifolium pratense ) growing alone, with a conspecific, or with an individual of the naturally co-occurring orchard grass, Dactylis glomerata . The individual and combined effects of above- and below ground plant contact were investigated. When T. pratense grew together with a conspecific, both total and herbivore-induced emission of volatiles was significantly reduced as compared to T. pratense growing with D. glomerata or growing alone. This reduction in emission occurred despite the fact that there was a significant reduction in T. pratense biomass due to competition with D. glomerata . The suppression of T. pratense volatile emission growing next to a conspecific was a general pattern observed for all major herbivore-induced volatiles and independent of whether plants were in contact above ground, below ground, or both above- and below ground. The reduction in volatile emission from plants growing with conspecifics may serve to reduce attack by specialist herbivores and minimize exploitation of herbivore attack information by neighbors.

The ability of tall fescue (Festuca arundinacea L.) and orchardgrass (Dactylis glomerata L.), to remediate leachates polluted with S-metolachlor (SMR) has been assessed in static hydroponic cultures. Different SMR concentrations (0.25, 1.00, and 2.00 mg L−1) were applied in the growth media to test the capacity of the two grasses to tolerate and uptake this herbicide, and to regrowth after mowing. S-metolachlor did not severely affect the dry weight aerial biomass of D. glomerata and F. arundinacea, which were reduced by 5% and 10%, respectively, when compared to the untreated control, regardless of the SMR concentrations in the leachate. The regrowth ability of aerial biomass after mowing was reduced at the different SMR concentrations, according to a dose–response model. The SMR concentrations, which reduced the regrowth ability of F. arundinacea and D. glomerata of 10% and 30%, were found to be EC10 (Effective Concentration) of 0.21 and 0.38 mg L−1 and EC30 of 0.45 and 0.74 mg L−1, respectively. These values could be assumed as the SMR concentrations that were well tolerated by both the species, without compromising their aerial biomass regrowth. Finally, tall fescue was found to be more effective and faster than orchardgrass in decreasing the SMR in the leachate and, therefore, this species should be preferred to be used in the vegetative buffer strips (VBS).

Zinc is essential for the growth and development of plants, but in excessive amounts in the soil it can be toxic for them. Its mobility depends in part on the organic matter content of the soil. The aim of the study was to investigate the effect of application of increasing amounts of zinc (200, 400 and 600 mg Zn·kg−1 of soil) together with various forms of organic fertilizer (cattle manure, chicken manure and spent mushroom substrate) on the yield of cocksfoot and the content and uptake of this metal, and to determine its bioaccumulation factor and tolerance indices. A minor effect of zinc on cocksfoot, expressed as a decrease in yield, was observed following the application of 400 mg Zn·kg−1 of soil. Increasing application to 600 mg Zn·kg−1 caused a significant decrease in yield. Application of 400 and 600 mg Zn·kg−1 of soil significantly reduced the value of the Zn/Org tolerance index. Increasing levels of zinc application increased its content and uptake by cocksfoot and reduced the bioaccumulation factor in the plants. All of the organic materials applied increased the yield of cocksfoot and its uptake of zinc. Spent mushroom substrate increased the Zn/Org tolerance index, while cattle manure and chicken manure increased the Org/Zn tolerance index, which confirms their protective action against high zinc content in the soil.

Main conclusion : According to the results presented in this paper the fungal endophyte Epichloee typhina significantly improves the growth, PSII photochemistry and C assimilation efficiency of its host Dactylis glomerata. In this paper, we present a comprehensive study of the impact of the endophytic fungi Epichloee typhina on its plant hosts' photosynthesis apparatus. Chlorophyll a fluorescence, gas exchange, immuno-blotting and spectrophotometric measurements were employed to assess photosynthetic performance, changes in pigment content and mechanisms associated with light harvesting, carbon assimilation and energy distribution in Dactylis glomerata colonized with Epichloee typhina. According to the results presented in this study, colonization of D. glomerata results in improved photosynthesis efficiency. Additionally, we propose a new mechanism allowing plants to cope with the withdrawal of a significant fraction of its energy resources by the endophytic fungi. The abundance of LHCI, LHCII proteins as well as chlorophyll b was significantly higher in E+ plants. Malate export out of the chloroplast was shown to be increased in colonized plants. To our knowledge, we are the first to report this phenomenon. Epichloee colonization improved PSII photochemistry and C assimilation efficiency. Elevated energy demands of E+ D. glomerata plants are met by increasing the rate of carbon assimilation and PSII photochemistry.