Ryegrass Plants Research Articles

Epichloë endophytes can alleviate water deficit effects on perennial ryegrass through host morpho-physiological modulation

Water deficit stress largely limits plant growth and survival in natural and managed ecosystems. We studied the morpho-physiological responses of plants associated with distinct strains of Epichloë fungal endophytes to water deficit. We hypothesised that Epichloë symbionts would alleviate the negative effects of water deficit on plants and that both magnitude and mechanisms of endophyte-based alleviation would vary depending on the Epichloë strain. Perennial ryegrass (Lolium perenne) plants from the experimental cultivar GA66 associated with the Epichloë strains AR1, AR5, AR6, and AR37 were subjected to a treatment of sustained water deficit in a pot experiment under controlled growth conditions. We measured plant biomass (shoot and root), water retention, stress-related phytohormones (abscisic acid, jasmonic acid), proline and other water-soluble amino acids, and Epichloë-derived antiherbivore alkaloids. Alleviation of the negative effects of water deficit on plants depended on the Epichloë strain, with AR37 and AR5 providing the greatest protection followed by AR1, while AR6 did not alleviate stress. The AR37-derived water deficit alleviation was associated with enhanced root biomass and plant water retention, and increased concentrations of abscisic acid, proline, and fungal alkaloids. The AR5-derived stress alleviation was associated with enhanced plant water retention and increased proline concentrations, and the AR1-derived alleviation with increased fungal alkaloid concentrations and mycelial biomass. Although AR6 did not alleviate the water deficit, the stress increased Epichloë-derived alkaloid concentrations (and enhanced root biomass) which could provide an advantage for resisting herbivory. Our study highlighted that while Epichloë generally alleviated the effects of water deficit on plants, the mechanisms of stress alleviation varied among associations, and that the host fitness could be increased even in those associations where endophytes did not alleviate direct water deficit stress if herbivores would be present.

Identification, Pathogenicity, and Fungicide Sensitivity of Colletotrichum Species Associated with Anthracnose on Italian Ryegrass in Southwestern China.

Italian ryegrass (Lolium multiflorum L.) is widely cultivated as an important forage worldwide because of its high nutritional value and good palatability. Anthracnose caused by Colletotrichum species was a common and new emerging disease of Italian ryegrass. In this study, 88 Colletotrichum isolates were collected from diseased leaves of Italian ryegrass planting regions in Sichuan, Chongqing and Guizhou provinces of southwestern China between 2019 and 2022. By pure culture technique, 15 representative single-spore isolates were obtained for further study. Multi-locus phylogenetic analysis coupled with morphological features showed that these isolates were finally identified as six new record species: C. cereale of the C. graminicola species complex, C. fioriniae and C. nymphaeae of the C. acutatum species complex, C. boninense and C. citricola of the C. boninense species complex, and C. nageiae. Pathogenicity tests indicated that all species could induce anthracnose symptoms; of these, C. cereale was more invasive than other species, followed by C. fioriniae, C. nageiae, C. citricola and C. boninense; C. nymphaeae was weakest pathogenic to Italian ryegrass plants (P ≤ 0.05). Fungicide sensitivity assays showed that iprodione, propineb and oxime·tebuconazole had strong inhibitory effect on the mycelial growth of six Colletotrichum species; in addition, azoxystrobin and fludioxonil also significantly inhibited the mycelial growth of C. nymphaeae and C. fioriniae, respectively. These results provide the basis for the diagnosis and detection in the field, pathogen identification and management of anthracnose on Italian ryegrass.

Combined use of chemical dust suppressant and herbaceous plants for tailings dust control.

Tailings dust can negatively affect the surrounding environment and communities because the tailings are vulnerable to wind erosion. In this study, the effects of halides (sodium chloride [NaCl], calcium chloride [CaCl2], and magnesium chloride hexahydrate [MgCl2·6H2O]), and polymer materials (polyacrylamide [PAM], polyvinyl alcohol [PVA], and calcium lignosulfonate [LS]) were investigated for the stabilization of tailings for dust control. Erect milkvetch (Astragalus adsurgens), ryegrass (Lolium perenne L.), and Bermuda grass (Cynodon dactylon) were planted in the tailings and sprayed with chemical dust suppressants. The growth status of the plants and their effects on the mechanical properties of tailings were also studied. The results show that the weight loss of tailings was stabilized by halides and polymers, and decreased with increasing concentration and spraying amount of the solutions. The penetration resistance of tailings stabilized by halides and polymers increased with increasing concentration and spraying amount of the solutions. Among the halides and polymers tested, the use of CaCl2 and PAM resulted in the best control of tailings dust, respectively. CaCl2 solution reduces the adaptability of plants and therefore makes it difficult for grass seeds to germinate normally. PAM solutions are beneficial for the development of herbaceous plants. Among the three herbaceous species, ryegrass exhibited the best degree of development and was more suitable for growth in the tailings. The ryegrass plants planted in the tailings sprayed with PAM grew the best, and the root-soil complex that formed increased the shear strength of the tailings.

Traditional compost and BSF-biodigested compost in the organic fertilization of ryegrass

The present study is a contribution to evaluate the agronomic potential of two different organic products (cattle effluents, either composted or digested by Black Soldier Fly larvae) as organic fertilizers, through the measurement of production and the photosynthetic activity of ryegrass (Lolium multiflorum L.), growing in a sandy soil, treated with different doses of those products. Within this aim, an experiment was conducted in a semi-controlled greenhouse with ryegrass plants cultivated in pots, with ten treatments: four different treatments of traditionally composted material, four different treatments of biodigested material, a mineral control (using the recommended rate of mineral fertilizer for ryegrass), and a zero control (without any type of fertilization). Under the experimental conditions, the results showed a significant effect of both organic composts over mineral fertilization, with a better performance of the biodigested by black soldier fly larvae. As for the informative capacity of photosynthetic activity data, in assessing the vegetative development of crops, "net assimilation rate" and "water use efficiency" proved to be the most suitable parameters.

MicroRNA164 Affects Plant Responses to UV Radiation in Perennial Ryegrass.

Increasing the ultraviolet radiation (UV) level, particularly UV-B due to damage to the stratospheric ozone layer by human activities, has huge negative effects on plant and animal metabolism. As a widely grown cool-season forage grass and turfgrass in the world, perennial ryegrass (Lolium perenne) is UV-B-sensitive. To study the effects of miR164, a highly conserved microRNA in plants, on perennial ryegrass under UV stress, both OsmiR164a overexpression (OE164) and target mimicry (MIM164) transgenic perennial ryegrass plants were generated using agrobacterium-mediated transformation, and UV-B treatment (~600 μw cm-2) of 7 days was imposed. Morphological and physiological analysis showed that the miR164 gene affected perennial ryegrass UV tolerance negatively, demonstrated by the more scorching leaves, higher leaf electrolyte leakage, and lower relative water content in OE164 than the WT and MIM164 plants after UV stress. The increased UV sensitivity could be partially due to the reduction in antioxidative capacity and the accumulation of anthocyanins. This study indicated the potential of targeting miR164 and/or its targeted genes for the genetic manipulation of UV responses in forage grasses/turfgrasses; further research to reveal the molecular mechanism underlying how miR164 affects plant UV responses is needed.

Dissecting the Roles of Phosphorus Use Efficiency, Organic Acid Anions, and Aluminum-Responsive Genes under Aluminum Toxicity and Phosphorus Deficiency in Ryegrass Plants.

Aluminum (Al) toxicity and phosphorus (P) deficiency are widely recognized as major constraints to agricultural productivity in acidic soils. Under this scenario, the development of ryegrass plants with enhanced P use efficiency and Al resistance is a promising approach by which to maintain pasture production. In this study, we assessed the contribution of growth traits, P efficiency, organic acid anion (OA) exudation, and the expression of Al-responsive genes in improving tolerance to concurrent low-P and Al stress in ryegrass (Lolium perenne L.). Ryegrass plants were hydroponically grown under optimal (0.1 mM) or low-P (0.01 mM) conditions for 21 days, and further supplied with Al (0 and 0.2 mM) for 3 h, 24 h and 7 days. Accordingly, higher Al accumulation in the roots and lower Al translocation to the shoots were found in ryegrass exposed to both stresses. Aluminum toxicity and P limitation did not change the OA exudation pattern exhibited by roots. However, an improvement in the root growth traits and P accumulation was found, suggesting an enhancement in Al tolerance and P efficiency under combined Al and low-P stress. Al-responsive genes were highly upregulated by Al stress and P limitation, and also closely related to P utilization efficiency. Overall, our results provide evidence of the specific strategies used by ryegrass to co-adapt to multiple stresses in acid soils.

Transcriptome-Based Weighted Gene Co-Expression Network Analysis Reveals the Photosynthesis Pathway and Hub Genes Involved in Promoting Tiller Growth under Repeated Drought–Rewatering Cycles in Perennial Ryegrass

Drought stress, which often occurs repeatedly across the world, can cause multiple and long-term effects on plant growth. However, the repeated drought–rewatering effects on plant growth remain uncertain. This study was conducted to determine the effects of drought–rewatering cycles on aboveground growth and explore the underlying mechanisms. Perennial ryegrass plants were subjected to three watering regimes: well-watered control (W), two cycles of drought–rewatering (D2R), and one cycle of drought–rewatering (D1R). The results indicated that the D2R treatment increased the tiller number by 40.9% and accumulated 28.3% more aboveground biomass compared with W; whereas the D1R treatment reduced the tiller number by 23.9% and biomass by 42.2% compared to the W treatment. A time-course transcriptome analysis was performed using crown tissues obtained from plants under D2R and W treatments at 14, 17, 30, and 33 days (d). A total number of 2272 differentially expressed genes (DEGs) were identified. In addition, an in-depth weighted gene co-expression network analysis (WGCNA) was carried out to investigate the relationship between RNA-seq data and tiller number. The results indicated that DEGs were enriched in photosynthesis-related pathways and were further supported by chlorophyll content measurements. Moreover, tiller-development-related hub genes were identified in the D2R treatment, including F-box/LRR-repeat MAX2 homolog (D3), homeobox-leucine zipper protein HOX12-like (HOX12), and putative laccase-17 (LAC17). The consistency of RNA-seq and qRT-PCR data were validated by high Pearson’s correlation coefficients ranging from 0.899 to 0.998. This study can provide a new irrigation management strategy that might increase plant biomass with less water consumption. In addition, candidate photosynthesis and hub genes in regulating tiller growth may provide new insights for drought-resistant breeding.

Influence of conditioner and straw on the herbaceous plant-based phytoremediation copper tailings: a field trial at Liujiagou tailings pond, China.

A field trial was performed to carry out an enhanced phytoremediation technique for multi-metal contaminated copper tailings by Sudan grass (Sorghum Sudanese), ryegrass (Lolium perenne L.), and Bermuda grass (Cynodon dactylon), using conditioner (TH-LZ01) and straw combination into composite amendments as soil amendments, aimed to obtain the maximum of phytoremediation effect. The results showed that compared with untreated herbaceous plants, the application of conditioner and straw planted with herbaceous plants reduced the pH and conductivity and increased the organic matter and water content of the copper tailings to different degrees. With the addition of conditioner and straw, the DTPA-Cd, DTPA-Cu, DTPA-Pb, and DTPA-Zn contents in the copper tailings showed a decreasing trend compared with the untreated group. The herbaceous plants were promoted to reduce the percentage contents of acid soluble fractions Cd, Cu, Pb, and Zn and to increase the percentage contents of reducible, oxidizable, and residual fractions heavy metals (Cd, Cu, Pb, and Zn) in the copper tailings to different degrees. The contents of Cd, Cu, Pb, and Zn in the underground part of herbaceous plants were higher than those in the aboveground part, and the contents of Cd, Cu, Pb, and Zn in the aboveground part and underground part decreased after adding conditioner and straw, which indicated that the conditioner and straw inhibited the transport of heavy metals in the plant. Furthermore, the principal component analysis showed that the application of conditioner and straw with planting ryegrass had more potential for improving the physicochemical properties of copper tailings and reducing heavy metal toxicity, followed by Bermuda grass and Sudan grass.

Biochars assisted phytoremediation of polycyclic aromatic hydrocarbons contaminated agricultural soil: Dynamic responses of functional genes and microbial community

A biochar-intensified phytoremediation experiment was designed to investigate the dynamic effects of different biochars on polycyclic aromatic hydrocarbon (PAH) removal in ryegrass rhizosphere contaminated soil. Maize and wheat straw biochar pyrolyzed at 300 °C and 500 °C were amended into PAH-contaminated soil, and then ryegrass (Lolium multiflorum L.) was planted for 90 days. Spearman's correlations among PAH removal, enzyme activity, abundance of PAH-ring hydroxylating dioxygenase (PAH-RHDα), and fungal and bacterial community structure were analyzed to elucidate the microbial degradation mechanisms during the combined remediation process. The results showed that 500 °C wheat straw biochar had higher surface area and more nutrients, and significantly accelerated the phytoremediation of PAHs (62.5 %), especially for high molecular weight PAH in contaminated soil. The activities of urease and dehydrogenase and the abundance of total and PAH-degrading bacteria, which improved with time by biochar and ryegrass, had a positive correlation with the removal rate of PAHs. Biochar enhanced the abundance of gram-negative (GN) PAH-RHDα genes. The GN PAH-degraders, Sphingomonas, bacteriap25, Haliangium, and Dongia may play vital roles in PAH degradation in biochar-amended rhizosphere soils. Principal coordinate analysis indicated that biochar led to significant differences in fungal community structures before 30 days, while the diversity of the bacterial community composition depended on planting ryegrass after 60 days. These findings imply that the structural reshaping of microbial communities results from incubation time and the selection of biochar and ryegrass in PAH-contaminated soils. Applying 500 °C wheat straw biochar could enhance the rhizoremediation of PAH-contaminated soil and benefit the soil microbial ecology.

Chemical Ecology of Rathayibacter toxicus and Associated Bacteria: Profiling Volatile Compounds for Insights into Annual Ryegrass Toxicity Causative Agent

The study involved the isolation of bacteria from the surface of Rathayibacter toxicus infested ryegrass seeds, followed by an analysis of volatile organic compounds (VOCs) to identify biomarkers associated with each bacterial species. Among the four isolated bacteria (a species of Pantoea, two species of Pseudomonas and R. toxicus), three were evaluated for their antibiosis potential against R. toxicus. The main objective of this research was to characterize the volatile compounds produced by R. toxicus and to assess the capability of the other three bacteria to serve as biological control agents. The volatile chemicals were identified by using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC–MS) in the aforementioned bacterial species. The identified compounds such as 1-nonanol, geraniol, decanoic acid and 2-decanone may serve as biomarkers for R. toxicus. Additionally, obtained information on VOCs may facilitate chemical communication between bacteria and the nematode which is responsible to carry it to the ryegrass plant. During the antibiosis assay, Pantoea agglomerans and Pseudomonas cedrina, among the endophytic/epiphytic bacterial species, produced compounds that significantly inhibited R. toxicus growth in vitro, with capacity values 22.7 ± 2.3 and 20.0 ± 2.0, respectively. In conclusion, this study's findings have significant implications for the management of annual ryegrass toxicity (ARGT), as they highlight the promising potential of P. agglomerans and Ps. cedrina as viable candidates for biological control strategies in ARGT management.

Evaluation of 16S rRNA gene primer pairs for bacterial community profiling in an across soil and ryegrass plant study

AbstractIntroductionAs microbes play important roles in many hosts and niches, linking microbiota across niches is becoming an important area of research. Studying microbiota across multiple niches would allow understanding of ecosystem‐level interactions and potential points of better manipulation for agriculture gains. However, a suitable methodology to characterize microbiota from vast different niches is currently lacking. We used the plant shoot and soil as two important niches for this case study.Materials and MethodsConsidering the important linkage plant play in connecting above‐ and below‐ground ecosystems and challenges of working with plant microbiota, we first compared three commonly used 16S ribosomal RNA gene primer pairs targeting V3–V4 or V5–V7 regions coupled with Illumina sequencing for bacterial communities associated with ryegrass shoot. Then the selected primer was used to amplify bacterial communities in soil and rhizosphere samples for comparison with the commonly used 338F/806R. Finally, core operational taxonomic units (OTUs) across soil and plant niches were identified.ResultsPrimer pair 799F/1193R amplified the lowest number of plant organelle sequences (<0.2% of total sequences) and consistently showed the highest α‐diversity compared with 338F/806R and 335F/769R. For soil and rhizosphere samples, 799F/1193R also demonstrated significantly higher α‐diversity indices compared with 338F/806R. The bacterial phyla commonly detected by both primer pairs comprised >97% of the total relative abundance in soil and rhizosphere samples. In addition, the differences in bacterial communities of the soil and rhizosphere samples were more evident when using 799F/1193R than 338F/806R. Using the 799F/1193R data set, 50 core bacterial OTUs were identified across soil, rhizosphere and shoot niches, whereas only 38 core OTUs were identified when using 338F/806R. Most of these core OTUs were dominant in either shoot or soil niche.ConclusionPrimer pair 799F/1193R is suitable for bacterial community studies targeting ryegrass plant and soil microbiota, in particular for cross‐niches studies.

The Effects of Accompanying Ryegrass on Bayberry Trees by Change of Soil Property, Rhizosphere Microbial Community Structure, and Metabolites.

As a subtropical and tropical tree, bayberry (Myrica rubra) is an important fruit tree grown commercially in southern China. Interestingly, our studies found that the fruit quality of bayberry with accompanying ryegrass was significantly improved, but its mechanism remains unclear. The aim of this study was to explore the mechanism of accompanying ryegrass on the beneficial effect of the fruit quality of bayberry by measuring the vegetative growth parameters, fruit parameters with economic impact, physical and chemical properties of rhizosphere soil, microbial community structure, and metabolites of the bayberry with/without ryegrass. Notably, the results revealed a significant difference between bayberry trees with and without accompanying ryegrass in fruit quality parameters, soil physical and chemical properties, microbial community structure, and metabolites. Compared with the control without accompanying ryegrass, the planting of ryegrass increased the titratable sugar, vitamin C, and titratable flavonoid contents of bayberry fruits by 2.26%, 28.45%, and 25.00%, respectively, and decreased the titratable acid contents by 9.04%. Furthermore, based on 16S and ITS amplicon sequencing of soil microflora, the accompanying ryegrass caused a 12.47% increment in Acidobacteriota while a 30.04% reduction in Actinobacteria was recorded, respectively, when compared with the bayberry trees without ryegrass. Redundancy discriminant analysis of microbial communities and soil properties indicated that the main variables of the bacterial community included available nitrogen, available phosphorus, exchangeable aluminum, and available kalium, while the main variables of the fungal community included exchangeable aluminum, available phosphorus, available kalium, and pH. In addition, the change in microbial community structure was justified by the high correlation analysis between microorganisms and secondary metabolites. Indeed, GC-MS metabolomics analysis showed that planting ryegrass caused a 3.83%-144.36% increase in 19 metabolites such as 1,3-Dipentyl-heptabarbital and carbonic acid 1, respectively, and a 23.78%-51.79% reduction of 5 metabolites compared to the bayberry trees without the accompanying ryegrass. Overall, the results revealed the significant change caused by the planting of ryegrass in the physical and chemical properties, microbiota, and secondary metabolites of the bayberry rhizosphere soils, which provides a new insight for the ecological improvement of bayberry.

First Report of Pseudopithomyces palmicola Causing Leaf Spot on Italian Ryegrass in China.

Italian ryegrass (Lolium multiflorum) is widely cultivated for the production of forage, hay and silage worldwide, due to its high nutritional value and palatability (Feng et al. 2021). It has been infected by a number of foliar fungal diseases caused by different fungal pathogens (Xue et al. 2017, 2020; Victoria Arellano et al. 2021; Liu et al. 2023). In August 2021, three Pseudopithomyces isolates with similar colony characteristics were isolated from fresh samples of leaf spots on Italian ryegrass that was collected from the Forage Germplasm Nursery, Maming town of Qujing city, Yunnan province, China (25.53833°N, 103.60278°E). For specific isolation, tissue pieces (about 0.5 cm × 1 cm) from symptomatic leaves were surface-disinfested in 75% ethanol solution for 40s, rinsed three times in sterilized distilled water and air dried, plated on potato dextrose agar (PDA), and incubated at 25°C for 3 to 7 days in the dark. Following initial isolation, a representative isolate, KM42, was selected for further study. Colonies growing on PDA were cottony, white to grey, 53.8 to 56.9 mm diameter after 6 days in the dark at 25°C, with white and regular edge; in reverse, colonies were brown to dark brown in the center, and pale yellow toward the periphery with concentric rings. Under near-UV light at room temperature (20 ± 3°C), colonies were incubated on PDA for ten days to produce conidia. Conidia were globose or ellipsoid to amygdaloid, 1- to 3-transversely septate, 0- to 2-vertical septate, light brown to brown, measuring 11.6 to 24.4 × 7.7 to 16.8 µm (avg. 17.3 × 10.9 µm). The internal transcribed spacer regions 1 and 2 and 5.8S nuclear ribosomal RNA(ITS), large subunit nrRNA (LSU), and partial DNA-directed RNA polymerase II second largest subunit (RPB2) genes were amplified with primers described by Chen et al. (2017). Sequences were deposited in GenBank (OQ875842 for ITS, OQ875844 for LSU, and OQ883943 for RPB2). BLAST analysis of all these three segments showed 100% (ITS: MF804527), 100% (LSU: KU554630), and 99.4% (RPB2: MH249030) identity with sequences of reported isolate CBS 143931 (= UC22) of Pseudopithomyces palmicola (Lorenzini et al. 2016; Liu et al. 2018). To fulfill Koch's postulates, four 12-week-old healthy Italian ryegrass plants were spray-inoculated separately with a mycelial suspension of about 5.4 × 102 CFU/ml of an isolate of P. palmicola. In addition, four control plants were sprayed with sterilized distilled water. All plants were individually covered with transparent polyethylene bags for 5 days to maintain high relative humidity and placed in a greenhouse at 18 to 22°C. Small brown to dark brown spots developed on leaves 10 days after inoculation; symptoms were not observed on control plants. Pathogenicity tests were conducted three times by the same method. The same fungus was re-isolated from the lesions, and confirmed by morphological and molecular methods as described above. To the best of our knowledge, this is the first report of P. palmicola causing leaf spot on Italian ryegrass in China or worldwide. This information will be useful to forage grass managers and plant pathologists in recognizing the disease and developing effective control measures.

Extrachromosomal DNA-mediated glyphosate resistance in Italian ryegrass.

An Italian ryegrass population from Arkansas, USA developed glyphosate resistance due to 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene amplification. The plants in this population with approximately 70 EPSPS copies were used in the present study for the physical mapping of amplified copies of EPSPS gene to determine the possible mechanism of EPSPS gene amplification conferring glyphosate resistance in Italian ryegrass. Fluorescence in situ hybridization (FISH) analysis of glyphosate resistant (GR) Italian ryegrass plants with approximately 70 EPSPS copies displayed EPSPS hybridization signals randomly on most of the metaphase chromosomes. Glyphosate susceptible (GS) Italian ryegrass plants with one EPSPS copy displayed single prominent EPSPS hybridization signal, which was co-localized with 5S rDNA locus along with few additional signals on the outside of chromosomes. Pulsed-field gel electrophoresis (PFGE) followed by DNA blot using EPSPS gene as a probe identified a prominent EPSPS hybridization around the 400 kb region in GR DNA samples, but not in GS DNA samples. We report the extrachromosomal DNA-mediated glyphosate resistance in Italian ryegrass. Physical mapping of amplified copies of EPSPS gene in Italian ryegrass by FISH gives us a clue that the amplified copies of EPSPS gene may be present in the extrachromosomal DNA elements. Further analysis by PFGE followed by DNA blotting revealed that the extrachromosomal DNA containing EPSPS is approximately 400 kb similar in size with that of eccDNA replicon in Amaranthus palmeri. © 2023 Society of Chemical Industry.

Root aphid (Aploneura lentisci) population size on perennial ryegrass is determined by drought and endophyte strain

Climate change is anticipated to lead to an increase in the occurrence and intensity of drought and fluctuations in insect cycles that will challenge modern pasture systems. Feeding by root aphids such as Aploneura lentisci Pass. can be a significant challenge to pastures. These below-ground living aphids are commonly found in New Zealand and Australia, feeding year-round on the roots of graminaceous plants such as perennial ryegrass (Lolium perenne L.). Some strains of the fungal endophyte Epichloë festucae var. lolii in perennial ryegrass can provide protection against root aphids and greater resilience under drought, contributing to higher persistency and growth than endophyte-free plants. However, the interaction between insect pressure and drought is not understood. This study examined the effect of drought on root aphid populations and plant performance in perennial ryegrass plants relative to endophyte status (±) and endophyte strain (AR37, NZCT) in a glasshouse experiment. Plants were cloned across the drought and well-watered treatments, and half of the plants were inoculated with root aphids, whilst half of the plants were treated with insecticide. Endophyte infection with strain NZCT and AR37 reduced root aphid numbers. Aphid populations were significantly higher in drought-stressed than in well-watered plants in both endophyte-infected and endophyte-free treatments. Under drought conditions, root aphid populations were increased 4-fold in NZCT and 8-fold in AR37 and endophyte-free plants in comparison with their well-watered counterparts. Root aphids reduced shoot dry weight by 16% in drought-exposed and 26% in well-watered plants in comparison with their insecticide-treated counterparts whilst reducing root biomass by 49%. Our results suggest that root aphids are likely able to exploit the higher availability of amino acids in the plant sap of drought-exposed plants. This study provides evidence that climate change-mediated impacts of root aphids could reduce production in perennial ryegrass-dominant pastures. However, field trials would be necessary to determine whether this effect is seen in situ, where numerous additional factors will be operating at the same time.

First Report of Didymella sinensis Causing Leaf Blight on Italian Ryegrass in China.

Italian ryegrass (Lolium multiflorum Lam.) is a high-yield, high-quality forage grass and is cultivated widely in southern China. In April 2021, small black spots were observed on leaves of Italian ryegrass in the field of about 300 ha located in DuShan county, Guizhou province, China (25.62056°N, 107.53139°E). Approximately 1 to 3% of plants were affected. For isolation, eleven tissue pieces (about 0.5 × 1 cm) from four symptomatic leaves were surface-disinfested in 75% ethanol solution for 40s, rinsed thrice in sterilized distilled water and air dried; then these tissues were plated on potato dextrose agar (PDA), and incubated at 25°C for 4 days in the dark. Nine fungal isolates with similar colony characteristics were obtained, and three representative isolates (LMDS1, LMDS2 and LMDS3) were selected for further study. Colonies on PDA were 47 to 57 mm diam after 5 days, margin regular, dark gray in the center surrounded by white to gray, with floccose aerial mycelia on the upper side, and dark brown to black on the reverse side. There was no fungal sporulation when these isolates were incubated under continuous ultraviolet light on PDA, oatmeal agar (OA), malt extract agar (MEA) and potato carrot agar (PCA). ITS-rDNA, LSU-rDNA, and two other protein-coding genes (RPB2 and TUB2) were amplified with primers described by Chen et al. (2017). Sequences were deposited in GenBank (ON692740 to ON692742 for ITS, ON692775 to ON692777 for LSU, ON704660 to ON704662 for RPB2, and ON704657 to ON704659 for TUB2). BLAST analysis of all these four segments showed >99.7% identity with those sequences of ex-type isolate CGMCC 3.18348 of D. sinensis (Chen et al. 2017; Hou et al. 2020). Maximum likelihood (RAxML) phylogenetic tree based on the combined ITS, LSU, RPB2 and TUB2 alignments also showed these three isolates and the other two reported D. sinensis isolates formed a subclade with 100% bootstrap support. Referring to our previous method (Xue et al. 2020), five 8-week-old healthy plants of Italian ryegrass were spray-inoculated separately with a mycelial suspension of about 1.5 × 104 CFU/ml. In addition, five plants considered as non-inoculated controls were sprayed with sterilized distilled water. All plants were individually covered with transparent polyethylene bags for 5 days to maintain high relative humidity and placed in a greenhouse at 23 to 26°C. The small black spots similar to those observed on infected plants in the field developed on leaves fifteen days after inoculation. The symptoms consisted of brown to dark brown spots when leaves were severely infected; however, symptoms were not observed on non-inoculated plants (controls). Pathogenicity tests were carried out three times. The same fungus was re-isolated from the lesions, and confirmed by morphological characterization and molecular technique as described above, thus fulfilling Koch's postulates. To the best of our knowledge, this is the first report of D. sinensis causing leaf blight on Italian ryegrass in China. The accurate identification of this pathogen would be useful for the prevention and control of leaf spot on Italian ryegrass in the future.

The environmental risk of antibiotic resistance genes from manure compost fertilizer gradually diminished during ryegrass planting

As one of the emerging pollutants in the environment, antibiotic resistance genes (ARGs) have attracted much attention. Composting is an effective way to reduce ARGs and the compost products were often used as soil amendments. However, the environmental risk of ARGs from compost products to soil and plants has not been well studied. Here, we assessed the environmental risk of ARGs from soil and ryegrass after applying manure composting. This study detected 21 different types of ARGs. Multidrug and tetracycline resistance genes were the most dominant ones, accounting for 39.2%/12.5% and 38.6%/11.6% in soil/ryegrass, respectively. This might be attributed to the decrease of Streptomyces, which is the potential host of multidrug and tetracycline ARGs. The environmental risk value, which was associated with mobile genetic elements (MGEs) and pathogens, increased in the soil and ryegrass, and return to the original level at the end of the growth cycle. The absolute environmental risk values of AH (high additive amount of the swine manure compost) and BH (high additive amount of the sheep manure compost) decreased by 0.0826 and 0.1505, respectively. The outcomes of this study revealed the environmental behavior and risk of ARGs transferring from compost to soil, and then entering into ryegrass, which is important to assess the environmental risk of compost and provide new insights into agricultural food safety.

Different LED light intensity and quality change perennial ryegrass (Lolium perenne L.) physiological and growth responses and water and energy consumption.

Light intensity and spectral composition highly affect plant physiology, growth, and development. According to growing conditions, each species and/or cultivar has an optimum light intensity to drive photosynthesis, and different light spectra trigger photosynthetic responses and regulate plant development differently. For the maintenance of natural sports pitches, namely professional football competitions, turf quality is a key condition. Due to the architecture of most football stadiums, the lawns receive low intensities of natural light, so supplementary artificial lighting above the turf is required. The use of light-emitting diodes (LEDs) can have a higher cost-benefit ratio than traditional high-pressure sodium lamps. The continuous emission spectrum, combined with high spectral selectivity and adjustable optical power, can be used to optimize plant growth and development. Thus, perennial ryegrass (Lolium perenne L.) plants, commonly used for lawns, were primarily grown at three different intensities (200, 300, and 400 μmol m-2 s-1) of cool white light. Despite the higher water and energy consumption, 400 μmol m-2 s-1 maximizes the plant's efficiency, with higher photosynthetic rates and foliar pigment concentration, and more foliar soluble sugars and aboveground biomass accumulation. Then, it was evaluated the perennial ryegrass (Double and Capri cultivars) response to different spectral compositions [100% cool white (W), 80% Red:20% Blue (R80:B20), 90% Red:10% Blue (R90:B10), and 65% Red:15% Green:20% Blue (R65:G15:B20)] at 400 μmol m-2 s-1. Both cultivars exhibited similar responses to light treatments. In general, W contributed to the better photosynthetic performance and R90:B10 to the worst one. Water consumption and aboveground biomass were equal in all light treatments. R80:B20 allows energy savings of 24.3% in relation to the W treatment, showing a good compromise between physiological performance and energy consumption.

Co-planting improves the phytoremediation efficiency of combined phenanthrene and copper co-contaminated soils

Co-contamination from both organic and inorganic pollutants is widely distributed in soils and is more difficult to remediate compared to single-type pollution. The co-planting pattern is an ideal phytoremediation strategy to remediate contaminated soils owing to their incomparable benefits originating from plant-plant interactions, but how to choose the best plant combinations and which factors affect the final remediating efficiency are still unclear. In this study, phytoremediation with different planting strategies of three herbaceous species, namely ryegrass (Lolium perenne), Dahurian wildrye (Elymus dahuricus), and Creeping bentgrass (Agrostis stolonifera), was conducted to remediate soils contaminated with both copper (Cu) and phenanthrene (PHE). The residual PHE content of all planting patterns was significantly lower compared to the unplanted bulk soil. More than 99% of total PHE losses were related to plant-stimulated microbial degradation, and plant intake was a minor pathway for PHE removal (accounting for less than 1%). The phytoextraction was the main Cu removal process by plants and the root uptake ability of Cu was the highest in Creeping bentgrass (an average of 708.9 mg kg−1) compared to the other two plants of ryegrass (an average of 269.9 mg kg−1) and Dahurian wildrye (an average of 268.0 mg kg−1). Two species co-planting combinations (ranging from an average of 264.4–302.3 mg m−2) greatly increased the total accumulated Cu content compared to single planting patterns (ranging from an average of 163.0–263.3 mg m−2). Combing the PHE removal results, the combination of Ryegrass x Creeping bentgrass, or Creeping bentgrass x Dahurian wildrye, where one species had a high biomass and the other species had a high uptake capacity, was a successful co-planting mode for the phytoremediation of multi-contaminated soils. Furthermore, microbes e.g. Massilia affiliated to Oxalobacteraceae, Sphingomonas affiliated to Sphingomonadaceae and Burkholderiaceae that can potentially degrade PAHs, as well as Rhizobium affiliated to Rhizobiaceae, Mucilaginibacter affiliated to Sphingobacteriaceae, and Caulobacter affiliated to Caulobacteraceae that can tolerate Cu stress were enriched in the rhizosphere. Overall, our study emphasizes the plant-plant interaction and the plant-microbe association, that both regulate phytoremediation effects on co-contaminated soils.

Nitrogen Application Alleviates the Adverse Effects of Defoliation Stress on Lolium perenne L. by Enhancing the Antioxidant System and Promoting Photosynthesis

Perennial grasses undergo compensatory growth after defoliation. Nitrate is the main nitrogen source for the growth of perennial ryegrass and plays a significant role in plant resistance to stress. The aim of the study was to understand the physiological mechanism of ryegrass in response to defoliation stress under different nitrate supplies and to explore possible ways to alleviate defoliation stress. We performed pot experiments where 12-week-old ryegrass plants grown in low (0.05 mM KNO3) or moderate nitrate (5 mM KNO3) conditions were defoliated and subsequently supplied with different concentrations of nitrate following defoliation treatments. During the regrowth stage, the regrowth rate, biomass, photosynthetic parameters, and the response of the antioxidant system to low or moderate nitrate supply of ryegrass were investigated. The results showed that moderate nitrate supply after defoliation increased the content of photosynthetic pigments in ryegrass and improved its photosynthetic efficiency. In addition, adding moderate nitrate after defoliation increased the activity of antioxidant enzymes and the accumulation of osmotic regulating substances, thereby enhancing plant resistance, effectively reducing the damage to plants caused by defoliation stress, and promoting plant regrowth, especially for plants grown in a low nitrate environment before defoliation. Therefore, this study showed that the addition of exogenous nitrate could counteract some of the adverse effects of defoliation stress on the growth and development of ryegrass.