Half of the 18O enrichment of leaf sucrose is conserved in leaf cellulose of a C3 grass across atmospheric humidity and CO2 levels.

The 18O enrichment (Δ18O) of cellulose (Δ18OCel) is recognized as a unique archive of past climate and plant function. However, there is still uncertainty regarding the proportion of oxygen in cellulose (pex) that exchanges post-photosynthetically with medium water of cellulose synthesis. Particularly, recent research with C3 grasses demonstrated that the Δ18O of leaf sucrose (Δ18OSuc, the parent substrate for cellulose synthesis) can be much higher than predicted from daytime Δ18O of leaf water (Δ18OLW), which could alter conclusions on photosynthetic versus post-photosynthetic effects on Δ18OCel via pex. Here, we assessed pex in leaves of perennial ryegrass (Lolium perenne) grown at different atmospheric relative humidity (RH) and CO2 levels, by determinations of Δ18OCel in leaves, Δ18OLGDZW (the Δ18O of water in the leaf growth-and-differentiation zone) and both Δ18OSuc and Δ18OLW (adjusted for εbio, the biosynthetic fractionation between water and carbohydrates) as alternative proxies for the substrate for cellulose synthesis. Δ18OLGDZW was always close to irrigation water, and pex was similar (0.53 ± 0.02 SE) across environments when determinations were based on Δ18OSuc. Conversely, pex was erroneously and variably underestimated (range 0.02-0.44) when based on Δ18OLW. The photosynthetic signal fraction in Δ18OCel is much more constant than hitherto assumed, encouraging leaf physiological reconstructions.

Anti-herbivory defences delivered by Epichloë fungal endophytes: a quantitative review of alkaloid concentration variation among hosts and plant parts.

BACKGROUND AND AIMS: In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant-endophyte associations and plant parts. METHODS: We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum, Lolium perenne, Lolium pratense, Lolium multiflorum|Lolium rigidum and Festuca rubra, associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. KEY RESULTS: Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum, and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. CONCLUSIONS: Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions.

Aromatic border plants in early season berries do not increase parasitism of spotted wing drosophila, Drosophila suzukii.

BACKGROUND: The spotted wing drosophila, Drosophila suzukii Matsumura, is a South-East Asian vinegar fly that is a serious worldwide economic threat to the small fruit industry. Typical control consists of weekly pesticide applications, which can have nontarget effects, increase residual pesticides and lead to the development of resistance within pest populations. One potential alternate method of control is the planting of aromatic intercrops to attract the natural enemies of D. suzukii and/or repel the flies directly. We intercropped strawberry rows with flowering sweet alyssum or ryegrass-clover (control) to evaluate their efficacy at mitigating D. suzukii infestation through the attraction of two specialized larval parasitoids, Leptopilina japonica (Novkovic and Kimura) and Ganaspis brasiliensis (Ihering). RESULTS: Our study did not demonstrate any significant effect of sweet alyssum intercropping on the infestation rate of D. suzukii in strawberries or parasitism level. However, we found that advanced sampling date and recorded numbers of D. suzukii larvae and parasitoids were positively correlated, indicating higher populations at the end of the strawberry-growing season. CONCLUSIONS: Sweet alyssum intercrops did not reduce D. suzukii infestation rates or increase parasitism levels, likely due to low population numbers in early season berry varieties. Aromatic intercrops may be more effective for increasing pest control in later season crops. © 2022 Society of Chemical Industry.

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To explore the effects of exogenous melatonin on antioxidant capacity and nutrient uptake of plants under drought stress, we used Lolium perenne and Medicago sativa potted seedlings for foliar spraying and root application of 100 µmol·L-1 melatonin, respectively. We measured the biomass, malondialdehyde (MDA) content, relative conductivity, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities, as well as nutrient contents (organic carbon, total nitrogen, total phosphorus) under drought stress. The results showed that the biomass of L. perenne and M. sativa decreased significantly under drought stress, and that external melatonin application could effectively alleviate the inhibitory effect of drought stress on L. perenne and M. sativa. Foliar spray and root application of melatonin under drought stress enhanced L. perenne biomass by 14.5% and 29.6%, and that of M. sativa by 36.6% and 49.1%, respectively. The SOD and POD activities in L. perenne and SOD activity in M. sativa significantly decreased under drought stress, and exogenous melatonin significantly increased SOD, POD and CAT activities in L. perenne and M. sativa, reduced the accumulation of MDA in leaves, caused a significant decrease in the relative conductivity of leaves, and significantly increased antioxidant capacity. Drought stress and exogenous melatonin did not affect organic carbon content of L. perenne and M. sativa. Under drought stress, the contents of N and P in L. perenne leaves and roots and the content of N in M. sativa roots decreased, while the application of melatonin increased the contents of N and P in roots and leaves of L. perenne and M. sativa, indicating that melatonin could regulate the nutrient absorption of L. perenne and M. sativa under drought stress. In conclusion, the melatonin application not only improved the antioxidant capacity of plants, but also regulated nutrient uptake to enhance plant resilience to drought stress. Foliar spraying of melatonin was more effective than root application.

Effect of indole-3-acetic acid supplementation on the physiology of Lolium perenne L. and microbial activity in cadmium-contaminated soil.

Cadmium (Cd) pollution has led to a serious deterioration in soil quality, plant growth, and human health. Therefore, restoration of soil quality is imperative. Phytoremediation is inexpensive and yields acceptable outcomes. Phytoremediation involves interaction between plant physiology and microbial activity and has been widely used in the remediation of Cd-contaminated soil. In the present study, Lolium perenne L. (perennial ryegrass) was planted in Cd-spiked soil and indole-3-acetic acid (IAA) was used to explore the physiological and biochemical characteristics of ryegrass as well as soil enzyme activity to remove Cd. The present study provides a theoretical basis for the phytoremediation of Cd-contaminated soil. The study investigated the effect of 30-mg/kg Cd-spiked soil on ryegrass (C) and 30-mg/kg Cd-spiked soil on ryegrass treated with 10-mg/kg IAA (CI) compared with uncontaminated soil and ryegrass as the control. At the end of the experiment, the ryegrass biomass, total chlorophyll, superoxide dismutase (SOD) activity, and soil invertase activity in C group were decreased by 33.7%, 23.0%, 29.7%, and 18.3%, respectively, whereas the peroxidase (POD) activity and soil basal respiration increased by 17.1% and 87.9%, respectively, compared with the control. In the CI group, the biomass of ryegrass, chlorophyll content, SOD activity, sucrase activity, fluorescein diacetate (FDA) hydrolase activity, and Cd removal rates increased by 14.5%, 19.9%, 24.3%, 12.1%, 20.4%, and 15.1%, respectively, whereas the POD activity, soil basal respiration, and Cd residues in the soil declined by 8.0%, 15.0%, and 17.0%, respectively, compared with the C group. Therefore, exposure to exogenous IAA alleviated the Cd stress on ryegrass and soil microorganisms and improved Cd absorption by ryegrass from the contaminated soil.

Endophytic fungi and drought tolerance: ecophysiological adjustment in shoot and root of an annual mesophytic host grass.

Epichloid endophytic fungi, vertically transmitted symbionts of grasses, can increase plant tolerance to biotic and abiotic stress. Our aim was to identify ecophysiological mechanisms by which the endophyte Epichloë occultans confers drought tolerance to the annual grass Lolium multiflorum Lam. Endophyte-associated or endophyte-free plants were either well-watered or subjected to water deficit. We evaluated plant biomass, root length and nitrogen concentration, and we assessed intrinsic water use efficiency (iWUE) and its components net photosynthesis and stomatal conductance, by carbon and oxygen isotope analysis of shoot tissues. Endophyte-free plants produced more biomass than endophyte-associated ones at field capacity, while water deficit strongly reduced endophyte-free plants biomass. As a result, both types of plants produced similar biomass under water restriction. Based on oxygen isotope composition of plant cellulose, stomatal conductance decreased with water deficit in both endophyte-associated and endophyte-free plants. Meanwhile, carbon isotope composition indicated that iWUE increased with water deficit only in endophyte-associated plants. Thus, the isotope data indicated that net photosynthesis decreased more strongly in endophyte-free plants under water deficit. Additionally, endophyte presence reduced root length but increased its hydraulic conductivity. In conclusion, endophytic fungi confer drought tolerance to the host grass by adjusting shoot and root physiology.

Impacts of water deficit and post-drought irrigation on transpiration rate, root activity, and biomass yield of Festuca arundinacea during phytoextraction.

Water deficit is a hazardous threat to phytoremediation, while the photosynthetic efficiency of plant leaves can rapidly recover after post-drought irrigation, thereby enhancing the root activity, transpiration rate, and metal accumulation capacity of plants. This study was designed to test whether the phytoextraction effect of drought-stressed Festuca arundinacea could recover to normal levels after post-drought irrigation. Two drought stress levels (D1, slight stress and D2, moderate stress) were carried out at one of five plant growth stages (G1, germinating; G2, tillering; G3, jointing; G4, booting; and G5, flowering). The results showed that drought stress, regardless of level, significantly decreased the transpiration rate of F. arundinacea by 38.9%-85.7%. The degree of reduction of this physiological index was significantly higher in D1G1 and D2G1 than in other treatments. The biomass yield and root activity in D1G3, D1G4, D1G5, D2G3, and D2G4 recovered and even surpassed the normal values after rewatering, suggesting that the detrimental effects of drought stress on F. arundinacea at certain growth stages can be compensated by post-drought irrigation. Drought stress also decreased the Cd uptake capacity of F. arundinacea, and the degree of reduction depended on the stress level and growth stage. Overcompensation for Cd accumulation was observed in D1G3, D1G4, D2G3, and D2G4 after post-drought irrigation. The results indicated that suitable irrigation strategies can improve the phytoextraction effect of F. arundinacea and conserve water resources in practice.

Physiological and Gene Expression Responses of Six Annual Ryegrass Cultivars to Cobalt, Lead, and Nickel Stresses.

Heavy metals negatively affect soil quality and crop growth. In this study, we compared the tolerance of six ryegrass cultivars to cobalt (Co2+), lead (Pb2+), and nickel (Ni2+) stresses by analyzing their physiological indexes and transcript levels of genes encoding metal transporters. Compared with the other cultivars, the cultivar Lm1 showed higher germination rates and better growth under Co2+, Pb2+, or Ni2+ treatments. After 48 h of Co2+ treatment, the total antioxidant capacity of all six ryegrass cultivars was significantly increased, especially that of Lm1. In contrast, under Pb2+ stress, total antioxidant capacity of five cultivars was significantly decreased, but that of Lm1 was unaffected at 24 h. Staining with Evans blue dye showed that the roots of Lm1 were less injured than were roots of the other five ryegrass cultivars by Co2+, Pb2+, and Ni2+. Lm1 translocated and accumulated lesser Co2+, Pb2+, and Ni2+ than other cultivars. In Lm1, genes encoding heavy metal transporters were differentially expressed between the shoots and roots in response to Co2+, Pb2+, and Ni2+. The aim of these researches could help find potential resource for phytoremediation of heavy metal contamination soil. The identified genes related to resistance will be useful targets for molecular breeding.

Differences in the effects of single and mixed species of AMF on the growth and oxidative stress defense in Lolium perenne exposed to hydrocarbons.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous mutualistic plant symbionts that promote plant growth and protect them from abiotic stresses. Studies on AMF-assisted phytoremediation have shown that AMF can increase plant tolerance to the presence of hydrocarbon contaminants by improving plant nutrition status and mitigating oxidative stress. This work aimed to evaluate the impact of single and mixed-species AMF inocula (Funneliformis caledonium, Diversispora varaderana, Claroideoglomus walkeri), obtained from a contaminated environment, on the growth, oxidative stress (DNA oxidation and lipid peroxidation), and activity of antioxidative enzymes (superoxide dismutase, catalase, peroxidase) in Lolium perenne growing on a substrate contaminated with 0/0-30/120 mg phenol/polynuclear aromatic hydrocarbons (PAHs) kg-1. The assessment of AMF tolerance to the presence of contaminants was based on mycorrhizal root colonization, spore production, the level of oxidative stress, and antioxidative activity in AMF spores. In contrast to the mixed-species AMF inoculum, single AMF species significantly enhanced the growth of host plants cultured on the contaminated substrate. The effect of inoculation on the level of oxidative stress and the activity of antioxidative enzymes in plant tissues differed between the AMF species. Changes in the level of oxidative stress and the activity of antioxidative enzymes in AMF spores in response to contamination also depended on AMF species. Although the concentration of phenol and PAHs had a negative effect on the production of AMF spores, low (5/20 mg phenol/PAHs kg-1) and medium (15/60 mg phenol/PAHs kg-1) substrate contamination stimulated the mycorrhizal colonization of roots. Among the studied AMF species, F. caledonium was the most tolerant to phenol and PAHs and showed the highest potential in plant growth promotion. The results presented in this study might contribute to the development of functionally customized AMF-assisted phytoremediation strategies with indigenous AMF, more effective than commercial AMF inocula, as a result of their selection by the presence of contaminants.

Arbuscular mycorrhizal fungus facilitates ryegrass (Lolium perenne L.) growth and polychlorinated biphenyls degradation in a soil applied with nanoscale zero-valent iron.

Nanoscale zero-valent iron (nZVI) shows an excellent degradation effect on chlorinated contaminants in soil, but poses a threat to plants in combination with phytoremediation. Arbuscular mycorrhizal (AM) fungus can reduce the phyototoxicity of nZVI, but their combined impacts on polychlorinated biphenyls (PCBs) degradation and plant growth remain unclear. Here, a greenhouse pot experiment was conducted to investigate the influences of nZVI and/or Funneliformis caledonium on soil PCB degradation and ryegrass (Lolium perenne L.) antioxidative responses. The amendment of nZVI significantly reduced not only the total and homolog concentrations of PCBs in the soil, but also the ryegrass biomass as well as soil available P and root P concentrations. Moreover, nZVI significantly decreased leaf superoxide disutase (SOD) activity, while tended to decrease the protein content. In contrast, the additional inoculation of F. caledonium significantly increased leaf SOD activity and protein content, while tended to increase the catalase activity and tended to decrease the malondialdehyde content. The additional inoculation of F. caledonium also significantly increased soil alkaline phosphatase activity, and tended to increase root P concentration, but had no significantly effects on soil available P concentration, the biomass and P acquisition of ryegrass, which could be attributed to the fixation of soil available nutrients by nZVI. Additionally, F. caledonium facilitated PCB degradation in the nZVI-applied soil. Thus, AM fungus can alleviate the nZVI-induced phytotoxicity, showing great application potentials in accompany with nZVI for soil remediation.

Getting ready for the ozone battle: Vertically transmitted fungal endophytes have transgenerational positive effects in plants.

Ground-level ozone is a global air pollutant with high toxicity and represents a threat to plants and microorganisms. Although beneficial microorganisms can improve host performance, their role in connecting environmentally induced maternal plant phenotypes to progeny (transgenerational effects [TGE]) is unknown. We evaluated fungal endophyte-mediated consequences of maternal plant exposure to ozone on performance of the progeny under contrasting scenarios of the same factor (high and low) at two stages: seedling and young plant. With no variation in biomass, maternal ozone-induced oxidative damage in the progeny that was lower in endophyte-symbiotic plants. This correlated with an endophyte-mediated higher concentration of proline, a defence compound associated with stress control. Interestingly, ozone-induced TGE was not associated with reductions in plant survival. On the contrary, there was an overall positive effect on seedling survival in the presence of endophytes. The positive effect of maternal ozone increasing young plant survival was irrespective of symbiosis and only expressed under high ozone condition. Our study shows that hereditary microorganisms can modulate the capacity of plants to transgenerationally adjust progeny phenotype to atmospheric change.

NOL-mediated functional stay-green traits in perennial ryegrass (Lolium perenne L.) involving multifaceted molecular factors and metabolic pathways regulating leaf senescence.

Loss of chlorophyll (Chl) is a hallmark of leaf senescence, which may be regulated by Chl catabolic genes, including NON-YELLOW COLORING 1 (NYC1)-like (NOL). The objective of this study was to determine molecular factors and metabolic pathways underlying NOL regulation of leaf senescence in perennial grass species. LpNOL was cloned from perennial ryegrass (Lolium perenne L.) and found to be highly expressed in senescent leaves. Transient overexpression of LpNOL accelerated leaf senescence and Chl b degradation in Nicotiana benthamiana. LpNOL RNA interference (NOLi) in perennial ryegrass not only significantly blocked Chl degradation in senescent leaves, but also delayed initiation and progression of leaf senescence. This study found that NOL, in addition to functioning as a Chl b reductase, could enact the functional stay-green phenotype in perennial grass species, as manifested by increased photosynthetic activities in NOLi plants. Comparative transcriptomic analysis revealed that NOL-mediated functional stay-green in perennial ryegrass was mainly achieved through the modulation of Chl catabolism, light harvesting for photosynthesis, photorespiration, cytochrome respiration, carbohydrate catabolism, oxidative detoxification, and abscisic acid biosynthesis and signaling pathways.

Individual and combined application of Cu-tolerant Bacillus spp. enhance the Cu phytoextraction efficiency of perennial ryegrass.

Forage grasses have recently received a remarkable amount of attention as promising candidates for decontaminating metal-polluted soils, but this strategy is time-consuming and inefficient. The present study aimed to address the beneficial effects of screened plant growth-promoting rhizobacteria (PGPR) strains Bacillus sp. EhS5 and EhS7 on perennial ryegrass and tall fescue. Single or combined inoculation considerably increased the biomass yield and Cu content of inoculated ryegrass compared with uninoculated plants, thereby enhancing the extraction efficiency at different Cu contamination levels. Bioaugmentation did not show a positive impact on the improvement of fescue's phytoextraction efficiency. Principal component analysis (PCA) and Pearson correlation coefficient results identified root development and photosynthesis as the key variables influencing ryegrass biomass. Antioxidant activities and Cu bioavailability are the key variables influencing Cu accumulation. The inoculated ryegrass showed improved photosynthetic status as the photosystem II system efficiency parameters increased and energy dissipation in the form of heat (DIo/RC) decreased with the help of PGPR. The root length, diameter, surface area, and forks of inoculated ryegrass increased remarkably. The levels of scavengers of reactive oxygen species were enhanced in these plants. Moreover, PGPR significantly increased soil Cu bioavailability by secreting siderophores and organic acid and by increasing soil organic carbon content. Dual inoculation showed better results than individual inoculation in improving ryegrass growth and Cu translocation under high Cu contamination level according to PCA. This study systematically explored the effects and mechanisms of the Bacillus-ryegrass combined remediation and provided a novel method for cleaning Cu-contaminated sites.

Canonical correlations reveal adaptive loci and phenotypic responses to climate in perennial ryegrass.

Germplasm from perennial ryegrass (Lolium perenne L.) natural populations is useful for breeding because of its adaptation to a wide range of climates. Climate-adaptive genes can be detected from associations between genotype, phenotype and climate but an integrated framework for the analysis of these three sources of information is lacking. We used two approaches to identify adaptive loci in perennial ryegrass and their effect on phenotypic traits. First, we combined Genome-Environment Association (GEA) and GWAS analyses. Then, we implemented a new test based on a Canonical Correlation Analysis (CANCOR) to detect adaptive loci. Furthermore, we improved the previous perennial ryegrass gene set by de novo gene prediction and functional annotation of 39,967 genes. GEA-GWAS revealed eight outlier loci associated with both environmental variables and phenotypic traits. CANCOR retrieved 633 outlier loci associated with two climatic gradients, characterized by cold-dry winter versus mild-wet winter and long rainy season versus long summer, and pointed out traits putatively conferring adaptation at the extremes of these gradients. Our CANCOR test also revealed the presence of both polygenic and oligogenic climatic adaptations. Our gene annotation revealed that 374 of the CANCOR outlier loci were positioned within or close to a gene. Co-association networks of outlier loci revealed a potential utility of CANCOR for investigating the interaction of genes involved in polygenic adaptations. The CANCOR test provides an integrated framework to analyse adaptive genomic diversity and phenotypic responses to environmental selection pressures that could be used to facilitate the adaptation of plant species to climate change.

Natural variation of physiological traits, molecular markers, and chlorophyll catabolic genes associated with heat tolerance in perennial ryegrass accessions.

BACKGROUND: Identification of genetic diversity in heat tolerance and associated traits is of great importance for improving heat tolerance in cool-season grass species. The objectives of this study were to determine genetic variations in heat tolerance associated with phenotypic and physiological traits and to identify molecular markers associated with heat tolerance in a diverse collection of perennial ryegrass (Lolium perenne L.). RESULTS: Plants of 98 accessions were subjected to heat stress (35/30 °C, day/night) or optimal growth temperature (25/20 °C) for 24 d in growth chambers. Overall heat tolerance of those accessions was ranked by principal component analysis (PCA) based on eight phenotypic and physiological traits. Among these traits, electrolyte leakage (EL), chlorophyll content (Chl), relative water content (RWC) had high correlation coefficients (- 0.858, 0.769, and 0.764, respectively) with the PCA ranking of heat tolerance. We also found expression levels of four Chl catabolic genes (CCGs), including LpNYC1, LpNOL, LpSGR, and LpPPH, were significant higher in heat sensitive ryegrass accessions then heat tolerant ones under heat stress. Furthermore, 66 pairs of simple sequence repeat (SSR) markers were used to perform association analysis based on the PCA result. The population structure of ryegrass can be grouped into three clusters, and accessions in cluster C were relatively more heat tolerant than those in cluster A and B. SSR markers significantly associated with above-mentioned traits were identified (R2 > 0.05, p < 0.01)., including two pairs of markers located on chromosome 4 in association with Chl content and another four pairs of markers in association with EL. CONCLUSION: The result not only identified useful physiological parameters, including EL, Chl content, and RWC, and their associated SSR markers for heat-tolerance breeding of perennial ryegrass, but also highlighted the involvement of Chl catabolism in ryegrass heat tolerance. Such knowledge is of significance for heat-tolerance breeding and heat tolerance mechanisms in perennial ryegrass as well as in other cool-season grass species.

Exogenous Glutathione Alleviation of Cd Toxicity in Italian Ryegrass (Lolium multiflorum) by Modulation of the Cd Absorption, Subcellular Distribution, and Chemical Form.

Subcellular fractions and the chemical forms of cadmium (Cd) reflect its level of toxicity to plants; however, these effects of exogenous glutathione (GSH) are poorly understood. We exposed two Italian ryegrass (Lolium multiflorum) cultivars (IdyII and Harukaze) to 50 µM Cd or 200 µM GSH to investigate the effect of GSH on the Cd uptake, subcellular compartments, and chemical forms. Cd significantly inhibited the plant growth, while GSH supplementation decreased this inhibition. The application of GSH significantly improved the Cd concentration in the roots but reduced that in the shoots and decreased the Cd translocation from root to shoot. The Cd concentration of the root in the cell wall was increased while the concentration in the soluble fraction was decreased when supplied with GSH. The inorganic form (80% ethanol for Cd extraction) in the roots was significantly reduced when treated with GSH. The Cd form extracted by 2% acetic acid (HAC) with low toxicity and immobility were greatly increased. In leaves, the application GSH decreased in any form of Cd form extracted. In conclusion, exogenous GSH decreased the translocation of Cd and alleviated Italian ryegrass Cd toxicity by accumulating more Cd in the root cell wall and immobilizing more Cd in lower toxicity fractions.

Adjustment of Photosynthetic and Antioxidant Activities to Water Deficit Is Crucial in the Drought Tolerance of Lolium multiflorum/Festuca arundinacea Introgression Forms.

Lolium multiflorum/Festuca arundinacea introgression forms have been proved several times to be good models to identify key components of grass metabolism involved in the mechanisms of tolerance to water deficit. Here, for the first time, a relationship between photosynthetic and antioxidant capacities with respect to drought tolerance of these forms was analyzed in detail. Two closely related L. multiflorum/F. arundinacea introgression forms distinct in their ability to re-grow after cessation of prolonged water deficit in the field were selected and subjected to short-term drought in pots to dissect precisely mechanisms of drought tolerance in this group of plants. The studies revealed that the form with higher drought tolerance was characterized by earlier and higher accumulation of abscisic acid, more stable cellular membranes, and more balanced reactive oxygen species metabolism associated with a higher capacity of the antioxidant system under drought conditions. On the other hand, both introgression forms revealed the same levels of stomatal conductance, CO2 assimilation, and consequently, intrinsic water use efficiency under drought and recovery conditions. However, simultaneous higher adjustment of the Calvin cycle to water deficit and reduced CO2 availability, with respect to the accumulation and activity of plastid fructose-1,6-bisphosphate aldolase, were clearly visible in the form with higher drought tolerance.

Ontogenetic and trans-generational dynamics of a vertically transmitted fungal symbiont in an annual host plant in ozone-polluted settings.

Tropospheric ozone is an abiotic stress of increasing importance in the context of global climate change. This greenhouse gas is a potent phytotoxic molecule with demonstrated negative effects on crop yield and natural ecosystems. Recently, oxidative stress has been proposed as a mechanism that could regulate the interaction between cool-season grasses and Epichloë endophytes. We hypothesized that exposure of Lolium multiflorum plants, hosting endophytes to an ozone-polluted environment at different ontogenetic phases, would impact the trans-generational dynamics of the vertically transmitted fungal symbiont. Here, we found that the ozone-induced stress on the mother plants did not affect the endophyte vertical transmission but it impaired the persistence of the fungus in the seed exposed to artificial ageing. Endophyte longevity in seed was reduced by exposure of the mother plant to ozone. Although ozone exposure did not influence either the endophyte mycelial concentration or their compound defences (loline alkaloids), a positive correlation was observed between host fitness and the concentration of endophyte-derived defence compounds. This suggests that fungal defences in grass seeds were not all produced in situ but remobilized from the vegetative tissues. Our study reveals ozone trans-generational effects on the persistence of a beneficial symbiont in a host grass.

Mycelial biomass and concentration of loline alkaloids driven by complex population structure in Epichloë uncinata and meadow fescue (Schedonorus pratensis).

Many efforts have been made to select and isolate naturally occurring animal-friendly Epichloë strains for later reinfection into elite cultivars. Often this process involves large-scale screening of Epichloë-infected wild grass populations where strains are characterized and alkaloids measured. Here, we describe for the first time the use of genotyping-by-sequencing (GBS) on a collection of 217 Epichloë-infected grasses (7 S. arundinaceum, 4 L. perenne, and 206 S. pratensis). This genotyping strategy is cheaper than complete genome sequencing, is suitable for a large number of individuals, and, when applied to endophyte-infected grasses, conveniently genotypes both organisms. In total, 6273 single nucleotide polymorphisms (SNPs) in the endophyte data set and 38 323 SNPs in the host data set were obtained. Our findings reveal a composite structure with three distinct endophyte clusters unrelated to the three main S. pratensis gene pools that have most likely spread from different glacial refugia in Eurasia. All three gene pools can establish symbiosis with E. uncinata. A comparison of the endophyte clusters with microsatellite-based fingerprinting of the same samples allows a quick test to discriminate between these clusters using two simple sequence repeats (SSRs). Concentrations of loline alkaloids and mycelial biomass are correlated and differ significantly among the plant and endophyte subpopulations; one endophyte strain has higher levels of lolines than others, and one specific host genotype is particularly suitable to host E. uncinata. These findings pave the way for targeted artificial inoculations of specific host-endophyte combinations to boost loline production in the symbiota and for genome association studies with the aim of isolating genes involved in the compatibility between meadow fescue and E. uncinata.

Photosynthetic performance of five cool-season turfgrasses under UV-B exposure.

Turfgrasses are monocotyledonous plants from the family Poaceae. They are widely used in green spaces and are considered one of the most economically important horticultural crops in the world. Turfgrass quality is affected by several environmental factors including light, which is involved in the quality decline of transplanted sod. Ultraviolet-B (UV-B) is an important regulator of plant growth and development. Plants growing and/or stored in protected systems, such as in sod production, may be more vulnerable to UV-B damage than those growing in the field due to acclimation. Few studies on the effects of UV-B on turfgrass physiology have been published. Therefore, the aim of this study was to evaluate the influence of UV-B irradiation on the photosynthetic performance of five cool-season turfgrasses, namely Agrostis stolonifera L., Festuca arundinacea Schreb., Poa supina Schrad., Poa pratensis L. and Lolium perenne L. Turfgrasses were exposed to 18.25 kJ m-2 d-1 biologically effective UV-B in growth chambers under controlled conditions. Measurements included photosynthetic pigments, chlorophyll fluorescence and gas exchanges monitored for 16 d-UV-B treatment and after recovery. Content of pigments decreased with UV-B exposure with significant differences among the species. UV-B also affected the photosystem II (PSII) efficiency depending on the exposure period and species. Similarly, gas exchange parameters showed different effects among species after UV-B exposure compromising the assimilation of CO2. Multivariate analysis highlighted three main clusters of species confirming their different UV-B tolerance and ability to restore PSII photochemistry after recovery, from which Festuca arundinacea resulted to be the most tolerant.