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1.
Asexual, vertically transmitted fungal endophytes of the genus Neotyphodium are considered to enhance growth, stress resistance and competitiveness of agronomic grasses, but have been suggested to have neutral or deleterious effects on wild grasses. We studied whether the associations between Bromus auleticus and their endophytes, Neotyphodium pampeanum and Neotyphodium tembladerae, are beneficial for this wild forage grass native to South America. In a greenhouse experiment, 3‐month‐old endophyte‐infected plants (E+) showed enhanced growth relative to their endophyte‐free counterparts (E?). In a one‐year‐long experiment in the field, E+ plants showed higher survival and regrowth rate, and produced more biomass and seeds than E? plants. Only with respect to the seed output did N. tembladerae seem to be detrimental, whereas N. pampeanum did not affect this parameter. No differences were observed with respect to the germination of seeds produced by E+ or E? plants. Loline alkaloids were detected in N. pampeanum‐infected plants. Our results show that, similar to results with agronomic grasses, in wild grasses, the symbiosis with Neotyphodium species could be mutualistic.  相似文献   

2.
A symbiosis between grasses and systemic fungal endophytes exists in both natural and agricultural grassland communities. Our objective was to examine the effects of systemic endophytes on the competitive ability of two agronomically important grass species: meadow fescue [Festuca pratensis (Huds.) syn. Schedonorus pratensis (Huds.) P. Beauv] and tall fescue [Festuca arundinacea (Schreb.) syn. Schedonorus phoenix (Scop.)]. Plants of meadow and tall fescue were grown for 48 days in replacement series of interspecific mixture with a legume (red clover, Trifolium pratense L.) in different nutrient environments in a greenhouse. Neither of the grass species gained endophyte‐promoted competitive advantage over red clover in grass–clover mixtures. Endophyte infection increased the growth of meadow fescue monocultures by 89% compared to endophyte‐free monocultures in high‐nutrient soils, but plant competition or the cost of endophyte infection to the meadow fescue decreased the yield in resource‐limited conditions. On average, endophyte‐infected and endophyte‐free meadow fescues produced 0·15 and 0·17 g, and 0·14 and 0·14 g dry biomass per plant in mixtures with red clover in high‐ and low‐nutrient soils respectively. In contrast to meadow fescue, endophyte‐promoted growth of tall fescue monocultures was not detected. Endophyte‐infected and endophyte‐free tall fescue monocultures produced 0·76 and 0·95 g biomass per pot, respectively, in the high‐nutrient environment. Endophyte infection can increase the performance of the host grass, but the positive effects depend on the host species, the species composition and soil nutrient availability.  相似文献   

3.
Tall fescue (Festuca arundinacea) forms a mutualistic symbiosis with the fungal endophyte Neotyphodium coenophialum which produces ergot alkaloids toxic to grazing animals. One approach to reduce pathological effects has been to introduce an exotic endophyte that does not produce toxic compounds yet still confers host‐plant benefits. We measured biomass accumulation and competition between two tall fescue cultivars with different endophytes grown in close proximity and tested if compounds from endophytes can diffuse from one plant to another. Ky31 (tall fescue with natural endophyte) and MaxQ (tall fescue with introduced exotic endophyte) were grown separately and together in a pot experiment under greenhouse conditions. The cultivars had comparable biomass production in monoculture, but when grown in mixed‐culture MaxQ had a significantly lower tiller number (2.92 ± 0.15 tillers/plant) and size (0.048 g ± 0.003) than Ky31 (4.06 ± 0.16 tillers/plant) (0.072 ± 0.002 g). Aqueous endophyte preparations were made and applied topically to E+ and E‐ Ky31. E‐ plants receiving doses of this preparation produced significantly more tillers (3 ± 0.18 tillers/plant) and larger tillers (0.074 ± 0.006 g) than untreated control plants (2.2 ± 0.13 tillers/plant) (0.0428 ± 0.0072 g). These observations suggested that a diffusible compound might induce a growth benefit conferred by the tall fescue endophyte.  相似文献   

4.
Three Lolium perenne L. genotypes collected from different natural habitats were tested for the effects of their fungal endophyte Neotyphodium spp. on plant growth and seed yield. Half the clones of the originally infected plants were subjected to fungicide treatment to eradicate the endophytes. In an experiment, the clones were planted separately into pots and were either watered adequately or subjected to drought stress. In the genotype collected from a dry site, the endophyte infection reduced plant growth at an adequate water supply, but increased regrowth under drought. In the genotype from a periodically either flooded or dry site, endophyte infection significantly promoted the development of reproductive tillers and seed production (effects which are associated with adaptation to drought). In contrast, the genotype that originated from a wet site showed higher sensitivity to drought stress when endophyte infection was present. The results suggest that environmental conditions in the original habitat of the plants may influence the symbiotic interaction between plant and fungus, probably through natural selection. However, endophyte‐induced increases in root dry weight and root/shoot ratio were recorded for all three genotypes. These features could be beneficial for plant persistence, especially on sites where water is the growth‐limiting factor.  相似文献   

5.
This study was conducted on a mixed‐grass prairie in south‐central North Dakota, USA, to test the effect of animal grazing on rhizome biomass. Below‐ground plant biomass samples were collected from pastures with moderate and heavy grazing by beef cattle. Because the biomass data did not meet the normality assumptions, the computer resampling method involving a nested anova was used. A reduction in rhizomes was found under heavy grazing, as compared with moderate grazing. Although rhizomes only accounted for a small fraction of total below‐ground plant biomass, our study suggested that the high rhizome density found in the moderately grazed pastures might be partly responsible for the greater potential of plant regrowth in the moderately grazed pastures than in the heavily grazed pastures on this mixed‐grass prairie.  相似文献   

6.
The common forage grass Lolium perenne has evolved with the systemic fungal endophyte Epichloë festucae var. lolii. The endophyte provides herbivore resistance to the grass due to defensive alkaloids, some of which are toxic to grazing livestock. In this field study, we determine whether distribution of the endophyte‐grass association changes along a land‐use intensity gradient on 87 managed grasslands in three German regions. Endophyte infections were detected in 66% of the studied sites and infection rates within infected sites ranged from 1% to 95%. Alkaloid concentrations of lolitrem B (vertebrate toxin) exceeded the toxicity thresholds in 50 (14%) of 351 infected plants and of peramine (invertebrate deterrent/toxin) in 12 (3%) of 351 plants. Infection rates and alkaloid concentrations were not significantly affected by land‐use intensity and region, but alkaloid concentrations were higher in summer compared to spring. We conclude that risks for livestock intoxication are currently low, as (i) average alkaloid concentrations per grassland were always below toxicity thresholds and as (ii) none of the grasslands was dominated by L. perenne. We suggest avoidance of grass monocultures in Europe to keep intoxication risks for livestock low; we also recommend regular examination of seeds and grasslands, as seed producers might accidentally distribute infected seeds, and as climate warming might further enhance the distribution of Epichloë endophytes in European grasslands.  相似文献   

7.
Festuca rubra subsp. pruinosa is a grass that inhabits the sea cliffs of the Atlantic coasts of Europe. Four populations of this plant in the northern coast of Galicia, in northern Spain, were analysed for the presence of fungal endophytes. Of the plants included in the study, on average 0·69 were infected by an intercellular fungal endophyte. Using morphological and molecular characters, this endophyte was identified as Epichloë festucae, a clavicipitaceous, seed‐transmitted species. A half‐sibling line, consisting of endophyte‐free and endophyte‐infected plants, was developed and used to test whether the presence of the fungus affected the response of the plants to salinity. Dry weights of infected or uninfected plants, watered with sea‐water solutions or tap water, did not significantly differ.  相似文献   

8.
Neotyphodium endophytic fungi are beneficial for certain cultivated grass species by increasing the stress tolerance and herbivore resistance of their host plants. These grass endophytes have been widely studied in temperate regions. Endophyte-infected grasses are also cultivated in sub-artic conditions, but studies on the effects of endophyte infection on grasses under conditions of prolonged snow cover are scarce. A 2-year field experiment was conducted with two originally endophyte-infected meadow fescue ( Schedonorus pratensis ) cultivars. The growth and reproduction of endophyte-infected (E+) and endophyte-free (E−) plants of two cultivars at two sites, differing in nutrient status and duration of snow cover, were compared at the latitude of the Arctic Circle in Finland. Endophyte infection enhanced plant performance most at the site with the higher nutrient status and the shorter duration of snow cover. The difference in growth between E+ and E− grasses increased during the second growing season and was most pronounced in the reproductive investment of grasses, but the benefits of endophyte infection for reproductive mass were cultivar-dependent. At the site with the lower nutrient status, costs of endophyte infection on the vegetative growth of grasses were found. The results suggest that Neotyphodium infection may benefit meadow fescue in sub-arctic conditions but the extent of the effects is dependent on the cultivar and the environment.  相似文献   

9.
Occurrence of endophytes in grasses native to northern China   总被引：4，自引：0，他引：4  
A survey of grass species associated with Neotyphodium and Epichloë fungal endophytes was made in the permanent grasslands of northern China. A total of 41 grass species, 56 sites and 172 local populations were examined to reveal endophytic infection of native grasses. Twenty‐five of the forty‐one species of grasses (proportionately 0·61) were infected by endophytes: twenty‐two species had a mean infection rate of 0·01–0·50 and only three species had a mean infection >0·50. Of the 172 local populations examined, however, proportionately 0·72 were not infected, 0·181 had an infection rate of 0·01–0·50 and 0·099 had an infection rate of 0·51–1·00. Two genera of grasses, Cleistogenes and Koeleria, as well as twenty plant species, were previously unknown endophytic hosts in China. High infection rates (0·86–1·00) of plants of Achnatherum sibiricum were detected at all eleven sites studied. Other grasses in which high infection rates were found were Agropyron mongolicum, Roegneria turczaninovii, Agropyron elongate, Poa palustris and Poaangustifolia. It was concluded that endophytes are found widely in natural grass populations and that endophyte–grass interactions may have effects on ecosystems and livestock in the grasslands of northern China.  相似文献   

10.
The impact of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on plant population density, ground cover and soil moisture in a hill pasture (annual grass dominated, with Australian native grasses being the major perennial species) were studied in a large‐scale field experiment from 2002 to 2006 in southern Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January each year), long‐term deferred grazing (no defoliation from October to the autumn break, that is the first significant rainfall event of the winter growing season) and optimized deferred grazing (withholding time from grazing depends on morphological development of the plants). These treatments were applied with two fertilizer levels (nil fertilizer and 50 kg P ha?1 plus lime) and two additional treatments [continuous grazing (control) and no grazing for year 1]. Deferred grazing increased (P < 0·05) perennial grass tiller density compared with the control. On average, the tiller density of the three deferred grazing treatments was 27–88% higher than the control. There was a negative (P < 0·01) relationship between perennial and annual grass tiller density. Fertilizer application increased (P < 0·05) legume plant density. The densities of annual grasses, legumes, onion grass (Romulea rosea) and broadleaf weeds varied between years, but perennial grass density and moss cover did not. The ground cover of the deferred grazing treatments in autumn was on average 27% higher than the control. Soil moisture differed between treatments at 15–30 cm depth, but not at 0–15 depth over autumn and winter. The results imply that deferred grazing can be an effective tool for rejuvenating degraded native pastures through increases in native grass tiller density and population and through improving farm productivity and sustainability.  相似文献   

11.
Systemic and asymptomatic Neotyphodium fungal endophytes infect numerous species of the Poaceae. The frequencies of Neotyphodium endophyte infection in Finland were investigated among and within seven Nordic cultivars of meadow fescue, Schedonorus pratensis (Huds.) P. Beauv., which is a widely grown pasture and forage grass species in Scandinavia. The cultivars were Kasper, Salten, Antti, Fure, Ilmari, Inkeri and Kalevi. Frequencies of infection of cultivars varied from endophyte-free cultivar Fure to highly infected cultivar Inkeri [mean (standard deviation of mean) of 0·95 (0·023)]. Mean frequencies of infection of three cultivars remained lower than 0·10, and two of the cultivars, Kasper and Salten, were intermediately infected. In most of the cultivars, frequencies of infection varied only slightly among seed lots. In cultivar Kasper, however, the frequency of endophyte infection was highly variable (0–0·96) among the 45 seed lots examined. The relative importance of cultivar, seed lot and infection by Neotyphodium endophyte to the aphid Rhopalosiphum padi L. was studied experimentally, using both endophyte-free and endophyte-infected plants of four seed lots of the two intermediately infected cultivars. Endophyte infection increased plant resistance to R. padi , overriding the influences of seed lot and cultivar. It is proposed that variation caused by endophyte infections in cultivars of meadow fescue should be taken into account in assessing plant breeding programmes in Europe.  相似文献   

12.
Epichloë fungal endophytes colonize the intercellular space of aerial organs of their plant hosts without causing symptoms. These symbionts are known to improve the performance of their host grasses in some situations of biotic and abiotic stress, leading to the suggestion that they can be used to improve grass tolerance to contaminants. The grass Festuca rubra is a host of the endophyte Epichloë festucae. We used two half‐sib lines of F. rubra, each line composed of infected (E+) or endophyte‐free (E?) seeds, to study the effect of varying levels of arsenic (6, 12, 25, and 50 mg L?1), and of the endophyte in seed germination and radicle growth. The results showed that seed germination was not significantly affected by arsenic (As) levels lower than 25 mg L?1, indicating that this grass has a relatively high tolerance of As at the germination stage. The decrease in germination observed at 25 and 50 mg L?1 was due to increased seed mortality and to the reversible inhibition of the germination of viable seeds caused by As. The presence of the endophyte did not change the germination response to arsenic of one line, but affected negatively the germination of the other line. In contrast to the process of germination, radicles of E+ seeds of both lines were longer than those of endophyte‐free seeds. The results of this work indicate that Epichloë endophytes can affect the performance of some F. rubra genotypes when As is present in the soil.  相似文献   

13.
Infection with Neotyphodium endophyte was detected in 33 of 38 ecotype populations of Lolium perenne originating from old grassland at four widespread sites in Germany. The frequency of individual infected plants of the different populations ranged mostly from 1% to 30%; a few populations showed higher infection levels, up to 80%. The contribution of endophyte-positive plants to the biomass of the original swards was estimated to range from 1% to 34%.
Concentrations of the indole alkaloid lolitrem B detected in the endophyte-positive German ecotypes were similar to those in the endophyte-positive cultivars'Ellett'and'Grasslands Nui', originating in New Zealand, when all were cultivated under the climatic conditions of northern Germany. A seasonal variation in lolitrem B concentrations was observed from 1993 to 1996. The highest concentrations, 0·8–1·4 mg kg−1 dry matter of herbage, were recorded during the months of July and August. These concentrations were not considered to be sufficient to induce'ryegrass staggers', a neurological disorder in grazing animals. It is concluded that further research is necessary to elucidate the implications of grass endophytes under the climatic conditions of Central Europe.  相似文献   

14.
Abstract A survey of grass species associated with Epichloë and Neotyphodium fungal endophytes was made in permanent semi‐arid grasslands of western Spain. Endophytes were isolated from 11 of 49 grass species analysed. Infected plants of Festuca arundinacea, Festuca rubra, Dactylis glomerata and Lolium perenne were detected at most locations studied. The grasses, Agrostis castellana, Brachypodium phoenicoides and Festuca ampla, are previously unknown endophyte hosts. The results obtained show that endophyte–grass interactions are present in the grasslands where this study was conducted.  相似文献   

15.
Festuca rubra subsp. pruinosa is a grass that grows on coastal cliffs along the Atlantic coast of Europe. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae. It is not known whether the alkaloids, ergovaline and peramine, are produced by the endophyte in F. rubra subsp. pruinosa. Plants from four populations were collected from the northern coast of Galicia (Spain) and examined for the presence of fungal endophytes. Ergovaline and peramine concentrations were analysed over two consecutive years, at two plant growth stages, and in different types of plant tissues. Infected plants of F. rubra subsp. pruinosa contained ergovaline but not peramine. Ergovaline was detected in 0·80 of the plants, with concentrations ranging from 0·05 to 1·9 μg g?1 dry matter. The differences in ergovaline concentration between different types of plant tissues (vegetative and reproductive), plant populations and sampling dates were not statistically significant.  相似文献   

16.
The botanical composition, intake and digestibility of the diet consumed by 1‐year‐old weaner sheep grazing a native white grass plant community in the Falkland Islands was measured in five periods between June 1998 and March 1999. Five different sheep were used in each period. Two methods were used for estimating the botanical composition of the diet: plant cuticle patterns in the faeces of the sheep and the patterns of concentrations of n‐alkanes in the faeces of sheep. These methods were used to predict the concentrations of C32‐ and C33‐alkanes in the herbage to allow the estimation of herbage intake and digestibility using the n‐alkane technique. It was concluded that the n‐alkane technique gave more accurate estimates of diet composition based on the comparison with estimates of nutrient intake derived from liveweight gains of sheep. The dominant pasture species, Cortaderia pilosa, was the predominant species consumed during the cooler periods of the year. In the summer, when the highest liveweight gains of sheep occur, the proportion of fine grass species, including Poa spp., Festuca magellanica and Agrostis capillaris, and herbs and sedges in the diet was highest. Herbage intake was the highest during the summer periods when digestibility was also at its peak. Estimated nutritional deficiencies of metabolizable energy, crude protein, phosphorus and vitamin D3 that limit the growth and development of weaner sheep were evident for up to 9 months of the year. Targeted supplementation regimes that counter specific nutrient deficiencies could be developed on the basis of these results to address critical periods in the growth of young sheep.  相似文献   

17.
The experiment was conducted in 2005–2007 to evaluate weight performance, blood parameters associated with forage nutrient‐use and anaemia from gastrointestinal nematode (GIN) infection, and faecal egg count (FEC) patterns of meat‐goat kids finished on alfalfa (Medicago sativa L.; ALF); red clover/grass mixture (Trifolium pratense L.; RCG); and orchardgrass (Dactylis glomerata L; OGR) pastures. Forage mass, crude protein (CP) and total digestible nutrients (TDN) displayed complex interactions between treatment and time (P < 0·001) across the grazing seasons. Final body weight was greater for goats finished on ALF and RCG than on OGR, except in 2006 when ALF was greater than RCG or OGR. The TDN/CP ratios in forages and blood urea nitrogen concentrations in grazing goats were highly correlated (r = 0·99; P = 0·02) and suggested that animals were wasting forage protein. Faecal egg count was variable over the grazing season each year (date and treatment × date interaction; P < 0·001), but in general, FEC indicated that goat kids grazing ALF were less affected by GIN than kids grazing RCG or OGR. Research is needed to determine whether strategic energy supplementation would improve protein‐use efficiency and resilience to parasite infection when finishing meat goats on pastures managed for high forage nutritive value.  相似文献   

18.
Understanding the grazing conditions under which plant populations are limited by seed availability (seed limitation) is important for devising management schemes that aim to manipulate the establishment of weed and forage species. Seeds of three weed species (Cirsium arvense, C. vulgare and Rumex obtusifolius) and five forage species (Lolium perenne, Lotus uliginosus syn. L. pedunculatus, Paspalum dilatatum, Plantago lanceolata and Trifolium repens) were broadcast sown into L. perenne–T. repens pastures in Manawatu, New Zealand and five sheep‐grazing and two slug‐grazing (with and without molluscicide) treatments were imposed in a split‐plot design. Of the five sheep‐grazing treatments, four compared continuous grazing with rotational grazing at intervals of 12, 24 and 36 d in spring, with all four grazed under a common rotation for the remainder of the year. The fifth treatment was continuous grazing all year. Seed sowing increased seedling emergence of C. vulgare, L. perenne, P. lanceolata, R. obtusifolius and T. repens under all sheep‐ and slug‐grazing treatments, with differences in seedling densities persisting for at least 21 months. Seed sowing did not increase seedling densities of C. arvense, L. uliginosus or P. dilatatum. The effects of sheep‐grazing management on seedling emergence and survival were uncoupled. For the five seed‐limited species, seedling emergence was greater on pastures that were rotationally grazed during spring compared with those that were continuously grazed. However, seedling survival was lower in pastures grazed rotationally during summer, autumn and winter, so that after 21 months seedling numbers were greater on plots that were continuously grazed all year. Exclusion of slugs increased seedling recruitment of T. repens but had no impact on the other species. As weed and forage species responded in a similar way to sheep‐grazing management (increased under continuous, decreased under rotational), it is unlikely that the goals of reducing weed invasions and enhancing forage species establishment could be carried out concurrently in established pastures with the same management.  相似文献   

19.
Livestock grazing can be a means to maintain biodiversity in grasslands, but the outcome for vegetation structure and species composition depends on livestock type and grazing regime. This study aims at disentangling the effects of plant functional‐group abundance and livestock type on the above‐ and below‐ground biomass and N allocation in temperate pastures. We investigated the effects of cattle, sheep and mixed stocking on above‐ground biomass (AGB) and belowground biomass (BGB) and plant N pools in a replicated grazing experiment in two pasture community types with different plant functional‐group abundance (diverse vs. grass‐dominated swards). In the six treatments, AGB was reduced up to 80% compared with an ungrazed control. Cattle reduced AGB to a larger extent than sheep in diverse pastures (80 vs 44% reduction) while sheep grazing tended to do so in grass‐dominated pastures (57 vs 46% reduction); mixed stocking led to intermediate values. Grazing reduced AGB more than the N pool in AGB, thus lowering the biomass C/N ratio relative to the ungrazed control. Neither BGB nor the N pool in BGB differed between the grazing treatments and the control plots. We conclude that livestock type and functional‐group abundance are interacting factors that influence plant biomass and N pools in swards of managed temperate pastures. The contrasting biomass removal rates of cattle and sheep could be used to increase the structural heterogeneity and total plant species pool of pastures by keeping different livestock species in neighbouring patches.  相似文献   

20.
Ryegrass (Lolium perenne L.) is a putative turf and forage plant characterized as mainly outcrossing in which the extent of self‐fertilization and its consequences has not been investigated. In this study, selfed and half‐sib family seeds were obtained from ten clonally propagated ryegrass plants among which two were endophyte‐free (EF) and eight were endophyte‐infected (EI). Then, 20 seed populations plus two commercial varieties of Speedy and Vigor were sown and evaluated in a biennial experiment for their turf and forage characteristics. Selfing caused significant inbreeding depression for plant fresh and dry weight and leaf length and width in the first year for both EI and EF genotypes. In the second year, only leaf length remained depressed among these characters. Also, for the most growth, turf and reproductive traits, EI populations showed less depression. The presence of endophyte in self‐pollinated populations made an increasing effect for the number of seed per spike and days to heading, although seed weight was reduced. Some of the populations derived from self‐pollination and infected with fungal endophyte including S9 and S10 were even superior to the two commercial varieties in terms of both seed production and turf characteristics. However, for seed‐related characteristics including number of spikes per plant, seed weight and seed yield, EF populations including Speedy and Vigor were more reproductive than EI populations. It is concluded that selfing may increase the discrimination between EI and EF ryegrass plants because endophyte infection may mitigate the negative consequences of inbreeding depression in prone populations.  相似文献   

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