Two groups (n=39) of Romney breeding ewes were maintained under the same grazing management on either endophyte-infected (E+) or endophytefree (E-) perennial ryegrass pasture for two years (1997–1998) following a one-year equilibration period. The ewes were naturally mated in March each year and ovulation rate at 1st mating was measured, and conception and the number of lambs born and weaned were recorded. All ewes were weighed monthly and lamb growth rates were determined between birth and weaning. Mean mating date was delayed by 1.8 days (P<0.05) in the E+ ewes. There were no significant differences in any of the other reproductive parameters measured in either year. Grazing endophyte-infected pasture had a significant (P<0.001) negative effect on ewe liveweight, which appeared to be a result of reduced feed intake by the E+ ewes. Growth rate of twin- and single-lambs suckling ewes grazing E+ pasture were significantly (P<0.01) reduced in the second year of the trial but not in the first year. Differences in lamb growth rate may have been due to differences in ewe milk production. Ergovaline and lolitrem B levels in the E+ pasture were significantly higher in 1998 than they had been in 1997. Ewe and lamb performance in relation to endophyte toxin levels in the pasture is also discussed. Keywords: endophyte, ewe, lamb growth rate, Neotyphodium lolii, perennial ryegrass, reproductive performance
A case study of a Hawke’s Bay farm with a history of ryegrass staggers (RGS) and results of a survey of veterinarians from three regions are presented. A RGS outbreak in 1989 on the ‘Tunanui’ property at Sherenden resulted in the loss of 900 sheep and three cattle, with total costs estimated to be $61,000. There have been no severe outbreaks since then, despite similar climatic conditions occurring. The probable reason for this is a combination of improved awareness of RGS and conscious avoidance of the problems, and the indirect effects of other changes to farm management. The survey of veterinarians showed a rise in the prevalence of ryegrass endophyte related disorders in Manawatu and Waikato between the 1980s and 1990s, but no change for East Coast regions. Veterinarians spend very little time assisting clients with endophyte related problems, despite 41% of clients having problems. It is recommended that veterinarians provide more prevention advice to farmers, and farm management practices that successfully reduce RGS be promoted. Keywords: cattle, deaths, disorders, East Coast, farm, prevalence, remedies, ryegrass staggers, sheep, veterinarians
Ryegrass staggers (RGS) is a neurotoxic disease in ruminants. It is caused by the mycotoxin lolitrem B, found in endophyte-infected perennial ryegrass (Lolium perenne L.). This paper reviews genetic studies on the resistance of sheep to RGS at Ruakura. Genetic differences in susceptibility among sire groups were evaluated in lambs born in 1988–92 (Phase 1). Selection lines were then formed and responses to selection for resistance or susceptibility are described for the 1993–98 birth years (Phase 2). The incidence of RGS was recorded on a presence or absence basis from January to March or April each year, in experimental flocks with animals of known pedigree. For estimating genetic parameters (Phase 1), there were 3587 RGS records available from 2307 animals representing 232 sires. Clinical cases of RGS occurred in 17 of 25 contemporary groups, with incidences per group up to 16%. Estimates of heritability and acrossyear repeatability for RGS incidence were 0.068 ± 0.028 and 0.24 ± 0.05 respectively. Breeding value data were used at the beginning of Phase 2 to screen ewes, two-tooths and ewe lambs into resistant and susceptible selection flocks (lines). Breeding values were also used to select rams that were elite for RGS, and to allocate these to each line for mating. At least some natural RGS challenge was experienced by the resulting selection-line stock born in five of the six years of Phase 2. Susceptible-line lambs had a mean incidence of 39% clinical RGS cases over these five years, whilst the resistant-line lambs grazing the same paddocks had a much lower mean clinical RGS incidence (P<0.001) at 15%, a difference of 24%. Breeding ewes from the resistant RGS line also experienced significantly less clinical RGS than those in the susceptible RGS line (P<0.001). Evidence is presented from another experiment at Ruakura, in which selection pressure was applied for increased or decreased resistance to facial eczema. The facial eczema-resistant line was also more resistant to RGS than the facial eczemasusceptible line, suggesting that there is a common biochemical pathway explaining some of the resistance to both sporidesmin and lolitrem. Studies of the RGS selection flocks are being continued in order to investigate the underlying genetic mechanisms. The selection response so far indicates that genetic differences in RGS susceptibility can be achieved by using records collected under extensive conditions. Keywords: Lolium perenne, resistance, ryegrass staggers, selection, sheep
The health and production of sheep grazing perennial ryegrass with and without wild-type endophyte (Neotyphodium lolii) has been studied in several trials over a number of years. Lambs/ hoggets grazing predominantly perennial ryegrass swards with endophyte developed moderate to severe ryegrass staggers in summer and autumn, while those grazing endophyte-free ryegrass did not. Lambs/hoggets grazing ryegrass with endophyte also had more dags, lower growth rates, lower plasma prolactin levels, higher body temperatures and respiration rates under warm humid conditions. Most of these adverse responses were more severe in summer and autumn when endophyte toxin concentrations were highest. Many of these symptoms are similar to those described for the “autumn ill thrift” syndrome in New Zealand. Keywords: dags, endophyte, flystrike, growth rates, hyperthermia, Neotyphodium, perennial ryegrass, prolactin, ryegrass staggers, sheep
Sixteen short term tests of the effects of ryegrass (Lolium perenne L.) endophyte on milk production from dairy cows were carried out at Dairying Research Corporation (DRC) sites in Taranaki (1992/93) and Waikato (1993–1999). Increasing contamination of endophyte-free areas with volunteer endophyte-infected ryegrass could have modified milk production responses to endophyte in the first of two trials in the Waikato (1993– 1996). Test periods were in spring, summer and autumn. Significant effects of endophyte on milk production were detected on only 4 occasions. Small (<6%) reductions due to endophyte occurred in spring 1994, summer 1995/96 and spring 1997, and in autumn 1998 cows grazing pastures with high (H) levels of endophyte produced more milk than those grazing pastures with low (L) endophyte levels. Herbage levels of lolitrem B and ergovaline were low in spring 1994 and spring 1997 (<0.4 μg/ g DM) compared with peak levels in summer of 1.2 to 3.1 μg/g DM. Ryegrass staggers occurred in cows grazing H pastures in summer 1993/94 and summer/autumn 1994/95, but not when there was an endophyte effect in summer 1995/96. Herbage ergovaline levels and ambient temperatures were generally below critical levels for development of clinical heat stress in cattle, and cow rectal temperatures were unaffected by treatments. Overall effects of endophyte on milk production were considered to be small and inconsistent. Keywords: alkaloids, contamination, dairy cows, endophyte, ergovaline, lolitrem B, Lolium perenne, milk production, Neotyphodium lolii, perennial ryegrass, somatic cell counts
An on-farm trial was carried out at Te Hana, in Northland, to measure milk production responses in 2 groups of 16 spring-calving, 3-year-old Holstein-Friesian cows maintained throughout the trial on pastures with or without the ryegrass endophyte toxins, ergovaline and lolitrem B. The trial began in October 1997, with second calving cows balanced for calving date and production worth. Milk volumes of all cows were recorded for 10 consecutive days each month followed by a herd test in which milk volume, protein, fat and lactose contents were determined from milk samples. There were no differences in milk volume or milk solids production in the October and November measurement periods. In December, the group grazing toxin-free (–Ev) pastures produced 24% more milk than the group grazing toxincontaining (+Ev) pastures. These differences increased progressively as the trial proceeded, until terminated in mid-April. Throughout the trial period the –Ev group produced 23% and 19% more milk and milk solids, respectively, than the +Ev group. A rise in levels of the endophyte toxins in ryegrass coincided with the start of differences in milking performance. A toxin-free maize based supplement was fed to both groups during the January to March period to maintain the trial when pasture growth was insufficient. A negative correlation was found between milk production of the +Ev group in January and the prevailing temperature and humidity conditions during the night. Keywords: endophyte toxins, ergovaline, lolitrem B, milk production, Neotyphodium, Northland, ryegrass
Case studies of two Manawatu properties currently experiencing ryegrass staggers (RGS) are presented; a dairy farm and a run-off grazing both dairy heifers and intensive bull beef. Before its conversion from a sheep and cattle enterprise to dairying an outbreak of RGS was experienced in 1987. Tall fescue-based pastures were established to minimise the potential threat of RGS. In the intervening 12 years high endophyte ryegrass cultivars have been established and hotter, drier summers are being experienced in this region. Severe cases of RGS have been observed in the last three years. On the dairy farm in 1998/99, 21 cows were dried off in January due to severe RGS. The loss in production is impossible to measure. Sixteen heifers and weaner bulls died during that summer due to RGS and those alive were 35 kg LWT below target. Management options to reduce the effects of endophyte-related disorders include establishing non-toxic pastures such as tall fescue or forage crops to utilise during periods of the year when RGS can be experienced. While limited in cultivar choice at present, the use of novel endophytes provides long-term options for farmers wishing to reduce RGS yet still maintaining ryegrass pastures. Including herbaceous species such as chicory or plantain in pasture mixes will provide high quality summer forage and can dilute the effects of endophyte in the total daily intake. Keywords: bull beef, dairy cows, endophyte, heifers, perennial ryegrass, ryegrass staggers
Perennial ryegrass pastures infected with or free of the endophyte (Neotyphodium lolii) were compared for growth and health of young grazing cattle. Heat stress, indicated by excessive salivation, was observed on several occasions among cattle grazing endophyte-infected ryegrass, but there were no differences between groups in body temperature. Liveweight gains were generally slow and inconsistent. During one period of rapid liveweight gain in March–April 1997, heifers grazing endophytefree pastures gained 7 kg more than heifers grazing infected pasture. Taking data from three four-week grazing periods in summer and autumn, liveweight change of cattle grazing endophyte-free pastures showed a consistent advantage over cattle grazing endophyte-infected ryegrass. Significant differences in serum prolactin were recorded on two occasions, and on one day in February 1998 weaner bulls grazing infected ryegrass were breathing significantly faster than their counterparts on endophyte-free pasture. These results can be compared with previous reports that endophyte status of ryegrass pastures has little effect on grazing cattle, and contrast with the published literature for tall fescue. Keywords: liveweight gain, Neotyphodium lolii, perennial ryegrass, ryegrass endophyte
Neotyphodium spp. fungi in pasture grasses synthesise a diverse range of metabolites. In this report, recent progress in extending knowledge of the diversity of endophyte metabolites is reviewed, in particular the elucidation of indole-diterpenes and ergot alkaloids. Some 20 indole-diterpenes have been identified from N. lolii-infected perennial ryegrass, and several ergot alkaloids additional to ergovaline have been identified in perennial ryegrass and other grasses infected with Neotyphodium spp. endophytes. While lolitrem B, ergovaline, and peramine remain significant factors in understanding the biological activity of N. loliiinfected perennial ryegrass, a more complex and complete view of endophyte chemical ecology must now be developed. Keywords: chanoclavine-I, dehydroergovaline, endophyte, ergine, ergot alkaloid, indolediterpene, Neotyphodium spp., perennial ryegrass, tall fescue
The mycotoxins lolitrem B (responsible for ryegrass- staggers), and paxilline have a common moiety and are well known for their ability to cause tremoring in animals. Little is known of their other effects in ruminants and we investigated these in sheep, on electromyographic (EMG) activity of gastrointestinal smooth muscle of the reticulum, rumen, abomasal antrum and duodenum and on blood pressure, heart rate, respiration and body temperature. Both mycotoxins induced tremor and caused marked increases in respiratory rate, heart rate and blood pressure, but had relatively little effect on body temperature. Increases in blood pressure preceded substantial rises in heart rate, indicating a peripheral vasoconstrictive effect. Both mycotoxins had variable excitatory and inhibitory effects on the antrum and duodenum, but had consistent and profound effects on activity of the reticulorumen with a similar time course to their characteristic effects for paxilline and lolitrem B respectively, on the induction (2 and 30 minutes) and the duration (2–3 h and 8–12 h) of tremoring. The effects included an inhibition of the vagallydependent cyclical A and B sequences of contraction of the reticulorumen and an excitation of intrinsic activity including “chaotic” activity of the reticulum. Excitatory effects of the tremorgens were partially blocked by atropine, indicating some but not all, excitatory effects on the reticulorumen arise from stimulation of muscarinic cholinoceptors and it is possible this and other excitatory effects may be mediated through calcium-activated high conductance potassium channels. It is concluded tremorgens have widespread effects on the respiratory, cardiovascular and digestive systems. The intensity and duration of the effects with lolitrem B, indicate substantial disruption of digestion may occur with its ingestion on grazing endophyte-infected pasture. Keywords: cardiovascular, electromyograph activity, endophyte, gastrointestinal, lolitrem B, mycotoxins, paxilline, respiration, reticulorumen, temperature
Several ergot alkaloids additional to ergovaline have been identified in perennial ryegrass and other grasses infected with Neotyphodium spp. endophytes. The identification of the ergot alkaloids ergine, chanoclavine-I and dehydroergovaline, from New Zealand samples of endophyte-infected tall fescue and perennial ryegrass is reported and discussed. Keywords: chanoclavine-I, dehydroergovaline, endophyte, ergine, ergot alkaloid, Neotyphodium spp., ryegrass, tall fescue
Epichloë endophytes are an important group of filamentous fungi that confer on the grass host a range of biological benefits. However, endophyte synthesis of ergopeptine and indole-diterpene mammalian toxins in pasture grasses is detrimental to livestock grazing on that forage. The molecular cloning of the genes involved in the biosynthesis of these toxins will enhance our ability to maximise the beneficial attributes of this mutualistic association through the availability of DNA probes to screen and select for desirable endophytes and through our ability to genetically modify endophytes. Genes involved in the biosynthesis of both classes of alkaloids have recently been cloned from Claviceps purpurea and Penicillium paxilli. In both cases the genes are organised in large clusters; a feature that will facilitate a complete genetic analysis of each pathway and provide probes for isolating homologous genes from Epichloë endophytes. This paper reviews recent research developments on the molecular biology of these two pathways. Keywords: Epichloë endophytes, ergopeptines, gene cloning, gene manipulation, indole-diterpenes
This paper provides a brief introduction to the biology of endophyte-ryegrass associations and summarises results of our recent research into the interactions between host and endophyte. Specific topics include: (i) interactions between fungus and plant necessary for their successful association, (ii) the levels of biological activity of endophyte hyphae in the plant, and (iii) the potential of endophyte- ryegrass associations to protect themselves against accumulation of detrimental mutations in the endophyte and to benefit from beneficial mutations in the endophyte. Keywords: clonal selection, compatibility, endophyte-plant interaction, endophyte metabolism, endophyte-plant signalling, evolution, mutation, Neotyphodium, reporter gene, synchronous growth
The ryegrass endophyte/plant interaction produces a number of toxic metabolites responsible for a range of toxicoses including ryegrass staggers. Although lolitrem B has long been considered the toxin responsible for ryegrass staggers in farm animals, it is only recently that we have demonstrated that oral administration of the pure toxin causes tremors in mice consistent with the symptoms of ryegrass staggers. Various levels of the toxin were incorporated into the diet of mice and tremor response measured regularly. Mice were very susceptible to the tremorgenic action of lolitrem B with a dose of only 1.1 mg/kg per day being sufficient to induce a tremor response. Analysis of faeces from a dosed mouse showed that approximately 40% of the toxin ingested was excreted unchanged. The profile of tremor response shows that tremors build up over a 24-hour period and then reach a dose dependent plateau suggesting that toxin turnover reaches a steady state. In experiments designed to test the possibility that tremorgens bind to specific receptors in the brain, mice were injected with the 14C-labelled tremorgen, paxilline. Paxilline was chosen as it is similar in structure and possible action to lolitrem B and could be more easily prepared with an isotopic label. Following injection of 14C-paxilline to mice their brains and spinal cord were sectioned and analysed for 14C content. Localised binding was not detected but rather an even distribution of isotope was observed. This is probably due to the lipophilicity of the tremorgens, which distribute randomly throughout the fatty brain matrix, masking any binding to specific regions or receptors. This study showed, however, that only a minute proportion of the administered tremorgen reached the brain and spinal cord, indicating that, if this is the site of action, the receptors involved in the initiation of staggers are extremely sensitive to the tremorgens. Keywords: endophyte, lolitrem, Lolium perenne, mycotoxin, Neotyphodium lolii, neurotoxin, oral dosing, ryegrass staggers, tremor, tremorgen
Ryegrass/endophyte associations have been developed which produce peramine, but not the endophyte toxins ergovaline or lolitrem B. Sheep grazing these ryegrasses in small paddocks and in a systems trial over three years gained weight as rapidly as those grazing endophyte-free ryegrass, and showed none of the adverse responses associated with grazing ryegrass naturally infected with wild-type endophyte (Neotyphodium lolii). Growth rates, rectal temperatures, respiration rates, serum prolactin concentrations, ryegrass staggers scores and scores for dag burdens were equivalent for the selected endophyte and nil endophyte treatments, whereas sheep grazing the wild-type endophyte treatment were adversely affected for all parameters. This was reflected in calculated gross margins for the systems trial of only $605 per hectare for the wild-type endophyte treatment compared with over $700 per hectare for each of the other treatments. To date there have been no conclusive studies of non-toxic endophyte with cattle. Keywords: AR1, dags, endophyte, ergovaline, liveweight gain, lolitrem B, Lolium perenne, Neotyphodium, peramine, perennial ryegrass, prolactin, sheep
This paper reviews how new pastures may become contaminated with perennial ryegrass (Lolium perenne) infected with wild-type fungal endophytes (Neotyphodium lolii). These wild-type endophyte strains may be toxic to domestic livestock. Sources are from seed (natural reseeding, buried seed, sown seed, in dung, hay, carried on farm machinery) and survival of existing infected ryegrass plants. In particular, seed in soil and dung are reviewed. Contamination may occur both pre- and postestablishment. It is recommended that steps should be taken to minimise contamination from all sources when establishing new pastures. Although normal establishment practices for successful rapid establishment of weed-free pastures (e.g., cropping, fallow, herbicides) will minimise the risk of contamination, a number of cases highlight that extra time (e.g., 18–24 months planning rather 6– 12 months) and consideration of all sources of contamination is needed to minimise risk. Once established, further measures should be taken to prevent seed being transferred in dung or hay. This has implications when establishing pastures with endophyte-free ryegrasses, ryegrasses with selected non-toxic endophytes, a new ryegrass cultivar, or other grasses (e.g., tall fescue), whether for grazing by animals or for seed production. Keywords: endophyte, endophyte survival, faeces, Lolium perenne, natural reseeding, Neotyphodium lolii, pasture establishment, perennial ryegrass, seed burial, seed survival, tall fescue
A national series of six small plot trials were sown in 1996 and four in 1997 to evaluate the performance of six novel fungal endophytes in Grasslands Nui perennial ryegrass. These endophytes do not produce the mammalian toxins, ergovaline and lolitrem B, but produce peramine, a feeding deterrent to the major ryegrass pest, Argentine stem weevil (ASW). Trials included the naturally occurring endophyte (wild-type) which produces both toxins, and an endophyte-free (nil) treatment. Pasture production was measured regularly and samples were taken at least once each summer–autumn from all trials for assessment of ASW damage. Black beetle larval damage was recorded on three trials. The toxin-free endophytes, AR1, AR12, AR22 and the wild-type were equally effective at reducing ASW adult feeding and larval damage significantly below that which occurred in nil treatments. Ryegrass infected with AR1, AR12, AR22 and the wild-type endophyte was damaged less by black beetle larvae than ryegrass without endophyte. The effect of AR24 on insect damage was variable and two other toxin-free endophytes, AR17 and AR506, which had low infection rates, seldom reduced either ASW or black beetle damage. Yield differences between treatments were found on two of 21 sampling occasions between October and December and 12 of 30 sampling occasions between January and April. During summer–autumn, wild-type, AR1, AR12 and AR22 gave higher ryegrass yields than the nil, AR17 and AR506 treatments. In the second year of the 1996-sown trials, productivity of ryegrass with AR1 in the summer–autumn tended to be lower than that of the wild-type with significant differences occasionally occurring. Yield differences were correlated with either ASW or black beetle damage in North Island trials and with percent endophyte infection at all sites. Differences in yield at Lincoln, Canterbury, were attributed to pasture mealy bug. Three conclusions were drawn from these results: 1. Endophytes are very important for maximising ryegrass yield during summer and early autumn. 2. The effect of endophytes on yield is at least partly due to the insect resistance they impart. 3. The field performance of three toxin-free endophytes, AR1, AR12 and AR22, equalled that of the wild-type in terms of increased insect resistance but did not always match it in plant growth. Keywords: AR1, Argentine stem weevil, black beetle, endophyte strain, ergovaline, insect damage, lolitrem B, Neotyphodium lolii, ryegrass yield
Strains of perennial ryegrass (Lolium perenne L.) endophyte (Neotyphodium lolii) from nature can be selected by analysis of the alkaloid profiles in plants from diverse seed collections. Lolitrem B, ergovaline, and peramine are the alkaloids of primary interest. The selected endophytes can be cultured and transferred into improved cultivars or breeding lines to reduce or eliminate grazing animal toxicoses while significant plant protection qualities can be maintained. Because the endophytes are transmitted only through seed, stable infections with selected endophytes in pastures can be achieved. Keywords: alkaloids, endophyte, ergovaline, lolitrem, Neotyphodium lolii, peramine, perennial ryegrass
Three lamb growth experiments were carried out at Massey University, Palmerston North, from 1995 to 1998 to evaluate the nutritive value and endophyte (Neotyphodium lolii) status of a new perennial ryegrass (Lolium perenne L.) cultivar (Aries HD). Aries HD was specifically selected for improved organic matter digestibility over summer and early autumn. Lamb liveweight gain on ‘Aries HD’ compared to a control cultivar ‘Yatsyn 1’ perennial ryegrass was higher in the summer of 1995/96 (104 vs 84 ± 4.6 g/day, P=0.1028), similar in two consecutive summers, 1996/97 (116 vs 111 ± 5.1 g/day, P=0.6542), and 1997/98 (71 vs 73 g/day ± 10.6 g/day, P=0.7350). The nutritive value (invitro organic matter digestibility, neutral detergent fibre and nitrogen content) of Aries HD and Yatsyn 1 pastures was similar. Lambs grazing Yatsyn 1 were more severely affected by ryegrass staggers than lambs grazing Aries HD, although the concentrations of lolitrem B in grazed herbage were similar. The concentration of ergovaline in Aries HD in association with endophyte was about half that in Yatsyn 1 in association with endophyte. Ergovaline may have acted synergistically to increase the toxicity of lolitrem B and the severity of staggers in lambs grazing Yatsyn 1 pastures. There was some indication that heat stress symptoms were more severe in lambs forced to graze lower into the sward. The effect of management and alkaloid concentration is likely to have a larger impact on lamb performance than small differences in nutritive value between cultivars of highendophyte perennial ryegrass. Keywords: alkaloids, animal performance, Aries HD, endophyte, heat stress, Lolium perenne, Neotyphodium lolii, perennial ryegrass, ryegrass staggers, Yatsyn 1
Emergence of volunteer perennial ryegrass (Lolium perenne L.) from seed buried in soil may contribute to the ingress of ryegrass in newly sown pastures. To investigate this, ryegrass seed infected with fungal endophyte (Neotyphodium lolii) was buried in nylon bags under pasture at two depths and at two sites (Palmerston North, Lincoln) in early/mid-autumn 1998. Seed bags were removed from the soil at intervals over the course of one year to determine seed viability and presence of endophyte in seedlings. Viability of seed declined rapidly to be 10% 3 months after burial. Further decline in viability was less, so that 12 months after burial 4% of seeds were still viable. Endophyte viability also declined, from 58% infection of seedlings at the time of burial to 21% at 12 months. This was at a slower rate than the decline in seed viability and from what might have been predicted from seed storage experiments. Viability of seed buried at 10 cm was greater than that buried at 3 cm (e.g., means, 10% and 1% after 6 months, respectively). This has implications for cultivation practices before pasture establishment. Seed buried at Lincoln maintained higher viability than seed buried at Palmerston North (e.g., means, 6% and 4% after 6 months, respectively), which was associated with drier soil conditions at Lincoln. Survival of buried seed may therefore be of greater importance in summer-dry east coast regions, compared with moist west coast environments or in wet years. The significance of buried ryegrass seed will depend on the numbers involved, but after 12 months there were still viable seeds left in the soil and some of these were infected with endophyte. This is important for pastures sown with ryegrass that is free of endophyte or infected with a selected endophyte, and for slower establishing grass species such as tall fescue. Keywords: endophyte, endophyte survival, Lolium perenne, Neotyphodium lolii, perennial ryegrass, seed burial, seed survival
Background on endophytes Endophyte is a fungus, which exists inside individual ryegrass plants, and reproduces through infecting ryegrass seed. Endophytes are very widespread in New Zealand pastures, being present in 70% of ryegrass tillers in Southland, and 99% in the upper North Island. The presence of endophyte confers benefits to the host ryegrass plant, inhibiting its susceptibility to grazing by: • domestic animals. • above ground insects, particularly. (a) Argentine stem weevil (b) Black beetles (c) Mealy bug. General awareness of its existence, and understanding of its role, began in the 1980s, and is still expanding. Knowledge of its existence and impacts now allow us to better explain the reasons for “inexplicable” results from scientific trials before 1980. It may also be a prime cause of summer “ill thrift”. The endophyte responsible for ryegrass staggers in cattle, sheep, deer and horses occurs in perennial ryegrass and some hybrid ryegrass plants. Endophytes that have toxic effects on grazing animals also occur in other grass species, for example, the endophyte in roadside tall fescue that causes “fescue foot”. However, commercial cultivars of tall fescue sold in New Zealand do not contain toxic endophyte.
Ryegrass pastures in New Zealand are usually infected with the ryegrass endophyte (Neotyphodium lolii). The endophyte provides protection from invertebrate attack, discourages overgrazing by livestock and perhaps confers other advantages enhancing ryegrass persistence. The endophyte lifecycle is completed within the plant, and transmission is uniquely through the grass seed. Within the plant, the endophyte synthesises a range of compounds, some of which have been identified as responsible for known endophyte effects on pasture invertebrates and on livestock. The concentrations of these compounds vary in different parts of the plant, with plant age and in response to environmental influences. While endophyte has wellknown adverse effects on livestock (reviewed elsewhere in this volume), it contributes positively to grassland productivity in New Zealand. Keywords: endophyte, Lolium, Neotyphodium lolii, pest resistance, ryegrass
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