Ryegrass Endophyte: An Up-to-Date Review of its Effects P.V.Rattray June 2003 Report produced by Meat and Wool Innovation Ltd under contract to Merino New Zealand Inc
Ryegrass Endophyte: An Up-to-Date Review of its Effects P.V. Rattray June 2003 Report produced by Meat and Wool Innovation Ltd under contract to Merino New Zealand Inc
CONTENTS Page No. 1.0 POPULAR SUMMARY 3 2.0 REVIEW:ENDOPHYTES IN NZ PASTURES 44 2.3 Pastere Ylroution tes on various aspects of 6 2.4 Pest Protection Persistence:A Summary of the Main Events 2.5 Alkaloid Metabolites Produced by Endophytes 2.6 Variation in Alkaloid Concentrations 89 2.7 PRG Endophytes Animal Health Effects 2.9 Main Chemical Compounds 20 ese arch ent 113131415617 214 cted Stra oxic Endophyte Strains s in the F talian Hybrid Ryeg asses 9 216 Tall Fesc 217 Control Prevention of Endotoxicoses 20 2.18 Conclusion 23 CONCLUSIONS 24 4.0 REFERENCES 25 PAGE2
CONTENTS Page No. 1.0 POPULAR SUMMARY 3 2.0 REVIEW: ENDOPHYTES IN NZ PASTURES 4 2.1 Introduction 4 2.2 Endophyte in NZ Pastures 4 2.3 The Effects of Endophytes on Various Aspects of Pasture Yield & Production 5 2.4 Pest Protection & Persistence: A Summary of the Main Events 7 2.5 Alkaloid Metabolites Produced by Endophytes 8 2.6 Variation in Alkaloid Concentrations 9 2.7 PRG Endophytes & Animal Health Effects 11 2.8 Summary of the Main Chemical Compounds 13 2.9 Cattle Research 13 2.10 Horse Research 14 2.11 Seed Management 15 2.12 Endophyte Biology 16 2.13 Selection of Non-Toxic Endophyte Strains 17 2.14 Selected Strains in the Field 17 2.15 Italian & Hybrid Ryegrasses 19 2.16 Tall Fescue 19 2.17 Control & Prevention of Endotoxicoses 20 2.18 Conclusion 23 3.0 CONCLUSIONS 24 4.0 REFERENCES 25 PAGE 2
1.0 POPULAR SUMMARY Most ryegrass based pastures grazed by Merinos will contain endophyte. Endophytes are fungi that exist inside plants and are transferred via seed. Endophyte exists in a normal symbiotic relationship with ryegrass protecting it from Insect attack and offering other advantages. Endophytes produce a wide range of compounds including peramine,lolitrem B and ergovaline. Peramine offers some protection to the plant from insect attack,especially argentine stem weevil. Lolitrem B is a neurotoxin causing ryegrass staggers in animals. Ergovaline lowers blood prolactin levels and causes heat stress. Some of the above compounds,in combination with other unidentified compounds. depress intake,liveweight gain and cause scouring and dags in sheep. Non-toxic strains of endophyte have been selected. 。 The mo eiecsomgan9anenasrsvanoBcece。 is AR1 which produ Is aval eoneaantian .a number of prevention and control measures against the toxins have been tried but the only one offering complete protection is to replace the resident ryegrass pastures with AR1 ryegrass. Establishment of AR1 requires a spray/crop or double spray treatment to reduce toxic of wild occur after three or four years and precautions PAGE3
1.0 POPULAR SUMMARY • Most ryegrass based pastures grazed by Merinos will contain endophyte. • Endophytes are fungi that exist inside plants and are transferred via seed. • Endophyte exists in a normal symbiotic relationship with ryegrass protecting it from insect attack and offering other advantages. • Endophytes produce a wide range of compounds including peramine, lolitrem B and ergovaline. • Peramine offers some protection to the plant from insect attack, especially argentine stem weevil. • Lolitrem B is a neurotoxin causing ryegrass staggers in animals. • Ergovaline lowers blood prolactin levels and causes heat stress. • Some of the above compounds, in combination with other unidentified compounds, depress intake, liveweight gain and cause scouring and dags in sheep. • Non-toxic strains of endophyte have been selected. • The most promising is AR1 which produces peramine and protects the plant from insect attack with no ill effects on grazing animals. It is available commercially. • A number of prevention and control measures against the toxins have been tried, but the only one offering complete protection is to replace the resident ryegrass pastures with AR1 ryegrass. • Establishment of AR1 requires a spray/crop or double spray treatment to reduce toxic seed. • Ingress of wild type ryegrass can occur after three or four years and precautions should be taken to prevent seed entry. PAGE 3
2.0 REVIEW:ENDOPHYTES IN NZ PASTURES 2.1 Introduction Perennial ryegrasses(PRG)is the most widely sown species in NZ pastures and has 20s(Hunt Easton,1989).However,as late as 980,the discover that the e dophytic fungus,Neotyph m,caus d ryegrass 981)and prote e plant from Arge stidge et al. a982 total has also enab understanding The endophytic fungi in PRG and tall fescue had been described in 1933(Sampsor 1933)and further studied in the 1940s by NZ scientists (Neill,1941),and the possibility that they caused livestock disorders was raised and investigated(Cunningham,1958) However,the experiments failed to make the suggested link,and another 20 years passed before the significance of the endophytes was established. There was a considerable amount of serendipity about the crucial initial discoveries (Easton et al.,2001).Since then,endophyte research has been focused and multi USA rcangnrcp aisciplinary e etaeneatanePi monium loli,howeve r&Easton pers.comm.)on the basis of the alkaloids produced(Glenn Bacon,1997). 2.2 Endophyte in New Zealand Pastures Perennial ryegrass (Lolium perenne)is naturally infected with the endophyte Neotyphodium loli,but other endophytic fungi are also regularly found in perennia ryegrass(Latch et al.,1984).The influence of the latter on the pasture-livestock system is unknown and probably small They are not considered in this discussion,and the word "endophyte"refers here to N.lolii or related species in other grass hosts d to be 1992.ash Europe Lewis 1997 vas first n ago (Neill,1940).Other era and ecies are similarly ophytes.notably tall fescue( gel et al. 1987). PAGE4
2.0 REVIEW: ENDOPHYTES IN NZ PASTURES 2.1 Introduction Perennial ryegrasses (PRG) is the most widely sown species in NZ pastures and has been intensively researched since the 1920s (Hunt & Easton, 1989). However, as late as 1980, the discoveries that the endophytic fungus, Neotyphodium lolii, caused ryegrass staggers (Fletcher & Harvey, 1981) and protected the plant from Argentine stem weevil (ASW) (Prestidge et al., 1982) have required a total re-examination of all we thought we knew about ryegrass pastures. Endophyte research has also enabled us to revise our understanding of tall fescue. The endophytic fungi in PRG and tall fescue had been described in 1933 (Sampson, 1933) and further studied in the 1940s by NZ scientists (Neill, 1941), and the possibility that they caused livestock disorders was raised and investigated (Cunningham, 1958). However, the experiments failed to make the suggested link, and another 20 years passed before the significance of the endophytes was established. There was a considerable amount of serendipity about the crucial initial discoveries (Easton et al., 2001). Since then, endophyte research has been focused and multidisciplinary. Another feature of the work has been the importance of international contacts, and in particular the close and very useful interchange with research groups in the south east of the USA (Easton et al., 2001). When the endophyte of PRG was first discovered it was named Acremonium lolii, however it was later reclassified as Neotyphodium lolii (Fletcher & Easton pers. comm.) on the basis of the alkaloids produced (Glenn & Bacon, 1997). 2.2 Endophyte in New Zealand Pastures Perennial ryegrass (Lolium perenne) is naturally infected with the endophyte, Neotyphodium lolii, but other endophytic fungi are also regularly found in perennial ryegrass (Latch et al., 1984). The influence of the latter on the pasture-livestock system is unknown and probably small. They are not considered in this discussion, and the word “endophyte” refers here to N. lolii or related species in other grass hosts. Ryegrass collected from old pastures throughout NZ has regularly been found to be infected with N. lolii (Prestidge et al., 1985; Wedderburn et al., 1989; Widdup & Ryan, 1992), as has ryegrass collected in Europe (Lewis et al., 1997). Endophyte was first noted in ryegrass in NZ 60 years ago (Neill, 1940). Other grass genera and species are similarly infected with related endophytes, notably tall fescue (Festuca arundinacea) (Siegel et al., 1987). PAGE 4
New Zealand experience is that perennial ryegrass in most old pastures is normally infected at very high frequency.However,in the south of NZ,infection rates are lower and some old pastures are nearly free 0f50 two vere less cted,but 29 tha ted perenni ryegras naopnyte (Piggot New Zealand pastures have higher levels of infection than those studied overseas.Of 54 onulations collected in north est Spain,15 were free of endophyte (Oliveira Castro 1998).and only 12 populations were 60%or more infected.Similar results were observed with French populations(Ravel et al.,1994).These infection levels are lower than those observed in southern NZ(Widdup Ryan,1992). 2.3 The Effects of Endophvte on Various Aspects of Pasture Yield Production Endophyte is essential to the thrift of perennial ryegrass pastures in NZ because it ryegrass nvertebra ests ASW 1982 (Mortime d tidge ely to d or Hunt.1983) those ent are pr at al rass stems bore less vigo ously into infected plants (Prestidge Gallag er,1988) observed to be dar ed in late summ in swards but was observed in infected swards (Popay&Mainland 1991).Under pressure from ASW,the frequency of endophyte infection increases rapidly as non-infected plants die and are replaced by expansion of infected plants (Hume Brock,1997;Prestidge et al.,1984). ASW has been shown to be an important factor in pasture failure in Canterbury (Goldson 1982)and much of the North Island(Barker et al.,1984b).Yield responses of 50-60%in mixed ryegrass-wnite insectici 1982 1n19 pastu 1991) was estimated a costi (FI it ophyte was shown t pro seed ilit genetic or varietal diffe 1982,and thougn Endophvte also protects perennial n rass from other invertebrates (Prestidge Ball 1993).Black beetle (Heteronychus arator)is intermittently a serious pest in northern NZ (East et al.,1981).Endophyte-free ryegrass can be quickly destroyed by black beetle (Lee et al.,1982),but endophyte deters feeding by the adults,and egg and larval numbers are reduced(Ball Prestidge,1992).Various nematode species,some endo-parasitic. others free-living in the root zone,are found in ryegrass pastures,and there is some evidence that populations are affected by endophyte infection (Eerens et al., 1998b Stewart et al.,1993).There is very little NZ information on the importance of grass in pastures (Watson et al., 1986, Yeates Prestidge, 1986 sture m aly bug (B s poae)is an &Bal,1999 Mealy bug presence is trivial n pasture PAGE 5
New Zealand experience is that perennial ryegrass in most old pastures is normally infected at very high frequency. However, in the south of NZ, infection rates are lower, and some old pastures are nearly free of endophyte (Widdup & Ryan, 1992). Of 50 populations examined, two were less than 20% infected, but 29 populations were more than 60% infected. Naturally occurring hybrid ryegrass may also be infected with the perennial ryegrass endophyte (Piggot et al., 1988). New Zealand pastures have higher levels of infection than those studied overseas. Of 54 populations collected in north-west Spain, 15 were free of endophyte (Oliveira & Castro, 1998), and only 12 populations were 60% or more infected. Similar results were observed with French populations (Ravel et al., 1994). These infection levels are lower than those observed in southern NZ (Widdup & Ryan, 1992). 2.3 The Effects of Endophyte on Various Aspects of Pasture Yield & Production Endophyte is essential to the thrift of perennial ryegrass pastures in NZ because it protects ryegrass from invertebrate pests, notably Argentine stem weevil (ASW) (Listronotus bonariensis) (Mortimer & di Menna, 1983; Prestidge & Ball, 1993; Prestidge et al., 1982). Adult ASW are less likely to feed on infected ryegrass (Barker et al., 1984d; Rowan & Gaynor, 1986). Less eggs and larvae are present in infected swards (Gaynor & Hunt, 1983), those present survive less well (Barker et al., 1984c) and larvae attacking ryegrass stems bore less vigorously into infected plants (Prestidge & Gallagher, 1988). In Manawatu, 70% of tillers were observed to be damaged in late summer in endophyte-free swards but negligible damage was observed in infected swards (Popay & Mainland, 1991). Under pressure from ASW, the frequency of endophyte infection increases rapidly as non-infected plants die and are replaced by expansion of infected plants (Hume & Brock, 1997; Prestidge et al., 1984). ASW has been shown to be an important factor in pasture failure in Canterbury (Goldson, 1982) and much of the North Island (Barker et al., 1984b). Yield responses of 50-60% in mixed ryegrass-white clover swards were achieved by protecting from ASW with insecticide (Kain et al., 1982). In 1991, pasture damage by ASW was estimated as costing NZ $46-$200m annually (Prestidge et al., 1991). Before endophyte was shown to provide protection, it had been noted that different seed lines of perennial ryegrass differed in their vulnerability to attack (Kain et al., 1982), and this was thought to indicate genetic or varietal differences. Endophyte also protects perennial ryegrass from other invertebrates (Prestidge & Ball, 1993). Black beetle (Heteronychus arator) is intermittently a serious pest in northern NZ (East et al., 1981). Endophyte-free ryegrass can be quickly destroyed by black beetle (Lee et al., 1982), but endophyte deters feeding by the adults, and egg and larval numbers are reduced (Ball & Prestidge, 1992). Various nematode species, some endo-parasitic, others free-living in the root zone, are found in ryegrass pastures, and there is some evidence that populations are affected by endophyte infection (Eerens et al., 1998b; Stewart et al., 1993). There is very little NZ information on the importance of grassassociated nematodes in pastures (Watson et al., 1986; Yeates & Prestidge, 1986). Pasture mealy bug (Balanococcus poae) is an insect frequently present in pastures but of unknown importance. It is sensitive to the presence of endophyte (Pearson, 1989; Pennell & Ball, 1999). Mealy bug presence is trivial in pastures intensively infected with PAGE 5