ABSTRACT

In identifying endophytes for use in pastures in New Zealand there have been two strategies used, either exclusion of ergopeptine and lolitrem alkaloids or, retaining some ergopeptine expression to enhance the stability of natural defences against invertebrate pests. Both have their strengths and weaknesses. It is a matter of balancing these to ensure the end-user has access to a product that satisfies their needs – a persistent pasture with low to nil animal toxicity in terms of animal production and welfare. The range and intensity of ergot alkaloids in grazed pasture on both pasture and ruminants is reviewed, with emphasis on New Zealand. Ergot alkaloids associated with pasture are produced by associations between certain Epichloë endophyte strains and temperate grasses. Ergot alkaloids have been shown to improve persistence of pasture through providing resistance/deterrence to insect pests as well as deterring grazing animals. However, ergovaline is toxic to grazing animals. Some commercially available ryegrass-endophyte associations can produce ergovaline concentrations close to those found in associations between ryegrass and the standard endophyte. It is feasible to eliminate ergot alkaloids from pasture grasses in New Zealand as endophyte strains are commercially available that do not express ergovaline and yet still provide excellent pest resistance.

摘要

在确定用于新西兰牧场的内生菌时，使用了两种策略，一种是排除麦角肽碱和洛利曲林生物碱，另一种是保留一些麦角肽碱表达以增强对无脊椎动物害虫的天然防御的稳定性。两者都有自己的长处和短处。平衡这些问题以确保最终用户能够获得满足其需求的产品——在动物生产和福利方面具有低至零动物毒性的持久牧场。回顾了牧场和反刍动物放牧牧场中麦角生物碱的范围和强度，重点是新西兰。与牧场相关的麦角生物碱是由某些Epichloë之间的关联产生的内生菌菌株和温带草。麦角生物碱已被证明可以通过对害虫提供抗性/威慑以及威慑放牧动物来提高牧场的持久性。然而，麦角瓦林对放牧动物有毒。一些市售的黑麦草-内生菌联合产生的麦角缬氨酸浓度接近于黑麦草和标准内生菌联合产生的浓度。在新西兰的牧草中消除麦角生物碱是可行的，因为内生菌菌株是市售的，它们不表达麦角缬氨酸，但仍具有出色的抗虫性。