Lester Ronald Fletcher

The exploitation of epichloae endophytes for agricultural benefit

Epichloae endophytes of family Clavicipitaceae (comprising genera Epichloë and Neotyphodium) are fungal symbionts of Pooideae grasses. The associations formed, range from mutually beneficial to antagonistic and the nature of this relationship is dependent upon the importance of vertical (via host seeds) versus horizontal (ascospore mediated) transmission of the fungus. These endophytes can enhance their hosts’ survival through protection from abiotic and biotic stresses and can thus be utilized in an agricultural context. Animal-safe grass-endophyte associations that confer bio-protective properties for increased pasture persistence and productivity have been developed and commercialized. One of the crucial drivers underpinning the selection of epichloae strains for commercial development is endophyte derived bioactivity. The potential of next generation endophytes is determined by testing a number of attributes such as agronomic fitness, animal and food safety as well as compatibility with host plants of interest. Strategic research supports these activities by focusing on elucidating mechanisms of compatibility between host and fungal symbiont, as well as investigating other molecular drivers of symbiosis such as siderophore mediated iron-uptake, fungal signalling, fungal growth in host plants and fungal secondary metabolism. This review weaves together the different strands of multidisciplinary research aimed at ultimately exploiting epichloae endophytes for increased pasture performance.

The Evaluation and Use of Endophytes for Pasture Improvement

Forage plant improvement has been achieved through plant and family selection, leading to the identification and multiplication of genetically superior individuals (Pederson and Sleper, 1993). Objectives of pasture improvement have included higher and more reliable annual and seasonal herbage production, and also such factors as reduction or elimination of antiquality factors and improved tolerance or resistance to diseases and pests. Breeders have pursued two strategies with regard to edaphic stress. Usually they have sought a broad adaptability, but in some cases have sought adaptation to defined environmental niches, particularly if it is perceived that tolerance of stress is negatively correlated with productivity in its absence. Forage quality, understood in terms of ability to deliver digestible mineral and organic nutrients to the grazing animal, is an objective of growing importance.

Evaluating the performance of endophytes in farm systems to improve farmer outcomes – a review

Abstract. The main plant species relied on for forage supply to grazing animals in New Zealand and south-eastern Australia is perennial ryegrass (Lolium perenne L.). Perennial ryegrass has evolved with a fungal endophyte (Neotyphodium lolii, Latch, Christensen & Samuals) that occupies intercellular spaces, and is nourished by its host. The endophyte (referred to as standard or wild-type) provides the plant with protection from a range of insect pests by producing alkaloids, some of which are also toxic to grazing animals, causing ryegrass staggers and/or exacerbating heat stress. Over the last 20 years naturally occurring perennial ryegrass endophytes have been found in Europe that produce less of the alkaloids that cause animal health problems but have similar or enhanced effects as the standard endophyte on deterring insect attack on infected plants, when introduced into New Zealand and Australian-bred ryegrasses. This review provides a summary of endophyte research in New Zealand from the perspective of insect pests, plants (particularly perennial ryegrass) and the animals grazed on ryegrass-dominant pastures. The protocols used to evaluate perennial ryegrass/endophyte associations over the past 30 years are also discussed. Future testing of new grass/endophyte associations should include the utilisation of more environments for agronomic and entomological experiments; routinely carrying out small animal toxicology assays, and the running of short-term indoor feeding experiments with sheep and cows. Implementation of these changes provides the minimum requirements for strengthening the evaluation of new endophyte associations so farmers using these technologies, gain optimal benefits from their adoption.

Seasonal distribution of loline alkaloid concentration in meadow fescue infected with Neotyphodium uncinatum

Loline alkaloids are present in meadow fescue containing the endophyte (Neotyphodium uncinatum Gams, Petrini and Schmidt) (Clavicipitacae). Root, crown and shoot loline alkaloid concentrations in 10 selected lines from meadow fescue ecotypes are reported for the first time, from a Canterbury farm during 2004–05. The concentrations of four loline alkaloid derivatives, N-formyl loline (NFL), N-acetyl loline (NAL), N-acetyl norloline (NANL) and N-methyl loline (NML), in these lines (each line represented by one genotype) were determined at four harvest dates during late spring, late summer, and early and late autumn. There were marked differences in loline alkaloid concentration between lines and seasons. Maximum shoot loline concentration was recorded in summer (up to 2860 µg/g in Fp408). Root loline alkaloid concentration was substantially higher in late autumn (up to 790 µg/g in Fp408) and the shoot concentration correspondingly lower than in spring, summer and early autumn suggesting loline alkaloid transportation from shoots to roots. In the lines tested at each of the four harvest dates in spring, summer, and autumn, the root, crown, and shoot alkaloid concentration with minor exceptions was NFL > NAL > NANL > NML.

Effects of loline-producing endophyte-infected meadow fescue ecotypes on New Zealand grass grub (Costelytra zealandica)

Loline alkaloids produced by endophyte-infected meadow fescue were high (>1000 µg/g) in roots. The larvae of New Zealand grass grub are major subterranean pasture pests. In laboratory and field studies, grass grub larvae feeding on roots of endophyte-infected meadow fescue containing lolines at concentrations >450 µg/g either lost weight or gained less weight than the corresponding controls feeding on endophyte-free or low-loline meadow fescue. These results demonstrate that loline alkaloids in roots of meadow fescue have the potential to deter grass grub larvae from feeding and could contribute to control of this pest in a sustainable manner.

Seasonal changes in leaf and stem loline alkaloids in meadow fescue

Leaf and stem loline alkaloid concentration in 10 European meadow fescue (Festuca pratensis Huds.) lines grown in a field in Canterbury, New Zealand, were determined in samples collected six times between early spring 2004 and late autumn 2005. Significant differences in loline alkaloid concentrations were noted between lines and between harvest times. Higher total loline alkaloid concentrations (up to 4990 µg g–1) were found in stems compared to leaf (up to 1770 µg g–1). However, the seasonal accumulation pattern of different loline alkaloid concentrations in leaf and stem varied. In most lines, stem loline concentration peaked sharply in late spring and declined during early summer and autumn. The seasonal pattern of leaf loline alkaloid concentration followed the stem concentration except for a sharp decline in early summer followed by an increase in late summer. In most instances, the concentration of N-formyl loline was the highest > N-acetyl loline > N-acetyl norloline > N-methyl loline. The possible role of stem and leaf loline alkaloids to deter pasture-feeding insects is briefly discussed.

Complex Interactions among Sheep, Insects, Grass, and Fungi in a Simple New Zealand Grazing System

Epichloë fungi (Ascomycota) live within aboveground tissues of grasses and can have important implications for natural and managed ecosystems through production of alkaloids. Nonetheless, vertebrate herbivores may possess traits, like oral secretions, that mitigate effects of alkaloids. We tested if sheep saliva mitigates effects of Epichloë alkaloids on a beetle pest of perennial ryegrass (Lolium perenne L.) in a New Zealand pasture setting. Plants with one of several fungal isolates were clipped with scissors, grazed by sheep, or clipped with sheep saliva applied to cut ends of stems. We then assessed feeding damage by Argentine stem weevils on blade segments collected from experimental plants. We found that clipping plants induced synthesis of an alkaloid that reduces feeding by beetles and that sheep saliva mitigates this effect. Unexpectedly, the alkaloid (perloline) that explains variation in beetle feeding is one produced not by the endophyte, but rather by the plant. Yet, these effects depended upon fungal isolate. Such indirect, complex interactions may be much more common in both managed and natural grassland systems than typically thought and could have implications for managing grazing systems.