19 January 2009
In New Zealand many common pasture plants are attacked by insects, damaging the plants themselves and causing economic losses.
In response to these attacks plants produce a number of natural compounds in an effort to ward off predators; however, some of these compounds are toxic to the animals eating the plants, and may cause illness and death.
The grasses do not produce the toxic compounds themselves; instead, they are produced by a type of fungus called an endophyte that is intimately associated with the grass (in what is called a symbiotic relationship that benefits both the fungi and the grass). These natural compounds, called alkaloids, produced by the endophyte, protect the plant from insect attack.
Dr Brian Patchett from the Agriculture and Life Sciences Division at Lincoln University has undertaken research on the effect of particular alkaloids, known as lolines that are produced in meadow fescue grass containing the endophyte Neotyphodium uncinatum, on sheep, grass grubs and the Argentine stem weevil.
“The main objective of my research was to investigate the concentration and distribution of loline alkaloids in 12 Cropmark Seeds meadow fescue breeding lines and the effects of these loline alkaloids on two common pasture insects in New Zealand, grass grub and Argentine stem weevil,” said Dr Patchett.
“These breeding lines were previously assessed by Cropmark Seed as having loline production but no detectable ergovaline or lolitrem B content. Ergovaline and lolitrem B alkaloids are known to be harmful to sheep.”
Loline alkaloids are commonly found in the endophyte-infected grasses tall fescue and meadow fescue. In meadow fescue lolines are often found in the absence of other alkaloids.
“My work showed that loline alkaloids produced by different parts of meadow fescue grass (leaves, stems, roots) containing the endophyte Neotyphodium uncinatum, were non toxic to sheep but toxic to the two important pasture insect pests, grass grub and Argentine stem weevil.”
In short term laboratory and field studies, grass grub larvae feeding on roots of endophyte infected meadow fescue containing lolines either lost weight or gained less weight than the corresponding controls feeding on endophyte free or grass lines with low loline concentration.
In similar studies the Argentine stem weevil also exhibited a reduction in feeding with fewer feeding holes in meadow fescue leaves in the presence of lolines compared with the absence of lolines.
These findings are significant in terms of developing an environmentally friendly and sustainable biological approach to the control of insect pests and related potential benefits to improving livestock performance in New Zealand.
“The reason why I studied meadow fescue rather than the more commonly grown tall fescue is that the endophyte associated with meadow fescue often only produces lolines while tall fescue generally has several different alkaloids associated with it,” said Dr Patchett.
A condition called ryegrass staggers is also caused by a toxin produced by an endophtye associated with another grass, perennial ryegrass.
The principle of incorporating useful endophytes into grass varieties using traditional techniques has been used by plant breeders at Cropmark Seed for the last 10 years. Dr Patchett’s research opens up new horizons in the particular area for loline endophytes.