Key points

• Inoculating wheat with strains of Epichloë fungi has been shown to reduce damage by the Argentine stem weevil and wheat sheath miner
• Agronomic trials with endophytic rye have shown increases in grain yield of up to 25 per cent under some treatments and indicate that increases of about 20 per cent may be realised for wheat

New Zealand researchers are translating their successes with endophytes in pasture species to wheat in expectation that the mutually beneficial relationship could improve wheat resilience in the face of pests and climatic pressures.

The work is being done with investment from GRDC, Grasslanz Technology, the Foundation for Arable Research and the New Zealand Government.

Temperate grasses (ryegrass and tall fescue) have been inoculated with Epichloë fungal endophytes to improve yield and persistence through providing ‘natural’ protection against pest, diseases and drought. In fact, selected Epichloë endophytes have been so effective within the pasture grass industry that they are now a standard ingredient for high-performing pastures.

The aim of this research is to identify Epichloë isolates taken from wild relatives of cereals, then inoculate strains of this endophyte, with appropriate beneficial properties, into elite cereal genotypes.

This process leads to functional associations between elite cereal cultivars (wheat and rye) and endophytic Epichloë fungi, to protect cereals from pre and post-harvest invertebrate pest attack and potentially enhance their tolerance to abiotic stresses.

The endophyte produces bioactive molecules providing these beneficial effects; these are being tested to ensure they are not harmful to humans or livestock and will not impair the nutritive or health characteristics of cereal forage or grain.

Findings

Many Epichloë isolates from grasses in the genera Hordeum (of which barley is a member) and Elymus (of which wheatgrass and wild rye are members) have been assembled from worldwide collections and characterised. These have been found to have an extensive range of secondary metabolites which have known bioactivity against a range of pests and disease.

Inoculation of Epichloë endophyte into rye (Secale cereale) has been successful, with good transmission rates through seed. Endophyte bioactivity against insect pests in endophyte strain AR3002-inoculated rye resulted in lower levels of damage from Argentine stem weevils (Listronotus bonariensis), wheat sheath miners (Cerodontha australis) and thrips (Frankliniella spp.) than in endophyte-free rye.

A small grain storage trial has shown some suppression in the total number of saw-toothed grain beetles (Oryzaephilus surinamensis) after three months. Wheat seed has been generated from plants that were infected with the same endophyte strain, identified as the first non-toxic endophyte to give a normal plant phenotype.

A collaboration at the University of Adelaide has seen four endophyte strains inoculated into 20 selected experimental substitution/addition wheat lines (supplied by Tottori University, Japan). The next step will be to examine these wheat lines for effective endophyte transmission and bioactivity and then cross with modern wheats.

Industry impacts

AR3002-inoculated wheat seed has been tested in mouse feeding trials. So far there is no evidence of any toxicity or animal health issues associated with this Epichloë endophyte strain in the grain. Similarly, ruminants have safely grazed or consumed forage, silage or grain of rye inoculated with AR3002 endophytes.

While agronomic trials with endophytic wheat are still to be undertaken, agronomic trials with endophytic rye have shown increases in grain yield of up to 25 per cent under some treatments. A similar result for endophytic wheats would raise the average grain yield by 20 per cent.

More information: John Caradus,  +64 6 351 8001, +64 293 518 001,  john.caradus@grasslanz.com