1. Phil Rolston2, Lyn Briggs2 , Stuart Card2, Travis Glare1 , David Hume2 and John Hampton1
1 Bio-Protection Research Centre, Lincoln University, Christchurch, New Zealand
2 Forage Improvement, AgResearch Ltd., Lincoln Research Centre, Christchurch, New Zealand
3 Forage Improvement, AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
Priscila Freitas
Bio-Protection Research Centre
Lincoln University
Lincoln, New Zealand
Author photo
Transmission frequency and concentration of loline alkaloids in novel tall fescue endophyte associations under the influence of temperature
Results
For perennial ryegrass the endophyte transmission frequency of AR501 was significantly higher in plants kept at a cold (day/night 12/6°C) temperature regime compared to the warm (day/night 25/16°C) regime. This was not observed in tall fescue (Table 1). The endophyte biomass and loline concentrations of both associations increased significantly when plants were transferred from the cold to warm temperature regime but not from the warm to cold temperature regime (Figure 4 and 5).
Introduction
Cool-season grasses frequently form mutualistic symbioses with Epichloë fungal endophytes (Figure 1) and some cause toxicity to livestock. Endophytes with no livestock toxicosis but still possessing advantageous traits of insect deterrent alkaloids have been discovered. Artificial associations have been developed by selecting and transferring agriculturally beneficial Epichloë strains to elite grass cultivars. Epichloë species exhibit strong host specificity and the asexual form is exclusively vertically transmitted through maternal lines via the seed embryo. This process is far from perfect, with endophyte transmission failures attributed to factors including endophyte and host genotypes, environmental factors including temperature, and crop management regimes.
Table 1. Effect of temperature regimes in endophyte transmission frequency (%) of perennial ryegrass and tall fescue plants infected with Epichloë endophyte strain AR501 at the week three harvest.
Temperature regime (day/night)
Endophyte transmission frequency (%) in perennial ryegrass
Endophyte transmission frequency (%) in tall fescue
12/6C°
83.3
100
25/16C°
33.3
Significant effects * NS A B
Figure 1: Epichloë fungal endophyte. A, Epichloë strain AR501 culture. B, endophyte hyphae between leaf cells.
Objective
To determine whether temperature affects on AR501 transmission, fungal biomass and concentrations of loline alkaloids, in both tall fescue and perennial ryegrass hosts.
Materials and Methods
Two endophyte-grass associations were studied: (i) Epichloë strain AR501 within its original host (tall fescue); (ii) AR501 in an artificial association with perennial ryegrass. Newly emerged seedlings of both associations were arranged in a controlled environment at four temperature regimes ranging from 6 to 25°C (Figure 4 and 5). Plants from both associations were transferred from 12/6°C to 25/16°C and vice versa (Figure 2) and their endophyte frequency, biomass and loline concentration quantified after 6 weeks. Endophyte frequency was assessed using Tissue print- immunoblot, biomass and loline concentration were assessed using ELISA.
Figure 4. Endophyte biomass (mg/g) at week six harvest in perennial ryegrass (PR) and tall fescue (TF) plants. Vertical bar indicates the value for Fisher’s LSD at P<0.05.
12/6°C Growth chamber
25/16°C Growth chamber
Figure 5. Loline concentration (µg/g) at week six harvest in perennial ryegrass (PR) and tall fescue (TF) plants. Vertical bar indicates the value for Fisher’s LSD at P<0.05.
Conclusion
Temperature was a significant factor in the endophyte biomass and loline concentration in both species and on transmission of AR501 in perennial ryegrass. This should be taken into account during future research.
Figure 2: Transference of plants from both associations between chambers after 3 weeks.
Acknowledgements
Dave Saville - Saville Statistical Consulting Ltd.
Grasslanz Technology Ltd.