1. Priscila Freitas
Bio-Protection Research Centre
Lincoln University
Lincoln, New Zealand
Author photo
Phil Rolston2, Stuart Card3, Travis Glare1 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
The influence of temperature on the vertical transmission of a mutualistic tall fescue endophyte
Introduction
Many Poaceae grasses form a symbiosis with Epichloë endophytes and some cause toxicity to livestock. Endophytes with no livestock toxicosis but still possessing advantageous traits of insect deterrent alkaloids have been discovered. Selection and transfer of these endophytes into elite grass cultivars has resulted in pastures with improved persistence with no, or reduced, livestock toxicosis. These novel associations are now successfully marketed in Australia, Argentina, Brazil, Chile, New Zealand, Uruguay and the USA. 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 and crop management regimes.
Objective
To determine the influence of temperature on the vertical transmission of a tall fescue (Festuca arundinacea) endophyte, Epichloë FaTG-3 strain AR501 in its original host compared to that in a novel host, perennial ryegrass (Lolium perenne).
Materials and Methods
Two endophyte-grass associations were studied: (i) Epichloë FaTG-3 strain AR501 within its original host (tall fescue); (ii) AR501 in an artificial association of perennial ryegrass. Newly emerged seedlings of both associations were arranged in a controlled environment at four temperature regimes ranging from 6-25°C (Figure 4). After 3 weeks, endophyte transmission frequencies were determined (Figure 1). Plants from both associations were then transferred from 12/6°C to 25/16°C and vice versa (Figure 2) and their endophyte biomass quantified after 6 weeks (Figure 3).
Tissue print- immunoblot for endophyte frequency detection
ELISA
Endophyte biomass
concentration detection
8 trays
Tissue print- immunoblot for endophyte frequency detection
Figure 3: Endophyte biomass concentration detection in selected plants after 6 weeks.
Figure 1: Endophyte transmission frequency detection in selected plants after 3 weeks.
12/6°C Growth chamber
25/16°C Growth chamber
Figure 2: Plants from both associations were transferred across chambers after 3 weeks.
Results
For perennial ryegrass the endophyte transmission frequency 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 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).
Table 1. Effect of temperature regimes on endophyte transmission frequency (%) of perennial ryegrass and tall fescue plants containing the endophyte strain AR501 at the week three harvest.
Temperature regime (day/night)
Endophyte transmission frequency (%) in perennial ryegrass
Endophyte transmission frequency (%) in tall fescue
12/6°C
83.3
100
25/16°C
33.3
Significant effects * NS
Figure 4. Endophyte concentration (mg/g) at week six harvest in perennial ryegrass (PR) and tall fescue (TF) plants. Vertical bar indicates the value for Fisher’s LSD.
NS=Not Significant; *=P<0.05
Conclusion
Temperature was a significant factor in the transmission of this novel grass-endophyte association and this should be taken into account during future research.
Acknowledgements
Dr Lyn Briggs - Forage Improvement, AgResearch Ltd.
Dave Saville - Saville Statistical Consulting Ltd.
Grasslanz Technology Ltd.