Response to selection for grazing tolerance in winter-active populations of phalaris (Phalaris aquatica L.). 2. Correlated response in yield potential, plant characteristics, and alkaloid levels
R. A. Culvenor A E , S. P. Boschma B and K. F. M. Reed C DA CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
B NSW Department of Primary Industries, Tamworth Agricultural Institute, 4 Marsden Park Rd, Calala, NSW 2340, Australia.
C Department of Primary Industries Victoria, Mt Napier Road, Hamilton, Vic. 3300, Australia.
D Present address: Reed Pasture Science, 430 Beveridge Road, Hamilton, Vic. 3300, Australia.
E Corresponding author. Email: richard.culvenor@csiro.au
Crop and Pasture Science 60(11) 1107-1116 https://doi.org/10.1071/CP09037
Submitted: 28 January 2009 Accepted: 27 July 2009 Published: 19 October 2009
Abstract
Phenotypic changes in populations of perennial grasses are known to occur in response to natural or deliberate selection under grazing. These changes may have agronomic significance. Associated changes in morphology and yield potential of young stands in response to 2 cycles of selection for grazing tolerance were examined in 3 winter-active breeding populations of the perennial grass, phalaris (Phalaris aquatica L.). Levels of alkaloids which potentially could affect palatability were also examined. There was a decline in seedling growth and autumn and winter yield in spaced plants of 6.3–7.5% per cycle pooled across populations. Seedling growth measured in sown swards at 2 sites was not affected by selection. Visually estimated sward yield in the second year, ignoring large gaps, agreed with the spaced plant results but the decline was not significant at P ≤ 0.05 when herbage yield was measured by mowing, probably due to effects of plant density. On balance, it was concluded that a decline in individual plant yield of 6–7% per cycle had occurred but this could be compensated by higher density, particularly over time as differences in persistence under grazing developed. The most pronounced morphological response to selection under grazing was towards a more densely tillered growth habit, although one exception occurred. There was also a tendency towards a more prostrate growth habit and later heading, but this was significant only for the most erect and earliest maturing population. Two cycles of selection did not significantly affect summer activity or area of plant base in any population. Tryptamine alkaloids were below the level likely to affect palatability but tended to increase with selection, particularly in a very low tryptamine base population, which suggested that they may play a role in persistence.
Because of potentially deleterious effects on yield, care is required in using this selection method. A balance of yield potential and grazing tolerance appropriate to the management system is needed.
Additional keywords: palatability, perennial grass, persistence.
Acknowledgments
We thank Mr G. Wake, ‘Wakefield Park’, Bulart, and Mr R. Veness, Rye Park, for kindly allowing us to conduct the experiments on their land. Technical assistance by Scott McDonald and Phillip Veness (CSIRO), Terry Mullens (NSW Department of Primary Industries, Tamworth), and Darren Picket and Harry Armstrong (Department of Primary Industries, Hamilton, Victoria) is gratefully acknowledged. We also thank Melissa Sprague (Department of Primary Industries, Hamilton, Victoria) for collecting and extracting herbage samples at the Bulart site for alkaloid analysis. Support for this project was provided by Australian woolgrowers and the Australian government through Australian Wool Innovation Ltd.
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