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National white clover improvement - support research

R.D. FitzGerald and J.F. Ayres

NSW Agriculture, Agricultural Research and Advisory Station, Glen Innes NSW 2370

White clover cultivars in use in Australia have serious limitations; unreliable presence and yield, poor persistence through periods of summer moisture stress, sensitivity to grazing pressure and grass competition, and low winter activity (1). Research supporting the National White Clover Improvement Programme (NWCIP) is directed at determining characteristics of white clover that address these problems and promote successful performance in grazed pasture.

Methods

Four current projects are determining useful characteristics for selection.

Cultivar evaluation studies [20 cultivars, grazed plots] are testing prominent cultivars, prerelease lines and ecotypes from Australia, New Zealand, the United Kingdom and USA to identify adapted types.

Summer survival studies [cultivars x watering regimes x defoliation] are examining cultivars with contrasting stolon and floral characteristics under a range of moisture regimes to determine plant traits that confer tolerance to summer moisture deficits.

Multi-line sward studies [cultivars x companion grass x grazing defoliation] are evaluating cultivars with diversity in characters influencing persistence and production to determine their significance under competition from a companion grass and a range of defoliation pressures.

Genotypic variation analysis [genotypes, pot culture] is estimating genetic variation in shoot, root and quality characteristics to determine the potential for genetic manipulation.

Results and discussion

Cultivar differences are evident for seasonal yield, stolon development, seedling recruitment and diet preference rating. In early growth cycles yield of cultivars ranged from 80-220 kg/ha (winter), 320-1410 kg/ha (spring), 3-430 kg/ha (summer) and 2-90 kg/ha (autumn). The results highlight the significance of perenniality for agronomic performance. Summer survival studies are directed at enhancement of perenniality through determination of morphological features that improve the ability of white clover to survive moisture stress. Early results suggest that improved survival under a deficit of moisture may be associated with higher root node density, and that for tap-rooted types, changes in plant root morphology as the clover plant matures influence the response to moisture stress.

Acknowledgements

Support research for the National White Clover Improvement Programme is funded by the Wool Research and Development Corporation.

References

1. Archer, K.A. and Robinson, G.G. 1989. Aust. J. Agric. Res. 40, 605-616.

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