|dc.description.abstract||The problems associated with the use of white clover in pastures
in the eastern high potential areas of South Africa i.e. high P
requirements, low tolerance to high Al levels and low pH in the
soil as well as a limited survival time of approximately 30
months, were identified and found to be related to the inadequate
root system of white clover cultivars.
During the improvement programme cultivars available on the world
market were introduced and evaluated under dryland conditions.
Selections were made from these introductions on the basis of
root conformation in high AI, low pH soils, their response to
grazing and induced moisture stress.
A laboratory technique for the improvement of Al tolerance was
developed and the tolerance of white clover plants to high levels
of Al was improved but due to the complexity of pasture plant
improvement it was decided that the selection for tolerance to Al
could be more effectively carried out in the field. The effectiveness of vesicular arbuscular mycorrhizas as
phosphate gatherers indicated that local strains of mycorrhizas
combined as effectively with white clover as the imported
As no seed production of white clover is undertaken in South
Africa guidelines for local seed production were also
As a result of the improvement programme, Trifolium repens cv.
DUSI was developed as an open pollinated synthetic variety, based
on thirty eight selected mother lines. DUSI has a greater
tolerance to high AI, low pH, low P in the soil and due to an
improved root system with a high percentage of secondary taproots
produces better under dryland conditions and has a longer stand
life than any of the cultivars of white clover available on the
Plant Breeders Rights were obtained for cv. DUSI and the cultivar
was inscribed on the South African variety list. Limited amounts
of Breeders seed have been made available to the South African
Forage Seed Association for commercial seed production.||en