|Authors: ||S.L. von Broembsen, G.J. Brits| Phytophthora root
rot is a limiting factor in the production of cut flower
pincushions worldwide, but especially in South Africa.
Investigations were initiated to identify root rot resistance
within the genus Leucospermum that might be utilized for the
development of resistant cultivars or rootstocks. Three
different methods were used to assess the resistance of
Leucospermum hybrids and species selections. Firstly, shoot
cuttings were wound inoculated with P. cinnamomi mycelium under
controlled, laboratory conditions. Lengths of lesions which
developed from the inoculations were used to estimate relative
resistance. This detached shoot assay proved too unreliable to
be used for assessment. Secondly, one-year-old rooted cuttings
were inoculated by applying zoospores of Phytophthora cinnamomi
to the soil mix of individual pots in a trial conducted in a
shade house. All of the lines tested were found to be
susceptible to infection, but some lines were tolerant to infec