Abstract:
The genus Phytophthora contains many destructive and globally important plant pathogens. In the last decade,
targeted sampling efforts have resulted in a dramatic increase in the number of known species, as well as a better understanding
of their global distribution. Routine activities undertaken in botanical gardens, combined with great numbers of local and
international visitors, place botanical gardens at risk to the accidental introduction and establishment of pathogens such as
Phytophthora spp. In this study, the occurrence of Phytophthora was investigated in two botanical gardens in the KwaZulu-
Natal Province of South Africa. Symptomatic collar and stem tissues were collected, and root and rhizosphere soil samples
were taken from trees exhibiting symptoms of decline. Standard baiting techniques and direct plating of symptomatic
tissues revealed the presence of seven species of Phytophthora residing in four phylogenetic clades. Five of these species, P.
cinnamomi, P. citrophthora, P. multivora, P. parvispora and the informally designated taxon Phytophthora sp. stellaris were
known to be present in South Africa and P. aquimorbida was recorded for the first time. Of these, P. citrophthora represented
a novel host-pathogen association causing bleeding cankers on indigenous Celtis africana. A multilocus phylogenetic analysis
based on ITS, βtub, cox1 and hsp90 sequences showed the presence of an undescribed species belonging to the Phytophthora
ITS Clade 5. This species is described here as Phytophthora mammiformis sp. nov. This study highlights the importance of
monitoring botanical gardens for the detection and discovery of pathogens and emphasises their value as sites for the
discovery of novel host-pathogen associations.
Description:
SUPPLEMENTARY MATERIAL : FIG. S1: Maximum likelihood phylogeny using the single gene
(ITS, βtub, cox1 and hsp90) datasets for ITS Clade 5 Phytophthora
species. The clades of Phytophthora mammiformis are
highlighted with a coloured block. Phytophthora podocarpi
NZFS 3642 was used as an outgroup. Numbers on the branches
are bootstrap support values values (n = 1 000, only ≥ 70 %
displayed)/posterior probabilities (only ≥ 0.8). Superscript T
denotes material with a type status.
TABLE S1. GenBank accession numbers of Phytophthora isolates
obtained from two botanical gardens in the KwaZulu-Natal
Province of South Africa and status in South Africa.