AbstractFusarium circinatum is an economically important pathogen of Pinus species, which also occurs on Douglas fir (Pseudotsuga menzeisii). It causes pitch canker of mature trees and root and collar rot of seedlings and cuttings. In 2007, pitch canker was observed on Pinus radiata in the Western Cape and this was the first outbreak of this disease in South Africa. The Cape flora in this area includes native coniferous species of Podocarpus and Widdringtonia. In this study, seedlings of P. latifolia, P. elongatus, P. henkelii, W. schwartzii, W. cederbergensis and W. nodiflora were inoculated with a virulent isolate of F. circinatum, to assess their susceptibility. Six weeks after inoculation, there was no lesion development in any of the species inoculated. Pinus patula seedlings used as a positive control were severely affected. Results of this study show that species of Podocarpus and Widdringtonia, native to the Western Cape, are not threatened by the pitch canker fungus

Coutinho, T.A.

Porter, B.

Wingfield, M.J.

Fusarium circinatum is an economically important pathogen of Pinus species, which also occurs on Douglas fir (Pseudotsuga menzeisii). It causes pitch canker of mature trees and root and collar rot of seedlings and cuttings. In 2007, pitch canker was observed on Pinus radiata in the Western Cape and this was the first outbreak of this disease in South Africa. The Cape flora in this area includes native coniferous species of Podocarpus and Widdringtonia. In this study, seedlings of P. latifolia, P. elongatus, P. henkelii, W. schwartzii, W. cederbergensis and W. nodiflora were inoculated with a virulent isolate of F. circinatum, to assess their susceptibility. Six weeks after inoculation, there was no lesion development in any of the species inoculated. Pinus patula seedlings used as a positive control were severely affected. Results of this study show that species of Podocarpus and Widdringtonia, native to the Western Cape, are not threatened by the pitch canker fungus

Wingfield, Michael J.

Coutinho, Teresa A.

UPSpace at the University of Pretoria

South African Journal of Botany

Susceptibility of South African native conifers to the pitch canker pathogen, Fusarium circinatum

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Susceptibility of South African native conifers to the pitch canker pathogen, Fusarium circinatum 

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South African Journal of Botany 75 (2009) 380–382
www.elsevier.com/locate/sajbResearch Note
Susceptibility of South African native conifers to the pitch canker pathogen,
Fusarium circinatum
B. Porter, M.J. Wingfield, T.A. Coutinho ⁎
Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa
Received 19 August 2008; received in revised form 6 November 2008; accepted 11 November 2008Abstract
Fusarium circinatum is an economically important pathogen of Pinus species, which also occurs on Douglas fir (Pseudotsuga menzeisii). It
causes pitch canker of mature trees and root and collar rot of seedlings and cuttings. In 2007, pitch canker was observed on Pinus radiata in the
Western Cape and this was the first outbreak of this disease in South Africa. The Cape flora in this area includes native coniferous species of
Podocarpus and Widdringtonia. In this study, seedlings of P. latifolia, P. elongatus, P. henkelii, W. schwartzii, W. cederbergensis and
W. nodiflora were inoculated with a virulent isolate of F. circinatum, to assess their susceptibility. Six weeks after inoculation, there was no lesion
development in any of the species inoculated. Pinus patula seedlings used as a positive control were severely affected. Results of this study show
that species of Podocarpus and Widdringtonia, native to the Western Cape, are not threatened by the pitch canker fungus.
© 2008 SAAB. Published by Elsevier B.V. All rights reserved.Keywords: Conifer; Fusarium circinatum; Pitch canker; Podocarpus; WiddringtoniaFusarium circinatum (Nirenberg and O'Donnell) is a
pathogen which has a serious economic impact on pine
production in South Africa (Wingfield et al., 2002). The
South African forestry industry contributes significantly to the
economy through the production of solid timber and pulp
products (Anonymous, 2005), and is based on exotic plantations
of pines and eucalypts. The Pinus species most extensively
planted are Pinus patula (Schl. et Cham.) and P. elliottii
(Chapm.). P. radiata (D. Don.) is only grown in the Western
Cape.
Fusarium circinatum was first reported from a pine
production nursery in Mpumalanga (Viljoen and Wingfield,
1994) and is now endemic in nurseries throughout the country,
where it causes root and collar rot of both seedlings and
cuttings. In 2007, large, resinous cankers appeared on mature
P. radiata trees in the Western Cape and this was the first report
of pitch canker in South Africa (Coutinho et al., 2007). These
plantations are situated in close proximity to the unique Cape
flora, which includes native conifers such as Podocarpus and⁎ Corresponding author.
E-mail address: teresa.coutinho@fabi.up.ac.za (T.A. Coutinho).
0254-6299/$ - see front matter © 2008 SAAB. Published by Elsevier B.V. All righ
doi:10.1016/j.sajb.2008.11.003Widdringtonia. Because F. circinatum is an exotic pathogen in
South Africa, is known to infect numerous Pinus species in
America and Europe (Storer et al., 1997; Hodge and Dvorak,
2000; Enebak and Stanosz, 2003), and can cause disease on a
non-pine species, Pseudotsuga menziesii (Mirb.) (Douglas-fir)
(Gordon et al., 2006), concern has been raised that it might
threaten native conifers.
Inoculation trials with 20 seedlings each of Podocarpus
latifolia [(Thunb.) R.Br.: Mirb.], P. elongatus [(Ait.) L'Herit.:
Pers.], P. henkelii (Stapf. Ex Dallim. & Jacks.), Widdringtonia
schwartzii (Endl.), W. cederbergensis (Marsh) and W. nodiflora
[(L.) Powrie], were conducted using a known virulent strain of
F. circinatum (FCC 3579). Inoculum was produced by culturing
this isolate on half strength potato dextrose agar (20 g Potato
dextrose agar powder [Merck, Biolab Diagnostics (Pty) Ltd.],
5 g Agarose bacteriological powder [Merck, Biolab Diagnostics
(Pty) Ltd.], 1 l distilled water) for 15 days. Spores were washed
from the cultures with 15% glycerol, excess mycelium was
filtered through sterile cheese cloth, and the concentration
adjusted to 5×104 spores/ml using a haemocytometer. The
seedlings were wounded by needle puncture of the main stem
[Promex hypodermic syringe needles, 21 G, 0.80×40 mm], andts reserved.
Fig. 1. A. Podocarpus henkelii 12 weeks after inoculation, arrows denote inoculation points. Seedling ‘1’ negative control, ‘2’ and ‘3’ inoculated with Fusarium
circinatum. B. Widdringtonia nodiflora seedlings 12 weeks after inoculation, arrows denote inoculation points. Seedling ‘1’ negative control, ‘2’ inoculated with
Fusarium circinatum. C. Local discolouration around inoculation point on Podocarpus latifolia seedling (arrow denotes inoculation point). D. Positive controls,
P. patula seedlings 3 weeks after inoculation. Bark has been removed to expose lesion development. All P. patula seedlings dead at 12 weeks.
381B. Porter et al. / South African Journal of Botany 75 (2009) 380–382inoculated with a 10 μl drop of spore suspension. This
technique was similar to that used by Kuhlman (1987), McCain
et al. (1987) and Blakeslee and Rockwood (1999). Podocarpus
seedlings were purchased from indigenous tree nurseries and
Widdringtonia seedlings were grown from seed purchased
from the Kirstenbosch Botanical Gardens (www.sanbi.org/
frames/kirstfram.htm). Ten seedlings of each species were
inoculated with sterile 15% glycerol as a negative control, and
20 Pinus patula seedlings were inoculated as a positive control.
At the time of inoculation, all plants were 10 months old,
planted in 2.5l black plastic bags containing composted bark
medium, and maintained at a constant temperature of 25 °C in a
greenhouse. Seedlings were evaluated for disease development
at 3, 6 and 12 weeks after inoculation. The experiment was
repeated once.
None of the conifers inoculated showed lesion development
(Fig. 1-A, B), although some seedlings developed minor
callusing and discolouration localized to the bark above the
inoculation point (Fig. 1-C). All P. patula seedlings had distinct
lesion development at 3 weeks after inoculation (Fig. 1-D), and
by 12 weeks all had died. Thus far all plant species, other than
Pinus spp. and P. menziesii, that have been tested for
susceptibility to F. circinatum have been found to be highly
resistant (McCain et al., 1987; Dick and Simpson, 2004). The
resistance of Podocarpus and Widdringtonia spp. shown in this
study is reassuring as W. cederbergensis is under threat fromover-exploitation and fire (Manders, 1986). W. cederbergensis
exists as small scattered populations in rocky outcrops of the
Cederberg, and in some localities is incapable of maintaining
the wild population (Manders and Botha, 1989). An additional
threat by an aggressive, exotic pathogen could be detrimental.
Acknowledgements
We thank the Forestry and Agricultural Biotechnology
Institute (FABI), the Centre for Tree Health Biotechnology
(CTHB), the Tree Protection Co-operative Program (TPCP),
and the National Research Foundation (NRF), for funding.
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Susceptibility of South African native conifers to the pitch canker pathogen, Fusarium circinatum

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