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| Plant Pathology
(2007) 56
, 624–636 Doi: 10.1111/j.1365-3059.2007.01608.x
© 2007 The Authors 624
Journal compilation © 2007 BSPP
Blackwell Publishing Ltd Botryosphaeriaceae occurring on native Syzygium cordatum
in South Africa and their potential threat to Eucalyptus
D. Pavlic a
*, B. Slippers
b , T. A. Coutinho
a
and M. J. Wingfield
a a
Department of Microbiology and Plant Pathology; and
b Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, 0002, South Africa
Eight species of the Botryosphaeriaceae (canker and dieback pathogens) were identified on native Syzygium cordatum
in South Africa, based on anamorph morphology, ITS rDNA sequence data and PCR-RFLP analysis. The species identified were Neofusicoccum parvum, N. ribis, N. luteum, N. australe, N. mangiferae
, Botryosphaeria dothidea, Lasiodiplodia gonubiensis
and L. theobromae
. Their pathogenicity on S. cordatum
seedlings and a Eucalyptus grandis
×
camaldulensis
clone was determined in glasshouse inoculation trials. Isolates of all identified species, except one of N. mangiferae
Eucalyptus
clone than on S. cordatum
. Some of the species that cross-infected these hosts, such as N. ribis, N. parvum
and L. theobromae
, were amongst the most pathogenic on the Eucalyptus
clone, while B. dothidea
and L. gonubiensis
were the least pathogenic. Results of this study illustrate that species of the Botryosphaeriaceae from native hosts could pose a threat to introduced Eucalyptus
spp., and vice versa
. Keywords
: Botryosphaeriaceae, Eucalyptus
spp., host association, indigenous tree, latent pathogen, Myrtaceae
Introduction
The Botryosphaeriaceae (Dothideales) is comprised of fungal species that have a wide geographic distribution and extensive host range, including Eucalyptus
spp. (Myrtaceae) (von Arx & Müller, 1954; Crous et al
., 2006). These fungi are latent and opportunistic pathogens that occur as endophytes in symptomless plant tissues and they can cause rapid disease development when plants are exposed to unsuitable environmental conditions such as drought, freezing, hot or cold winds, hail wounds or damage caused by insects or other pathogens (Fisher et al
., 1993; Smith et al
., 1996). Species of the Botry- osphaeriaceae cause a wide variety of symptoms on all parts of Eucalyptus
trees and on trees of all ages, but are mostly associated with cankers and dieback followed by extensive production of kino, a dark-red tree sap, and in severe cases mortality of trees (Smith
., 1994, 1996; Old & Davison, 2000). The Myrtaceae is a predominantly southern hemi- sphere angiosperm family that accommodates more than 3000 species, largely distributed in the tropical and temperate regions of Australasia, as well as Central and South America (Johnson & Briggs, 1981). Species of the Myrtaceae also form an integral part of the Southern African indigenous flora (Palgrave, 1977). In this context, the most widespread myrtaceous tree in South Africa is
(Palgrave, 1977). Eucalyptus
species, native Australasian Myrtaceae, are the most widely grown trees in commercial forestry plantations, particularly in the tropics and southern hemisphere, including South Africa. Movement of pathogens between native and intro- duced hosts has been recognized as a significant threat to plant communities (Slippers et al
., 2005). Because of the potential threat of native pathogens to non-native Eucalyptus
plantations, various recent studies considered fungal pathogens on native hosts in areas where Eucalyptus
spp. are intensively planted (Wingfield, 2003; Burgess et al
., 2006). These studies showed that pathogens which can cause severe diseases on Eucalyptus
spp. also occur on native plants and thus pose a threat to Eucalyptus
spp. Where plantations of non-native Eucalyptus
spp .
are established amongst closely related native myrtaceous trees, pathogens could cross-infect either the native or introduced host group and cause serious diseases (Burgess & Wingfield, 2001). For example, the rust fungus Puccinia psidii
, which occurs on a variety of native Myrtaceae in South America, has become one of the main pathogens on exotic
Eucalyptus
spp. in that area (Coutinho et al
., 1998). In South Africa, species of the Botryosphaeriaceae are amongst the most important canker pathogens in planta- tions of non-native
spp., causing twig dieback, branch and stem cankers and mortality of diseased trees (Smith
et al
., 1994). These fungi have also recently been *E-mail: draginja.pavlic@fabi.up.ac.za Accepted 12 December 2006 Plant Pathology
(2007) 56
, 624–636 Botryosphaeriaceae on Myrtaceae in South Africa
625 PPA_1608
reported as endophytes from native South African trees closely related to Eucalyptus
, such as S. cordatum
and Heteropyxis natalensis
(Smith et al
., 2001). The Eucalyptus
plantations mostly occur in the eastern part of the country where S. cordatum
is widely distributed (Palgrave, 1977; Anonymous, 2002; Fig. 1). Thus, Botryosphaeriaceae that occur on this native tree could pose a threat to exotic Eucalyptus
spp. and vice versa
. However, there have not been any detailed studies on Botryosphaeriaceae on native hosts closely related to Eucalyptus
in South Africa. Because of the economic importance of Eucalyptus
plantations, as well as the need to protect native flora, identification and characterization of Botryosphaeriaceae from
S. cordatum
is of great concern. Recent studies combined morphological characteristics and DNA sequence data to distinguish and identify species within the Botryosphaeriaceae (Denman
., 2000; Zhou & Stanosz, 2001; Crous et al
., 2006). Molecular approaches most commonly used to study Botryosphaeriaceae are comparisons of sequence data from the internal transcribed spacer (ITS) gene region of the rDNA operon (Denman et al
., 2000; Zhou & Stanosz, 2001). However, some closely related or cryptic species of the Botryosphaeriaceae have been difficult to distinguish based on single gene genealogies. Comparisons of sequence data for multiple genes or gene regions were thus used to discriminate between these species (Slippers
., 2004a, c). Furthermore, identification of large numbers of species has been facilitated by PCR restriction fragment length polymorphism (RFLP) techniques (Slippers
., 2004b). The aims of this study were to identify Botryosphaer- iaceae occurring on native S. cordatum
in South Africa, based on ITS rDNA sequence data, PCR-RFLP analysis and anamorph morphology. Isolates belonging to the Botryosphaeriaceae on
and Eucalyptus
were also compared, with special attention given to overlaps and the potential for cross infection. The pathogenicity of the Botryosphaeriaceae isolates from
was furthermore tested on both a Eucalyptus
clone and S. cordatum
in glasshouse trials. Materials and methods Isolates
Isolates used in this study were collected in surveys of Botryosphaeriaceae on native S. cordatum
in different geographical regions of South Africa, in 2001 and 2002 (Table 1, Fig. 1). The 148 isolates that were collected from 11
sites during these surveys form the basis of this study. Between 5 and 45 trees were sampled from each site. From each tree, isolations were made from dying twigs and symptomless, visually healthy twig and leaf tissues. Leaves and twig portions (5 cm in length) were washed in running tap water and surface sterilized by placing them sequentially for 1 min in 96% ethanol, undiluted bleach (3·5–5% available chlorine) and 70% ethanol, then rinsed in sterile water. Treated twig portions were halved and pieces from the pith tissue (2 mm
2 ) and
segments of the leaves (3 mm
2 ) were placed on 2% malt extract agar (MEA; 2% malt extract, 1·5% agar; Biolab) in Petri dishes. Following incubation for 2 weeks at 20
°
C under continuous near-fluorescent light and colonies resembling Botryosphaeriaceae with grey-coloured, fluffy aerial mycelium, were selected. These colonies were trans- ferred to 2% MEA at 25
° C and stored at 5
°
C. All isolates Figure 1 A map of South Africa indicating the area of natural distribution of Syzygium cordatum (left) and sites from where isolates of the Botryosphaeriaceae identified in this study were obtained (stars, right).
Plant Pathology
(2007) 56
, 624 –636
626 D. Pavlic
et al. PP A_1608
Table 1 Isolates considered in the phylogenetic study and pathogenicity trials GenBank ITS
Isolate
a,b Other no.
a
Identity Host
Location Isolator
CMW 7772 Neofusicoccum ribis Ribis
sp. New York, USA B. Slippers & G. Hudler AY236935 CMW 7054
CBS 121 N. ribis
(chromagena) R. rubrum
New York, USA N.E. Stevens AF241177
CMW 14011 N. ribis Syzygium cordatum
Sodwana Bay, S. Africa D. Pavlic DQ316072
CMW 14012 N. ribis S. cordatum
Sodwana Bay, S. Africa D. Pavlic DQ316073
CMW 13990 N. ribis S. cordatum
Sodwana Bay, S. Africa D. Pavlic DQ316074
CMW 13991
CBS 118822 N. ribis S. cordatum
Sodwana Bay, S. Africa D. Pavlic DQ316075
CMW 14016
N. ribis S. cordatum
Kwambonambi, S. Africa D. Pavlic DQ316079
CMW 14031 c N. ribis S. cordatum
Kwambonambi, S. Africa D. Pavlic DQ316076
CMW 14025 N. ribis S. cordatum
Kwambonambi, S. Africa D. Pavlic DQ316080
CMW 13992
c N. ribis S. cordatum
Sodwana bay, S. Africa D. Pavlic CMW 9081
ICMP 8003 Neofusicoccum parvum Populus nigra
New Zealand G.J. Samuels AY236943
CMW 9078 ICMP 7925 N. parvum Actinidia deliciosa
New Zealand S.R. Pennycook AY236940
CMW 994 ATCC 58189 N. parvum Malus sylvestris
New Zealand G.J. Samuels AF243395
CMW 9071 N. parvum Ribes
sp. Australia M.J. Wingfield AY236938 CMW 10122 N. parvum Eucalyptus grandis
Mpumalanga, S. Africa H. Smith AF283681
CMW 14030 c N. parvum S. cordatum
Kwambonambi, S. Africa D. Pavlic DQ316077
CMW 14029
CBS 118832 N. parvum S. cordatum
Kwambonambi, S. Africa D. Pavlic DQ316078
CMW 14097 c N. parvum S. cordatum
St. John’s Port, S. Africa D. Pavlic CMW 7801
BRIP 23396 Neofusicoccum mangiferae Mangifera indica
Australia G.I. Johnson AY615187
CMW 7024 BRIP 24101 N. mangiferae M. indica
Australia G.I. Johnson AY615185
CMW 13998 CBS 118821 N. mangiferae S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316081
CMW 14005 N. mangiferae S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316082
CMW 14102 c N. mangiferae S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316083
CMW 14034 c N. mangiferae S. cordatum Kwambonambi, S. Africa D. Pavlic CMW 9072
Neofusicoccum australe Acacia sp. Melbourne, Australia J. Roux & D. Guest AY339260
CMW 6837 N. australe Acacia sp. Batemans Bay, Australia M.J. Wingfield AY339262
CMW 1110 N. australe Widdringtonia nodiflora Cape province, S. Africa W.J. Swart AY615166
CMW 1112 N. australe W. nodiflora Cape province, S. Africa W.J. Swart AY615167
CMW 3386 N. australe Wollemia nobilis Queensland, Australia M. Ivory AY615165
CMW 14074 N. australe S. cordatum East London, S. Africa D. Pavlic DQ316089
CMW 13986 CBS 118839 N. australe S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316085
CMW 13987 c N. australe S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316086
CMW 14013 c N. australe S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316087
CMW 9076 ICMP 7818 Neofusicoccum luteum Malus domestica New Zealand S.R. Pennycook AY236946
CMW 992 KJ 93·52
N. luteum Actinidia deliciosa New Zealand G.J. Samuels AF027745
CMW 10309 CAP 002
N. luteum Vitis vinifera Portugal
A.J.L. Phillips AY339258
CMW 14071 c CBS 118842 N. luteum S. cordatum East London, S. Africa D. Pavlic DQ316088
CMW 14073 c N. luteum S. cordatum East London, S. Africa D. Pavlic DQ316090
CMW 10125 Neofusicoccum eucalyptorum E. grandis Mpumalanga, S. Africa H. Smith AF283686
CMW 11705 N. eucalyptorum E. nitens South Africa B. Slippers AY339248
Plant Pathology (2007)
56 , 624
–636 Botryosphaeriaceae on Myrtaceae in South Africa 627
PP A_1608 CMW 9075
ICMP 8019 Botryosphaeria dothidea P. nigra New Zealand G.J. Samuels AY236950
CMW 8000 B. dothidea Prunus sp. Crocifisso, Switzerland B. Slippers AY236949
CMW 14009 c CBS 118831 B. dothidea S. cordatum Sodwana Bay, S. Africa D. Pavlic DQ316084
CMW 10130 Lasiodiplodia theobromae Vitex donniana Uganda
J. Roux AY236951
CMW 9074 L. theobromae Pinus sp. Mexico
T. Burgess AY236952
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