Papers by Draginja Pavlic
Abstract: Botryosphaeria spp. are common and widely distributed pathogens on many economically im... more Abstract: Botryosphaeria spp. are common and widely distributed pathogens on many economically important crops, includ-ing forest tree species. These fungi cause a wide variety of symptoms on trees of all ages, but are mostly associated with canker and die-back of branches and main stems. As disease agents, Botryosphaeria spp. are often encountered in their anamorph state, namely species of Fusicoccum, Diplodia or Lasiodiplodia. During a recent survey of botryosphaeriaceous fungi from native Syzygium cordatum in South Africa, an unfamiliar Lasiodiplodia sp. was isolated. The aim of this study was to compare this apparently undescribed species with other species of Botryosphaeria using morphological characteristics and DNA sequence data of the rDNA internal transcribed spacers, ITS1 and ITS2. Based on sequence data, the isolates from S. cordatum were more closely related to B. rhodina (anamorph Lasiodiplodia theobromae) than to other Botryosphaeria spp., but also phylogenetically dis...
Fungal Ecology, 2015
Plants and animals adapted to colonize disturbed sites might also be better invaders, but this ph... more Plants and animals adapted to colonize disturbed sites might also be better invaders, but this phenomenon has not been widely considered in fungi. We investigated genetic diversity and structure amongst isolates of Neofusicoccum parvum, N. cordaticola, N. kwam-bonambiense and N. umdonicola that coexist sympatrically on a native tree, Syzygium cor-datum, across its distribution in South Africa. Species composition varied among stands, with dominance of N. parvum in disturbed stands, and absence in undisturbed stands, where the other species dominated. N. parvum populations from trees planted in urban environments were more genetically diverse than populations from human disturbed stands of S. cordatum. Bayesian analysis clustered N. parvum isolates in three sub-populations, suggesting three sources of origin. These results support the hypothesis that as a generalist N. parvum will dominate human disturbed sites and trees in urban areas, indicating strong potential for invasion, and its spreading from non-native hosts to native S. cordatum, rather than vice versa.
Southern Forests: a Journal of Forest Science, 2009
The fungal family Botryosphaeriaceae includes thousands of described species from around the worl... more The fungal family Botryosphaeriaceae includes thousands of described species from around the world that occur on various, primarily woody hosts (von Arx 1987, Index Fungorum Partnership 2004, Crous et al. 2006). Many species of the Botryosphaeriaceae are known as pathogens, most commonly causing die-back and canker diseases on twigs, branches and trunks of trees, and more rarely diseases such as seed-capsule abortion, witchesbroom, leaf diseases, seedling diseases and root cankers (Sinclair and Lyon 2005, Slippers and Wingfield 2007). Species of Botryosphaeriaceae are, however, treated as opportunistic pathogens, because the diseases they cause are almost always associated with stress or wounding to their host plants. Despite their pathogenic abilities, Botryosphaeriaceae are also well known as endophytes of above-ground parts of woody plants, apparently existing for long periods of time in the absence of symptoms (Slippers and Wingfield 2007). Eucalyptus species, both in their native and introduced ranges, are known to be commonly infected by various species of the Botryosphaeriaceae (Smith et al. 1994, Slippers et al. 2004a, Burgess et al. 2005, Mohali et al. 2007, and others cited in the remainder of this paper). While these fungi are often not as aggressive as some primary pathogens, the die-back and canker diseases caused by Botryosphaeriaceae on Eucalyptus are amongst the most The Botryosphaeriaceae cause endophytic infections of leaves and bark of various trees, including Eucalyptus, and they apparently persist in this state for extended periods of time. Under conditions of stress, these fungi cause many different disease symptoms on Eucalyptus, of which stem and branch cankers and die-back are the most prominent. Given their cryptic, endophytic nature, the Botryosphaeriaceae are easily overlooked when moving seeds and plants around the world. It is, therefore, not surprising to see a growing number of examples of introductions of Botryosphaeriaceae into new environments. In the past, three species were commonly reported from Eucalyptus, namely Botryosphaeria dothidea, Neofusicoccum ribis (reported as B. ribis) and Lasiodiplodia theobromae. It is now known that B. dothidea and N. ribis are generally rare on Eucalyptus, and that Aplosporella yalgorensis, B.
Plant Pathology, 2011
The Botryosphaeriaceae is a species-rich family that includes pathogens of a wide variety of tree... more The Botryosphaeriaceae is a species-rich family that includes pathogens of a wide variety of trees, including Eucalyptus species. Symptoms typical of infection by the Botryosphaeriaceae have recently been observed in Eucalyptus plantations in South China. The aim of this study was to identify the Botryosphaeriaceae associated with these symptoms. Isolates were collected from branch cankers and senescent twigs of different Eucalyptus spp. All isolates resembling Botryosphaeriaceae were separated into groups based on conidial morphology. Initial identifications were made using PCR-RFLP fingerprinting, by digesting the ITS region of the rDNA operon with the restriction enzymes CfoI and KspI. Furthermore, to distinguish isolates in the Neofusicoccum parvum/N. ribis complex, a locus (BotF15) previously shown to define these species, was amplified and restricted with CfoI. Selected isolates were then identified using comparisons of DNA sequence data for the ITS rDNA and translation elongation factor 1-alpha (TEF-1α) gene regions. Based on anamorph morphology and DNA sequence comparisons, five species were identified: Lasiodiplodia pseudotheobromae, L. theobromae, Neofusicoccum parvum, N. ribis sensu lato and one undescribed taxon, for which the name Fusicoccum fabicercianum sp. nov. is provided. Isolates of all species gave rise to lesions on the stems of an E. grandis clone in a glasshouse inoculation trial and on the stems of five Eucalyptus genotypes inoculated in the field, where L. pseudotheobromae and L. theobromae were most pathogenic. The five Eucalyptus genotypes differed in their susceptibility to the Botryosphaeriaceae species suggesting that breeding and selection offers opportunity for disease avoidance in the future.
Plant Pathology, 2007
Eight species of the Botryosphaeriaceae (canker and dieback pathogens) were identified on native ... more 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, were more pathogenic on the 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
Mycologia, 2008
In this study seven new species of the Botryosphaeriaceae are described from baobab (Adansonia gi... more In this study seven new species of the Botryosphaeriaceae are described from baobab (Adansonia gibbosa) and surrounding endemic tree species growing in the Kimberley region of northwestern Australia. Members of the Botryosphaeriaceae were predominantly endophytes isolated from apparently healthy sapwood and bark of endemic trees; others were isolated from dying branches.
Molecular Phylogenetics and Evolution, 2009
Neofusicoccum parvum and N. ribis (Botryosphaeriaceae, Ascomycetes) are closely related, plant pa... more Neofusicoccum parvum and N. ribis (Botryosphaeriaceae, Ascomycetes) are closely related, plant pathogenic fungi with a worldwide distribution on a wide range of woody hosts. Species boundaries in the N. parvum/N. ribis complex have eluded definition, despite the application of various tools for characterisation. In this study, we test the hypothesis that only one species exists amongst isolates from the N.parvum/N. ribis complex, identified from Syzygium cordatum trees across their native distribution in South Africa. Genealogical concordance phylogenetic species recognition (GCPSR) was applied based on concordance of genealogies obtained from DNA sequence data for five nuclear loci. These data showed that the single species hypothesis must be rejected. Rather, all analyses support the existence of three previously unrecognised, cryptic species within the N. parvum/N. ribis complex from S. cordatum, in addition to N. parvum and N. ribis. The three lineages reflecting these cryptic taxa are sympatric across their geographical range, indicating barriers to gene flow other than geographic isolation. Phenotypic characters failed to detect all the species uncovered by the GCPSR. Sequence data of the Internal Transcribed Spacer (ITS) of the ribosomal DNA locus, which is thought to be useful for barcoding in fungi, did not distinguish all the species with confidence. RNA polymerase II subunit (RPB2) was the most informative to distinguish all the species a posteriori to the application of GCPSR. The results reflect the critical importance of using multiple gene genealogies and adequate sampling to identify cryptic species and to characterise the true diversity within the Botryosphaeriaceae.
European Journal of Forest Research, 2010
Unusual and extensive dieback of European hop hornbeam (Ostrya carpinifolia) has been observed in... more Unusual and extensive dieback of European hop hornbeam (Ostrya carpinifolia) has been observed in western Slovenia and northern Italy in recent years, when extreme drought and higher temperatures were recorded. A preliminary study identified Botryosphaeria dothidea as a potential causative agent of the dieback. Further characterization of intra-and interspecies diversity of Botryosphaeriaceae collected from O. carpinifolia and other tree species in the affected area was achieved based on anamorph morphology, sequence data from the ITS rDNA and EF1-α, PCR-RFLP analysis and AFLP profiles. The majority of the isolates analyzed were identified as B. dothidea, and in vitro pathogenicity tests reconfirmed the fungus to be an important cause of the disease. Insight into the B. dothidea population, diversity based on AFLP markers indicates that the dieback observed in O. carpinifolia is probably associated with a heterogenous population of B. dothidea, which emerged from a latent state in response to changed climate conditions. Isolates with Dothiorella-like conidia were also identified during the survey, but these were collected more rarely and appear to represent undescribed species. Isolates from Dothiorella genus expressed low pathogenicity in pathogenicity tests and proved no impact on the pathogenic ability of B. dothidea.
Botryosphaeria spp. are common and widely distributed pathogens on many economically important cr... more Botryosphaeria spp. are common and widely distributed pathogens on many economically important crops, including forest tree species. These fungi cause a wide variety of symptoms on trees of all ages, but are mostly associated with canker and die-back of branches and main stems. As disease agents, Botryosphaeria spp. are often encountered in their anamorph state, namely species of Fusicoccum, Diplodia or Lasiodiplodia. During a recent survey of botryosphaeriaceous fungi from native Syzygium cordatum in South Africa, an unfamiliar Lasiodiplodia sp. was isolated. The aim of this study was to compare this apparently undescribed species with other species of Botryosphaeria using morphological characteristics and DNA sequence data of the rDNA internal transcribed spacers, ITS1 and ITS2. Based on sequence data, the isolates from S. cordatum were more closely related to B. rhodina (anamorph Lasiodiplodia theobromae) than to other Botryosphaeria spp., but also phylogenetically distinct from this species. Conidia of the species from S. cordatum were also different to those of L. theobromae. We conclude that the isolates from S. cordatum represent an undescribed Lasiodiplodia sp. and provide the name Lasiodiplodia gonubiensis for it.
New species of the Botryosphaeriaceae were identified and described in this study. Isolates were ... more New species of the Botryosphaeriaceae were identified and described in this study. Isolates were collected from baobab (Adansonia gibbosa) and surrounding endemic tree species growing in north-western Australia. Cultures resembling those of the Botryosphaeriaceae were predominantly endophytes isolated from apparently healthy wood and bark, but some also came from dying branches. Based on phylogenetic analyses of ITS and EF1-a sequence data, isolates were placed in clades representing the genera Pseudofusicoccum, Botryosphaeria, Lasiodiplodia, Dothiorella and Neoscytalidium. Sequence comparison with known species of the Botryosphaeriaceae revealed that several isolates obtained in this study represent undescribed species. The new taxa were characterised based on ITS and EF1-a sequence data combined with anamorph morphology. Six new species are recognised including three Pseudofusicoccum spp., a Botryosphaeria sp., a Lasiodiplodia sp. and a Dothiorella sp. Neoscytalidium isolates from this study formed a separate sub-clade in this genus, but a lack of sequences for previously described Neoscytalidium spp. Precludes their identification at this stage. Very few studies have been conducted to identify Botryosphaeriaceae on trees in natural ecosystems, and almost nothing is known regarding the fungi on baobabs. Thus, the relatively large number of new species emerging from this study is not surprising. The role of these fungi in the ecology of the trees from which they were collected will be considered in future studies.
South African Journal of Botany, 2010
(neem), Lavandula angustifolia (English lavender), Cucumis metuliferus (wild cucumber), Lippia ja... more (neem), Lavandula angustifolia (English lavender), Cucumis metuliferus (wild cucumber), Lippia javanica (fever tree) and Capsicum frutescens (red chili) were evaluated against three common onion pathogens namely Rhizoctonia solani, Colletotrichum gloeosporioides and Fusarium oxysporum in vitro. Acetone leaf extracts of L. javanica, L. angustifolia and A. indica showed significant antifungal activity at 2.5 and 5.0 mg/ml against all three fungi. All the extracts of C. frutescens showed antifungal activity against C. gloeosporioides. Extracts of C. metuliferus had some activity against the C. gloeosporioides and F. oxysporum but not comparable to the activity of the other extracts. Antifungal activity of L. javanica and L. angustifolia correlates well with the activity shown in the direct bioassay on TLC plates. There were three compounds (medium polarity) within the L. angustifolia extract and two compounds (polar) within the L. javanica extract which inhibited the growth of all the fungi. Seed treatment tests, in R. solani inoculated soil, indicated higher seedling survival rate and average seedling mass when the seeds were treated with A. indica extract. The implementation of the selected plant extracts as a bio-control agent will reduce production costs.
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Papers by Draginja Pavlic