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1.
A dramatic decline averaging 43% over a 4‐year period has occurred in tree Euphorbia (Euphorbia tetragona and Euphorbia triangularis) populations on the Great Fish River Reserve, South Africa. These changes are evident from data gathered by general vegetation monitoring methods as well as from a focused study of four tree Euphorbia populations. The decline from 2003 to 2007 was more marked for E. triangularis than for E. tetragona and was accompanied by a general absence of seedlings and a reduced presence of younger age classes of both species, decreasing the proportion of younger trees in the populations. The role of megaherbivores, specifically the black rhinoceros, in these changes is well established. However, the impact of baboon activity, leading to damage to tree crowns and upper branches, is also substantial, especially on E. triangularis populations. Damaged crowns were recorded significantly more often for E. triangularis than for E. tetragona, and the damage frequency increased with decreasing tree height. Thus, our work provides the first evidence that these two closely related Euphorbia species may be affected differently by herbivory.  相似文献   

2.
Entomochoric spore dispersal is well-documented for most ophiostomatoid fungal genera, most of which are associated with bark or ambrosia beetles. Gondwanamyces spp. are unusual members of this group that were first discovered in the flower heads of the primitive angiosperm genus Protea, that is mostly restricted to the Cape Floristic region of Africa. In this study, we present the discovery of the vectors of Gondwanamyces proteae in Protea repens infructescences, which were identified using PCR, direct isolation, and light microscopy. Gondwanamyces proteae DNA and ascospores were identified on diverse lineages of arthropods including beetles (Euderes lineicolis and Genuchus hottentottus), bugs (Oxycarenus maculates), a psocopteran species and five mite (Acari) species. Based on isolation frequency, however, a mite species in the genus Trichouropoda appears to be the most common vector of G. proteae. Gondwanamyces spores were frequently observed within pit mycangia at the base of the legs of these mites. Manipulative experiments demonstrated the ability of mites to carry viable G. proteae spores whilst in transit on the beetle G. hottentottus and that these mites are able to transfer G. proteae spores to uncolonised substrates in vitro. Interestingly, this same mite species has also been implicated as vector of Ophiostoma spores on P. repens and belongs to the same genus of mites that vector Ophiostoma spp. associated with pine-infesting bark beetles in the Northern Hemisphere.  相似文献   

3.
Mehl JW  Slippers B  Roux J  Wingfield MJ 《Mycologia》2011,103(3):534-553
There have been several recent reports of Pterocarpus angolensis (kiaat) trees dying in South Africa, Zambia and Zimbabwe, where this tree is used in traditional medicine and is a valuable source of timber for woodcarving and furniture. A survey of material from diseased P. angolensis trees in South Africa yielded isolates of the Botryosphaeriaceae, an important fungal family known to cause a number of tree diseases. The aim of this study was to identify these Botryosphaeriaceae and to determine their pathogenicity to P. angolensis with branch inoculations. Seven species of the Botryosphaeriaceae were identified based on a combination of morphological characteristics and sequences from the ITS and EF-1α gene regions. Four of these represent undescribed taxa for which the names Pseudofusicoccum violaceum, P. olivaceum, Diplodia alatafructa and Fusicoccum atrovirens are provided. The remaining three species collected include Lasiodiplodia theobromae, L. pseudotheobromae and L. crassispora. Inoculation trials on tree branches showed that L. pseudotheobromae and one isolate of D. alatafructa differed significantly from control inoculations. The high levels of virulence and common occurrence of L. pseudotheobromae suggest that this species could play a role in tree dieback and death.  相似文献   

4.
Estimations of global fungal diversity are hampered by a limited understanding of the forces that dictate host exclusivity in saprobic microfungi. To consider this problem for Gondwanamyces and Ophiostoma found in the flower heads of Protea in South Africa, we determined the role of various factors thought to influence their host exclusivity. Results showed that various biotic and abiotic factors influence the growth and survival of these fungi in vitro. Monitoring temperature and relative humidity (RH) fluctuations within infructescences in vivo revealed considerable microclimatic differences between different Protea spp. Fungal growth and survival at different RH levels experienced in the field suggested that this factor does not play a major role in host exclusivity of these fungi. Maximum temperatures within infructescences and host preferences of the vectors of Gondwanamyces and Ophiostoma appear to play a substantial part in determining colonisation of Protea in general. However, these factors did not explain host exclusivity of specific fungal species towards particular Protea hosts. In contrast, differential growth of fungal species on media containing macerated tissue of Protea showed that Gondwanamyces and Ophiostoma grow best on tissue from their natural hosts. Thus, host chemistry plays a role in host exclusivity of these fungi, although some species grew vigorously on tissue of Protea spp. with which they are not naturally associated. A combination of host chemistry and temperature partially explains host exclusivity, but the relationship for these factors on the tested saprobic microfungi and their hosts is clearly complex and most likely includes combinations of various biotic and abiotic factors including those emerging from this study.  相似文献   

5.
Chen S  Gryzenhout M  Roux J  Xie Y  Wingfield MJ  Zhou X 《Mycologia》2011,103(6):1384-1410
Many species in the Cryphonectriaceae cause diseases of trees, including those in the genera Eucalyptus and Syzygium. During disease surveys on these trees in southern China, fruiting structures typical of fungi in the Cryphonectriaceae and associated with dying branches and stems were observed. Morphological comparisons suggested that these fungi were distinct from the well known Chrysoporthe deuterocubensis, also found on these trees in China. The aim of this study was to identify these fungi and evaluate their pathogenicity to Eucalyptus clones/species as well as Syzygium cumini. Three morphologically similar fungal isolates collected previously from Indonesia also were included in the study. Isolates were characterized based on comparisons of morphology and DNA sequence data for the partial LSU and ITS nuclear ribosomal DNA, β-tubulin and TEF-1α gene regions. After glasshouse trials to select virulent isolates field inoculations were undertaken to screen different commercial Eucalyptus clones/species and S. cumini trees for susceptibility to infection. Phylogenetic analyses showed that the Chinese isolates and those from Indonesia reside in a clade close to previously identified South African Celoporthe isolates. Based on morphology and DNA sequence comparisons, four new Celoporthe spp. were identified and they are described as C. syzygii, C. eucalypti, C. guangdongensis and C. indonesiensis. Field inoculations indicated that the three Chinese Celoporthe spp., C. syzygii, C. eucalypti and C. guangdongensis, are pathogenic to all tested Eucalyptus and S. cumini trees. Significant differences in the susceptibility of the inoculated Eucalyptus clones/species suggest that it will be possible to select disease-tolerant planting stock for forestry operations in the future.  相似文献   

6.
The impact of black rhinoceros (Bicornis diceros minor) on the tree euphorbias Euphorbia tetragona and Euphorbia triangularis was studied in the Great Fish River Reserve, South Africa. Black rhinoceros pushed over about 5–7% of the trees in a 2‐month period. There was a preference of rhinos for smaller trees, however this preference did not guarantee euphorbia survival in the larger size classes. This means that tree euphorbias could very well disappear from all areas accessible to rhinos. Rhino feeding choices were correlated with higher plant moisture content, higher nitrogen content, and a higher digestibility.  相似文献   

7.
Damm U  Crous PW  Fourie PH 《Mycologia》2007,99(5):664-680
Botryosphaeriaceae are common dieback and canker pathogens of woody host plants, including stone fruit trees. In the present study the diversity of members of the Botryosphaeriaceae isolated from symptomatic wood of Prunus species (plum, peach, nectarine and apricot) was determined in stone fruit-growing areas in South Africa. Morphological and cultural characteristics as well as DNA sequence data (5.8S rDNA, ITS-1, ITS-2 and EF-1a) were used to identify known members and describe novel members of Botryosphaeriaceae. From the total number of wood samples collected (258) 67 isolates of Botryosphaeriaceae were obtained, from which eight species were identified. All species were associated with wood necrosis. Diplodia seriata (= "Botryosphaeria" obtusa) was dominant, and present on all four Prunus species sampled, followed by Neofusicoccum vitifusiforme and N. australe. First reports from Prunus spp. include N. vitifusiforme, Dothiorella viticola and Diplodia pinea. This is also the first report of D. mutila from South Africa. Two species are newly described, namely Lasiodiplodia plurivora sp. nov. from P. salicina and Diplodia africana sp. nov. from P. persica. All species, except Dothiorella viticola, caused lesions on green nectarine and/or plum shoots in a detached shoot pathogenicity assay.  相似文献   

8.
Several species of Botr yosphaeria are known to occur on grapevines, causing a wide range of disorders including bud mortality, dieback, brown wood streaking and bunch rot. In this study the 11 Botryosphaeria spp. associated with grapevines growing in various parts of the world, but primarily in South Africa, are distinguished based on morphology, DNA sequences (ITS-1, 5.8S, ITS-2 and EF1-α) and pathological data. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina and a Diplodia sp. are confirmed from grapevines in South Africa, while Diplodia porosum, Fusicoccum viticlavatum and F. vitifusiforme are described as new. Although isolates of B. dothidea and B. stevensii are confirmed from grapevines in Portugal, neither of these species occurred in South Africa, nor were any isolates of B. ribis confirmed from grapevines. All grapevine isolates from Portugal, formerly presumed to be B. ribis, are identified as B. parva based on their EF1-α equence data. From artificial inoculations on grapevine shoots, we conclude that B. australis, B. parva, B. ribis and B. stevensii are more virulent than the other species studied. The Diplodia sp. collected from grapevine canes is morphologically similar but phylogenetically distinct from D. sarmentorum. Diplodia sarmentorum is confirmed as anamorph of Otthia spiraeae, the type species of the genus Otthia (Botryosphaeriaceae). A culture identified as O. spiraeae clustered within Botryosphaeria and thus is regarded as probable synonym. These findings confirm earlier suggestions that the generic concept of Botryosphaeria should be expanded to include genera with septate ascospores and Diplodia anamorphs.  相似文献   

9.
Genetic diversity of 50 isolates of Neofusicoccum parvum, the predominant species of the Botryosphaeriaceae recovered from grapevines displaying symptoms of dieback and decline in New Zealand, was compared to that of isolates from Australia, South Africa, and California. The eight universally primed polymerase chain reaction (UP-PCR) primers distinguished 56 genotypes, with only four clonal pairs found. Seven main groups were identified in a neighbour-joining (NJ) tree with isolates from different regions and vineyards of New Zealand, Australia, and California distributed in different groups, indicating a high level of intra and intervineyard genetic variation. All of the South African isolates were positioned in a separate UP-PCR group, indicating that these isolates were less related to the other N. parvum isolates. When compared to fungi that reproduce sexually the genetic diversity and Shannon diversity indices were low (0.076-0.249; 0.109-0.367, respectively), genetic identity levels were high (0.76-0.95), and genetic distance levels were low (0.04-0.27). The large number of genotypes and the low number of clones in the New Zealand N. parvum populations may be explained by parasexual recombination as anastomosis was observed between nonself pairings. Pathogenicity tests using isolates from different UP-PCR groups inoculated onto either green shoots or 1-y-old grapevines detected virulence diversity, indicating intra and intervineyard variation between isolates, however, no correlation was detected between UP-PCR group and virulence.  相似文献   

10.
Pineapple (Ananas comosus) is native to South America and widely planted as a fruit crop in the tropics and sub-tropics. This plant is susceptible to a number of fungal diseases of which the most severe is fusariosis. The disease is caused by Fusarium guttiforme and occurs only in South and Central America. The occurrence of a similar disease on pineapples in South Africa has prompted a re-evaluation of the Fusarium sp. associated with pineapple fruit rot. Phylogenetic relationships of isolates from pineapples collected in Brazil and South Africa were assessed based on sequence data for the translation elongation factor-1-α, histone H3 and β-tubulin gene regions. Analyses showed that the South African isolates represent a species distinct from Brazilian isolates. The South African isolates are characterised by a concentration of aerial mycelium at the centres of the colonies, different to the Brazilian isolates that have an even distribution of aerial mycelium. Both phylogenetic and morphological data show that the disease on pineapple in South Africa is caused by a new Fusarium species described here as F. ananatum sp. nov.  相似文献   

11.
The genus Pythium is important in agriculture, since it contains many plant pathogenic species, as well as species that can promote plant growth and some that have biocontrol potential. In South Africa, very little is known about the diversity of Pythium species within agricultural soil, irrigation and hydroponic systems. Therefore, the aim of the study was to characterise a selection of 85 Pythium isolates collected in South Africa from 1991 through to 2007. The isolates were characterised morphologically as well as through sequence and phylogenetic analyses of the internal transcribed spacer regions (ITS) and the 5.8S gene of the nuclear ribosomal DNA. Phylogenetic analyses showed that the isolates represented ten of the 11 published Pythium clades [Lévesque & De Cock, 2004. Molecular phylogeny and taxonomy of the genus Pythium. Mycological Research 108: 1363–1383]. Characterisation of isolates in clade D and J suggested that the phylogenetic concept of Pythium acanthicum and Pythium perplexum respectively, needs further investigation in order to enable reliable species identification within these clades. Our phylogenetic analyses of Pythium species in clade B also showed that species with globose sporangia group basal within this clade, and are not dispersed within the clade as previously reported. The 85 South African isolates represented 34 known species, of which 20 species have not been reported previously in South Africa. Additionally, three isolates (PPRI 8428, 8300 and 8418) were identified that may each represent putative new species, Pythium sp. WJB-1 to WJB-3.  相似文献   

12.
Causative fungi of net-type and spot-type lesions on barley were isolated and identified as anamorphs of Pyrenophora teres and Pyrenophora japonica respectively. Comparison of morphological characteristics showed that isolates of the two species are separable on the basis of differences in colony texture, conidiophore shape, conidial arrangement and conidial dimensions. The two species could also be distinguished from each other on account of adult-plant reactions exhibited by Dampier barley after inoculation by various isolates from South Africa, one isolate from Germany and one isolate from Washington State in North America.  相似文献   

13.
Species in the fungal family Botryosphaeriaceae are latent pathogens on woody trees. These fungi often have a wide host range, which can include native and introduced hosts in an area. Multi-locus DNA sequence identification on a recent collection of Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum trees in South Africa revealed cross-infectivity of several species, novel host associations and new country reports. Neofusicoccum eucalyptorum, Neofusicoccum kwambonambiense, Neofusicoccum parvum, Neofusicoccum australe and Lasiodiplodia pseudotheobromae were identified from both tree species, with L. pseudotheobromae and N. eucalyptorum isolated for the first time from S. cordatum, similar to N. kwambonambiense from Eucalyptus. This also represents the first report of L. pseudotheobromae from South Africa. Botryosphaeriaceae species on Eucalyptus species and S. cordatum are fairly well known from South Africa. However, this study revealed new associations, indicating that conclusions should not be generalized and that more intensive sampling from different areas and over time is likely to reveal distinct species and host association patterns.  相似文献   

14.
The emergence of wattle wilt disease on non-native Acacia mearnsii trees in Africa, caused by the indigenous fungus Ceratocystis albifundus, has highlighted a need to better understand the diversity, ecology and distribution of Ceratocystis species in natural African environments. In this study we applied phylogenetic inference to identify and characterize isolates of Ceratocystis collected in a natural savanna ecosystem in South Africa. Three new species were recognized and are described as C. cryptoformis sp. nov. in the C. moniliformis complex, as well as C. thulamelensis sp. nov. and C. zambeziensis sp. nov., both residing in the C. fimbriata complex. Incorporating the new species into global phylogenies of Ceratocystis provided insights into the patterns of evolution and biogeography of this group of fungi. Notably, the African continent was identified as an important centre of diversification of Ceratocystis spp., from which several lineages of these fungi were shown to have radiated.  相似文献   

15.
Elephant and fire are considered to be among the most important agents that can modify the African savanna ecosystem. Although the synergistic relationship between these two key ecological drivers is well documented, it has proved much more difficult to establish the relative effects they have on savanna vegetation structure at a fine-scale over time. In this study, we explore the comparative impacts of fire and elephant on 2,522 individually identified large trees (≥5 m in height) in the Kruger National Park, South Africa. Data were collected from 21 transects first surveyed in April 2006 and resurveyed in November 2008, to determine the relative importance of past damage by these agents on subsequent impacts and mortality. The occurrence of fire or elephant damage in 2006 affected the amount of tree volume subsequently removed by both these agents; elephant removed more tree volume from previously burned trees and the impact of subsequent fire was higher on previously burned or elephant-utilized trees than on undamaged trees. Mortality was also affected by an interaction between previous and recent damage, as the probability of mortality was highest for trees that suffered from fire or elephant utilization after being pushed over. Subsequent fire damage, but not elephant utilization, on debarked trees also increased the probability of mortality. Mortality was twice (4.6% per annum) that of trees progressing into the ≥5 m height class, suggesting an overall decline in large tree density during the 30-month study period. The responses of large trees were species and landscape-specific in terms of sensitivity to elephant and fire impacts, as well as for levels of mortality and progression into the ≥5 m height class. These results emphasize the need for fine-scale site-specific knowledge for effective landscape level understanding of savanna dynamics.  相似文献   

16.
Blignaut E 《Mycopathologia》2007,163(2):67-73
South Africa currently has an estimated 500,000 AIDS orphans, many of whom are HIV-positive. Oral candidiasis commonly occurs in both adult and paediatric HIV/AIDS patients. Published information on HIV-positive children in Africa mainly concerns hospitalised patients. The objective of this study was to determine the prevalence of oral candidiasis and oral yeast carriage among paediatric HIV/AIDS patients residing in orphanages in Gauteng, South Africa, and to compare the prevalence of isolated yeast species with species obtained from adult HIV/AIDS patients. Eighty-seven paediatric HIV/AIDS patients residing in five homes were examined and a swab taken from the dorsal surface of the tongue, cultured on CHROMagar and yeast isolates identified with the ATB 32C commercial system. The species prevalence of 57 identified isolates was compared with that of 330 isolates from adult HIV/AIDS patients. Twelve (13.8%) children presented with clinically detectable candidiasis. Yeasts were isolated from 0% to 53% of children in the individual homes, with Candida albicans (40.4%) and C. dubliniensis (26.3%) constituting the most frequently isolated species. Gentian violet prophylaxis was administered in one particular home and a higher carriage rate (66.6%) of non-C. albicans and non-C. dubliniensis was observed among these children. The prevalence of C. albicans was lower while the prevalence of C. dubliniensis, C. glabrata and C. tropicalis was significantly higher (p ≤ 0.001) among the children than among adult HIV/AIDS patients. These findings indicate a role for yeast culture and species determination in cases with candidiasis in institutionalized paediatric HIV/AIDS patients.  相似文献   

17.
In West Africa, Trichinella infection was documented in humans and animals from Senegal in the 1960s, and the biological characters of one isolate showed a lower infectivity to domestic pigs and rodents when compared with that of a Trichinella spiralis pig isolate from Europe. To identify the Trichinella species present in West Africa, a survey was conducted in a total of 160 wild animals in the Republic of Guinea. Three Viverridae, one true civet (Viverra civetta) and two African palm civets (Nandinia binotata) from the Fouta Djallon Massif, Pilimini Subprefecture, were found positive by artificial digestion of muscle samples. Trichinella larvae from these three viverrids were identified as Trichinella britovi and no difference was detected in three examined sequences from these African isolates and the reference strain of T. britovi from Europe, indicating common ancestry, an historically continuous geographic distribution, and recent isolation for African and European populations. The detection of T. britovi in West Africa modifies our knowledge about the distribution of encapsulated species of Trichinella in Africa. Thus, Trichinella nelsoni is now considered to have a distribution limited to the Eastern part of the Afrotropical region from Kenya to South Africa. This provides a plausible explanation for the presence of Trichinella T8 in Namibia and South Africa, and further suggests that T. britovi could be the Trichinella species circulating among wild animals of Northern Africa.  相似文献   

18.
Species in the Botryosphaeriaceae represent some of the most important fungal pathogens of woody plants. Although these fungi have been relatively well studied on economically important crops, hardly anything is known regarding their taxonomy or ecology on native or non-commercial tree species. The aim of this study was to compare the diversity and distribution of the Botryosphaeriaceae on Terminalia catappa, a tropical tree of Asian origin planted as an ornamental in Cameroon, Madagascar and South Africa. A total of 83 trees were sampled, yielding 79 Botryosphaeriaceae isolates. Isolates were initially grouped based on morphology of cultures and conidia. Representatives of the different morphological groups were then further characterised using sequence data for the ITS, tef 1-alpha, rpb2, BOTF15 and beta-tub gene regions. Five species of the Botryosphaeriaceae were identified, including Neofusicoccum parvum, N. batangarum sp. nov., Lasiodiplodia pseudotheobromae, L. theobromae and L. mahajangana sp. nov. Lasiodiplodia pseudotheobromae and L. theobromae, were the most commonly isolated species (62%), and were found at all the sites. Neofusicoccum parvum and N. batangarum were found in South Africa and Cameroon, respectively, whereas L. mahajangana was found only in Madagascar. Greenhouse inoculation trials performed on young T. catappa trees showed variation among isolates tested, with L. pseudotheobromae being the most pathogenic. The Botryosphaeriaceae infecting T. catappa appear to be dominated by generalist species that also occur on various other hosts in tropical and sub-tropical climates.  相似文献   

19.
Coniothyrium canker caused by Coniothyrium zuluense, is a serious stem canker disease of Eucalyptus species in sub-tropical regions of South Africa. This disease is typified by necrotic bark lesions that coalesce to form large kino-impregnated cankers along the stems of trees. The strategy currently used to manage Coniothyrium canker in plantations is to deploy Eucalyptus species or clones that are resistant to the disease. Considerable success has already been achieved in this regard, but the long-term durability of resistance is of concern. Thus, forest managers are interested in the genetic diversity of the pathogen and its potential to overcome disease resistance in planting stock. In this study, 344 isolates of C. zuluense from different plantation regions in South Africa were compared on the basis of colony colour, conidial morphology, growth characteristics on agar and pathogenicity to a susceptible E. grandis clone. Conidia of all C. zuluense isolates measured were similar in size and shape. The fungus is slow growing in culture, which is indicative of its apparent biotrophic habit, with optimum growth observed at 30 °C. Isolates of C. zuluense displayed considerable variation in colony colour and pathogenicity in inoculation trials. Variation in morphology and pathogenicity amongst isolates suggests that C. zuluense has been present in South Africa for an extended period of time, or that it is changing rapidly due to strong directional selection pressures. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

20.
Botryosphaeria lutea (anamorph Fusicoccum luteum) most easily is distinguished from other Botryosphaeria spp. by a yellow pigment that is formed in young cultures. This fungus has been reported from a number of cultivated hosts in New Zealand and Portugal. During a survey of Botryosphaeria fungi that occur on native Acacia species in Australia, a yellow pigment was observed in some cultures. These isolates were morphologically similar to B. lutea, but the pigment differed slightly from the one formed by authentic B. lutea isolates. Preliminary data also revealed small differences in ITS rDNA sequence data. The aim of this study was to determine whether these small differences were indicative of separate species or merely variations within B. lutea. Anamorph, teleomorph and culture morphology were compared between B. lutea and Acacia isolates from Australia. Sequence data of two other genome regions, namely the β-tubulin and EF1-α gene and intron regions, were combined with ITS rDNA sequence data to determine the phylogenetic relationship between these isolates. Isolates of B. lutea and those from Australian Acacia species were not significantly different in spore morphology. The yellow pigment, however, was much more distinct in cultures of B. lutea than in cultures from Acacia. There were only a few base pair variations in each of the analyzed gene regions, but these variations were fixed in the two groups in all regions. By combining these data it was clear that B. lutea and the isolates from Acacia were distinct species, albeit very closely related. We, therefore, propose the new epithet B. australis for the fungus from Australia. Botryosphaeria australis also was isolated in this study from exotic Sequoiadendron trees in Australia. Re-analyses of GenBank data in this study showed that B. australis also occurs on other native Australian hosts, namely a Banksia sp. and a Eucalyptus sp., as well as a native Protea sp. in South Africa and on Pistachio in Italy. These records from GenBank have been identified previously as B. lutea. The common occurrence of B. australis on a variety of native hosts across Australia suggests that this fungus is native to this area.  相似文献   

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