Fusarium subglutinans f. sp. Pini represents a distinct mating population in the gibberella fujikuroi species complex

Fusarium strains in the Gibberella fujikuroi species complex cause diseases on a variety of economically important plants. One of these diseases, pitch canker of Pinus spp., is caused by strains identified as Fusarium subglutinans f. sp. pini. Fertile crosses were detected between F. subglutinans f. sp. pini strains from South Africa, California, and Florida. F. subglutinans f. sp. pini strains were not cross-fertile with the standard tester strains of six of the seven other mating populations of G. fujikuroi. Sporadic perithecia with ascospores were obtained in two crosses with the mating population B tester strains. These perithecia were homothallic, and the ascospores derived from these perithecia were vegetatively compatible with the mating population B tester strain parent. We concluded that fertile F. subglutinans f. sp. pini isolates represent a new mating population (mating population H) of G. fujikuroi and that they belong to a unique biological species in a distinct taxon.     

Characterization of Fusarium spp. associated with pineapple fruit rot and leaf spot in Peninsular Malaysia

Pineapple (Ananas comosus) is one the important fruit crops planted in Malaysia, and this study was conducted to determine Fusarium spp. associated with diseases of the fruit crop as Fusarium is prevalent in tropical countries. Our objective was to identify and characterize Fusarium spp. associated with pineapple fruit rot and leaf spot mainly found on the fruits and leaves in Peninsular Malaysia. Fusarium isolates (n = 108) associated with pineapple fruit rot and leaf spot were characterized by morphological, molecular and phylogenetic analyses, a mating study and pathogenicity testing. TEF‐1α sequence analysis identified Fusarium proliferatum, Fusarium verticillioides, Fusarium sacchari and Fusarium sp. Mating was successful only between tester strains of F. proliferatum and F. verticillioides. Sexual crosses with standard tester strains showed that 82 isolates of F. proliferatum produced fertile crosses with mating population D (Gibberella intermedia) and three isolates of F. verticillioides were fertile with the tester strain of mating population A (Gibberella moniliformis). All isolates were pathogenic, causing pineapple fruit rot and leaf spot, thus fulfilling Koch's postulates.     

New species of Gondwanamyces from dying Euphorbia trees in South Africa

Gondwanamyces and its Custingophora anamorphs were first described from Protea infructescences in South Africa. Subsequently these unusual fungi were also found on Cecropia in Central America. During an investigation into the decline and death of native Euphorbia trees in South Africa, several fungal isolates resembling the anamorph state of Gondwanamyces were obtained from diseased tissues. In this study these isolates are identified based on morphology and comparisons of DNA sequences. Two previously unknown Gondwanamyces species were identified, both were associated with damage caused by beetles (Cossonus sp.). Inoculation studies showed that the new species of Gondwanamyces are pathogenic on Euphorbia ingens and may contribute to the decline of these trees.     

Differentiation of Fusarium subglutinans f. sp. pini by histone gene sequence data.

Fusarium subglutinans f. sp. pini (= F. circinatum) is a pathogen of pine and is one of eight mating populations (i.e., biological species) in the Gibberella fujikuroi species complex. This species complex includes F. thapsinum, F. moniliforme (= F. verticillioides), F. nygamai, and F. proliferatum, as well as F. subglutinans associated with sugarcane, maize, mango, and pineapple. Differentiating these forms of F. subglutinans usually requires pathogenicity tests, which are often time-consuming and inconclusive. Our objective was to develop a technique to differentiate isolates of F. subglutinans f. sp. pini from other isolates identified as F. subglutinans. We sequenced the histone H3 gene from a representative set of Fusarium isolates. The H3 gene sequence was conserved and contained two introns in all the isolates studied. From both the intron and the exon sequence data, we developed a PCR-restriction fragment length polymorphism technique that reliably distinguishes F. subglutinans f. sp. pini from the other biological species in the G. fujikuroi species complex.     

APERTURE EVOLUTION IN THE GENUS PTYCHOPETALUM BENTH. (OLACACEAE)

The genus Ptychopetulum (Olacaceae), disjunct between South America (2 spp.) and Africa (2 spp. West Africa; I sp. Rhodesia), exhibits predominantly diploporate pollen among the West African species and predominantly triporate pollen among the South American taxa. An analysis of aperture evolution suggests two possible schemes of aperture evolution for the genus. Scheme I avers the independent origin of both triporate and diploporate apertures from a basic brevicolpate condition while scheme II proposes a basic diploporate condition in which the diploporate apertures have migrated to the equator, fused to form brevicolpi and have ultimately become reduced to pores. Pollen evidence in support of both schemes is discussed. The distribution of aperture types within the genus also suggests West Africa as the original site of aperture evolution and South America as the second area of aperture development with types traceable to West African stock.     

Botryosphaeriaceae as potential pathogens of prunus species in South Africa, with descriptions of Diplodia africana and Lasiodiplodia plurivora sp. nov

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.     

Molecular phylogenetic analyses reveal three new Ceratocystis species and provide evidence for geographic differentiation of the genus in Africa

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.     

Ectoparasitic adaptations in Forcipomyia from butterflies with two new African species (Ceratopogonidae)

Abstract. Two new ectoparasities of butterflies from Africa are described: Forcipomyia (Trichohelea) monoplectron sp.n. and F.collinsi sp.n. A key for the identification of the African species ofthe subgenus Trichohelea is given. The extraodinary distribution of F.collinsi in Africa and South America is tentatively correlated with the distribution of migratory Rhopalocera. An hypothesis is presented for the functional significance of the tarsal claw modifications in this group of parasites.     

香蕉上的镰孢菌种类及其系统发育关系(英文)

镰孢菌属真菌是香蕉上的重要病原菌,主要引起香蕉枯萎病以及香蕉冠腐病,在我国已明确引起香蕉枯萎病的病原为尖孢镰孢古巴专化型 Fusarium oxysporum f. sp. cubense(FOC)1号和4号生理小种,但是引起香蕉冠腐病的镰孢菌种类还未明确。为了解香蕉上镰孢菌在种间及种内水平上的多样性,2008–2011 年间作者从华南地区不同的水果市场及香蕉果园采集香蕉样品90份,分离得到143株镰孢菌。通过形态学观察及基于 EF-1α基因的系统进化分析鉴定出10种镰孢菌,即F. oxysporum、F. solani、F. camptoceras、F. pallidoroseum、F. stiloides、F. chlamydosporum、F.verticillioides、F. proliferatum、F. concentricum、F. sacchari,以及藤仓赤霉复合种(Gibberella fujikuroi species complex,GFC)中 3 个未定名的类群。轮纹镰孢 F. concentricum 及甘蔗镰孢 F.sacchari 是香蕉果实中最常见种,前菌为我国首次报道,后菌是首次报道与香蕉有关。对从香蕉上分离的藤仓赤霉复合种(GFC)及尖孢镰孢复合种(FOSC)的EF-1α序列进行了系统发育分析,其GFC中的27个菌株组成的单系群可分为7个不同的亚群,分别为 F.verticillioides、F. proliferatum、F. concentricum、F. sacchari 以及3个没有描述过的菌系 Fusarium sp. 1、Fusarium sp.2和 Fusarium sp.3;FOSC中的50个菌株形成2大分枝共12个谱系,分离自我国华南地区的21株尖孢镰孢形成7个谱系,其中 13株已知的香蕉枯萎病病原菌分布在3个谱系中,我国大陆的香蕉枯萎病病原菌菌株与来源于台湾地区及东南亚的菌株亲缘关系较近,FOC1号生理小种的遗传分化大于4号生理小种,FOC 1号生理小种与分离自香蕉果实上的尖孢镰孢菌的亲缘关系比与FOC 4号生理小种的亲缘关系更近。研究结果表明,我国香蕉上存在着丰富的镰孢菌种类,而且种内遗传多样性丰富。     

First Report of Stem Canker on Phoenix Tree (Firmiana simplex) Caused by Fusarium oxysporum in China

A stem canker disease was observed on the phoenix trees located in the region of Dezhou, Shandong province. Symptomatic stems were collected and evaluated for the possible casual agent of the disease. A fungus resembling Fusarium sp. was consistently isolated from pieces of symptomatic tissues. The fungus formed abundant aerial mycelium on potato dextrose agar and produced the micro‐ and macro‐conidia on carnation leaf agar. The nucleotide sequences of the internal transcribed spacer of the rDNA from three representative isolates showed 100% identical to those of Fusarium oxysporum isolates deposited in the GenBank database. On the basis of morphological characteristics, pathogenicity test and molecular identification, the causal agent was identified as F. oxysporum. To our knowledge, this is the first report of stem canker on phoenix tree caused by F. oxysporum in China.     

Pathogenicity of Fusarium oxysporum Isolates from Malaysia and F. oxysporuin f. sp. elaeidis from Africa to Seedlings of Oil Palms (Elaeis guineensis)

Pathogenicity tests with Fusarium oxysporum isolated form Malaysian oil palm were made with oil palms seedlings raised form Malaysian seed as well s with wilt-susceptible seedlings gown from African seed. Oil palm seedlings grown form Malaysian seed were also inoculated with African isolates of F. oxysporum f. sp. elaeidis and F. oxysporum var. redolens. The experiments were made under normal soil moisture conditions and under water stress. F. oxysporum f. sp. elaeidis isolates form Africa were pathogenic to oil palm seedlings from Malaysian seeds but the Malaysian F oxysporum isolates were non-pathogenic to plams grown from Malaysian seed or the wilt-susceptible palms from African seed. Seedlings from Malaysian seed proved to be highly susceptible to the vascular wilt disease caused by F. oxysporum f. sp. elaeidis as 75–90% of the palms were infected. The susceptibility of the palms from Malaysian seed varied with different African isolates tested. The Yaligimba isolate from Zaire which was found to be F. oxysporum var. redolens was the most virulent. Disease was more severe when oil palm seedlings were subjected to a period of water stress. The incidence of death in the seedlings under stress conditions was 45% as compared with only 15% for palms grown under normal conditions.     

Colonization of barley roots by endophytic fungi and their reduction of take-all caused by Gaeumannomyces graminis var. tritici

Fungal root endophytes obtained from natural vegetation were tested for antifungal activity in dual culture tests against the root pathogen Gaeumannomyces graminis var. tritici. Fifteen isolates, including Acremonium blochii, Acremonium furcatum, Aspergillus fumigatus, Cylindrocarpon sp., Cylindrocarpon destructans, Dactylaria sp., Fusarium equiseti, Phoma herbarum, Phoma leveillei, and a sterile mycelium, selected based on the dual culture test, were inoculated on barley roots in growth tubes under axenic conditions, both in the absence and presence of G. graminis var. tritici. All isolates colonized the rhizosphere and very often the root cortex without causing disease symptoms and without affecting plant growth. Eight isolates significantly reduced the symptoms caused by G. graminis var. tritici, and 6 of them reduced its presence in the roots.     

Sudden-death syndrome of soybean is caused by two morphologically and phylogenetically distinct species within the Fusarium solani species complex--F. virguliforme in North America and F. tucumaniae in South America

Soybean sudden-death syndrome has become a serious constraint to commercial production of this crop in North and South America during the past decade. To assess whether the primary etiological agent is panmictic in both hemispheres, morphological and molecular phylogenetic analyses were conducted on strains selected to represent the known pathogenic and genetic diversity of this pathogen. Maximum-parsimony analysis of DNA sequences from the nuclear ribosomal intergenic spacer region and the single copy nuclear gene translation elongation factor 1-α, together with detailed morphological comparisons of conidial features, indicate that SDS of soybean in North and South America is caused by two phylogenetically and morphologically distinct species. Fusarium virguliforme sp. nov., formally known as F. solani f. sp. glycines, is described and illustrated for the SDS pathogen in North America, and F. tucumaniae sp. nov. is proposed for the South American pathogen. The molecular phylogenetic results challenge the forma specialis naming system because pathogenicity to soybean might have evolved convergently in F. tucumaniae and F. virguliforme. Phylogenetic evidence indicates the two SDS pathogens do not share a most recent common ancestor, since F. tucumaniae was resolved as a sister to a pathogen of Phaseolus vulgaris, F. phaseoli comb. nov. All three pathogens appear to have evolutionary origins in the southern hemisphere since they are deeply nested within a South American clade of the F. solani species complex.     

A PCR-denaturing gradient gel electrophoresis approach to assess Fusarium diversity in asparagus

In North America, asparagus (Asparagus officinalis) production suffers from a crown and root rot disease mainly caused by Fusarium oxysporum f. sp. asparagi and F. proliferatum. Many other Fusarium species are also found in asparagus fields, whereas accurate detection and identification of these organisms, especially when processing numerous samples, is usually difficult and time consuming. In this study, a PCR-denaturing gradient gel electrophoresis (DGGE) method was developed to assess Fusarium species diversity in asparagus plant samples. Fusarium-specific PCR primers targeting a partial region of the translation elongation factor-1 alpha (EF-1 alpha) gene were designed, and their specificity was tested against genomic DNA extracted from a large collection of closely and distantly related organisms isolated from multiple environments. Amplicons of 450 bp were obtained from all Fusarium isolates, while no PCR product was obtained from non-Fusarium organisms. The ability of DGGE to discriminate between Fusarium taxa was tested over 19 different Fusarium species represented by 39 isolates, including most species previously reported from asparagus fields worldwide. The technique was effective to visually discriminate between the majority of Fusarium species and/or isolates tested in pure culture, while a further sequencing step permitted to distinguish between the few species showing similar migration patterns. Total genomic DNA was extracted from field-grown asparagus plants naturally infested with different Fusarium species, submitted to PCR amplification, DGGE analysis and sequencing. The two to four bands observed for each plant sample were all affiliated with F. oxysporum, F. proliferatum or F. solani, clearly supporting the reliability, sensitivity and specificity of this approach for the study of Fusarium diversity from asparagus plants samples.     

Trypanosoma vivax: characterization of the spliced-leader gene of a Brazilian stock and species-specific detection by PCR amplification of an intergenic spacer sequence.

The sequence of the spliced-leader gene repeat of a Brazilian Trypanosoma vivax stock from cattle showed high similarity to sequences of West African T. vivax in both intron and intergenic sequences. This is the first evidence based on DNA sequences of close-relatedness between Brazilian and West African T. vivax stocks. A T. vivax-specific diagnostic PCR assay based on spliced-leader gene intergenic sequences was able to amplify DNA from T. vivax stocks from South America (Brazil, Bolivia, and Colombia) and West Africa. Species-specificity of this method was confirmed by results obtained by testing 15 other trypanosomes, including other species and subspecies that can also infect cattle. The PCR assay developed presented high sensitivity, detecting the DNA content of only one parasite and also revealing T. vivax infection in asymptomatic animals without detectable parasitemia by microhematocrit or in Giemsa-stained blood smears. Use of crude preparations from field-blood samples collected on both filter paper and glass slides as DNA template suggested that this method could be useful for the diagnosis of T. vivax in large epidemiological studies.     

Pathogenicity and Host Specificity of Mycovellosiella lantanae var. lantanae,a Potential Biocontrol Agent for Lantana camara in South Africa

Lantana camara is a poisonous, bushy shrub from South and Central America that has invaded much of the moist, warm sub-tropical areas of South Africa. In the last decade, evidence of a conspicuous and damaging mycobiota on lantana in the Neotropics has persuaded biocontrol researchers to consider fungi as potential biocontrol agents for this plant. Samples of diseased L. camara leaves were collected during field surveys in South, North and Central America from 1987 to 1997. Pathogenicity tests showed the leaf spot fungus, Mycovellosiella lantanae var. lantanae to be a promising biocontrol pathogen. Inoculations onto South African biotypes of L. camara and a number of closely related species within the family Verbenaceae were made under quarantine conditions to determine the pathogenicity and host specificity of the fungus. Inoculation of L. camara biotypes resulted in necrotic, grey lesions (20-60 per leaf), necrosis of flower buds and stalks, as well as defoliation of certain biotypes after three weeks. None of the other plant species tested showed any disease symptoms. This indicates a very restricted host range, making this pathogen a suitable candidate for application as a biological control agent. It is expected that the fungus will reduce the vigour and reproductive potential of L. camara. Due to the variation in virulence of M. lantanae var. lantanae when tested on South African lantana biotypes, release strategies may include the use of combinations of the isolates to target a wider range of lantana biotypes in the field. Permission to release M. lantanae var. lantanae in South Africa was granted in September 2001. The pathogen will be released as a classical biocontrol agent in South Africa.     

Botrytis caroliniana, a new species isolated from blackberry in South Carolina

Blackberry fruits symptomatic for gray mold were collected from three commercial blackberry fields in northwestern South Carolina. Single-spore isolates were generated and two distinct phenotypes were discovered in each location; one sporulated on PDA and one did not. One isolate of each phenotype and location (six isolates total) were selected for in depth molecular and morphological characterization. Glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60) and DNA-dependent RNA polymerase subunit II (RPB2) coding sequence alignment revealed Botrytis cinerea as the sporulating phenotype and a new yet undescribed species as the non-sporulating phenotype. The new Botrytis sp., described herein as Botrytis caroliniana, was most closely related genetically to B. fabiopsis and B. galanthina, the causal agents of gray mold disease of broad bean and snowdrop, respectively. It produces smaller conidia than either B. fabiopsis or B. galanthina, and sequence analysis of genes encoding necrosis and ethylene-inducing proteins (NEPs) also indicated that the Botrytis isolates represent a separate and distinct species. The new species is pathogenic on blackberry fruits and broad bean leaves, which distinguishes it further from B. galanthina. The new species formed white to pale gray colonies with short, tufted aerial mycelium and produced black sclerotia on PDA at 20 C. To our knowledge this is only the third Botrytis species discovered to cause disease on blackberry in the United States.     

The Afro-American Biomphalariae

The reports on the occurrence of African planorbids in South America and of South American species in Africa and Asia are reviewed.     

Comments on the gonotyl of Proctocaecum macroclemidis (Tkach and Snyder, 2003) n. comb. (Digenea: Acanthostomidae: Acanthostominae), with a key to the genera of acanthostominae and new phylogenetic tree for Proctocaecum Baugh, 1957

The species recently described as Acanthostomum macroclemidis possesses the gonotyl in the form of a solid muscular pad uniquely diagnostic for species of Proctocaecum and is accordingly transferred to that genus. An artificial key to the 5 acanthostomine genera, as well as an updated phylogenetic hypothesis for the 10 known species of Proctocaecum, based on 11 characters and including 2 species described since the last phylogenetic analysis, are presented. The single most parsimonious phylogenetic tree with a consistency index of 87.5% suggests that Proctocaecum originated in Africa and spread to North America and South America before the breakup of Pangaea. As a result, the 2 North American and 1 South American species are most closely related to different African members of the genus. African and Indo-Pacific species inhabit crocodylids; hence, the occurrence of North American species in alligatorids and chelonians and a South American species in alligatorids are the result of host switches.