Showing papers by "Michael J. Wingfield published in 1999"
TL;DR: A PCR-restriction fragment length polymorphism technique is developed that reliably distinguishes F. pini from other isolates identified as F. subglutinans from the other biological species in the G. fujikuroi species complex.
Abstract: 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.
122 citations
TL;DR: It is concluded that fertile F. 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.
Abstract: 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.
101 citations
TL;DR: The data strongly suggest that both the South African and Australian P. cinnamomi populations are introduced, with relatively high levels of genetic differentiation between mating type populations providing evidence for the lack of frequent sexual reproduction in both populations.
Abstract: Phytophthora cinnamomiisolates from South Africa and Australia were compared to assess genetic differentiation between the two populations. These two populations were analysed for levels of phenotypic diversity using random amplified polymorphic DNAs (RAPDs) and gene and genotypic diversity using restriction fragment length polymorphisms (RFLPs). Sixteen RAPD markers from four decanucleotide Operon primers and 34 RFLP alleles from 15 putative loci were used. A few isolates from Papua New Guinea known to posses alleles different from Australian isolates were also included for comparative purposes. South African and Australian P. cinnamomipopulations were almost identical with an extremely low level of genetic distance between them (DmD 0:003). Common features for the two populations include shared alleles, low levels of phenotypic/genotypic diversity, high clonality, and low observed and expected levels of heterozygosity. Furthermore, relatively high levels of genetic differentiation between mating type populations (Dm South AfricaD 0:020 andDm AustraliaD 0:025 respectively), negative fixation indices, and significant deviations from Hardy‐Weinberg equilibrium, all provided evidence for the lack of frequent sexual reproduction in both populations. The data strongly suggest that both the South African and Australian P. cinnamomipopulations are introduced.
74 citations
TL;DR: In this article, Cylindrocladium candelabrum-like isolates were collected from a wide variety of geographic lo- cations and compared based on their morphology, sexual compatibility and the nucleotide sequences of their rDNA ITS regions.
Abstract: Cylindrocladium candelabrum-like isolates were collected from a wide variety of geographic lo- cations and compared based on their morphology, sexual compatibility and the nucleotide sequences of their rDNA ITS regions. All isolates included in this study mated to produce Calonectria teleomorphs with viable progeny. Four distinct mating populations were identified, each representing a genetically iso- lated, biallelic, heterothallic population. Several rep- resentative isolates of each mating population, re- flecting geographic diversity, were chosen for se- quence comparisons. The internal transcribed spacer (ITS) regions 1 and 2 that flank the 5.8S rDNA gene, as well as the gene itself, were sequenced and com- pared. All isolates representing the same group yield- ed similar sequences, but small, consistent differenc- es were found between the groups. Based on these results we recognise Calonectria scoparia (anamorph Cylindrocladium candelabrum), and describe three new species, namely Calonectria pauciramosa (ana- morph Cylindrocladium pauciramosum), Calonectria insularis (anamorph Cylindrocladium insularae) and Calonectria mexicana (anamorph Cylindrocladium mexicanum).
63 citations
TL;DR: In this article, the authors determined the phylogenetic relationships among strains of C. cubensis, which causes a serious canker disease of Eucalyptus in many tropical areas of the world.
Abstract: Cryphonectria cubensis causes a serious canker disease of Eucalyptus in many tropical areas of the world. The aim of this study was to determine the phylogenetic relationships among strains of C. c...
56 citations
01 Jan 1999
TL;DR: The aim of this study was to determine the phylogenetic relationships among strains of C. c.
Abstract: Cryphonectria cubensis causes a serious can- ker disease of Eucalyptus in many tropical areas of the world. The aim of this study was to determine the phylogenetic relationships among strains of C. cub- ensis and the related species C. parasitica, Endothia eugeniae and E. gyrosa using DNA sequence data. A second objective was to develop a rapid diagnostic method to distinguish among these taxa. The vari- able ITS1 and ITS2 regions, as well as the conserved 5.8S gene of the rRNA operon, were amplified and sequenced. The amplified PCR products were also used in Alu I and Cfo I restriction digests. Analysis of the restriction profiles indicate that it is possible to distinguish between C. cubensis, C. parasitica, E. eu- geniae and E. gyrosa using RFLPs (restriction frag- ment length polymorphisms). This will facilitate the identification of isolates thought to represent C. cub- ensis that sporulate poorly in culture. Analysis of the sequence data showed that C. cubensis isolates form a distinct clade that includes a strain from clove that might otherwise have been assigned the name E. eu- geniae. Isolates of C. parasitica formed a separate clade. Endothia gyrosa grouped separately from both C. cubensis and C. parasitica.
53 citations
TL;DR: A rapid and reliable PCR-based RFLP identification method is developed and phylogenetic relationships among the betterknown species of Ceratocystis are considered to form a sound foundation for further taxonomic studies of the group.
48 citations
TL;DR: Five ophiostomatoid taxa have been found associated with the infructescences of Protea species, an ancient group of flowering plants endemic to South Africa, and two of these fungi are characterized by their unusual Knoxdavesia anamorphs and have been placed in Gondwanamyces.
32 citations
TL;DR: The capacity of wounds to close through callus production was correlated with the relative susceptibility of these clones to infection by C. cubensis, and those with a lower capacity to close wounds were most susceptible to Cryphonectria canker.
Abstract: Summary
Twenty-five different Eucalyptus grandis clones were artificially wounded and inoculated with a virulent isolate of Cryphonectria cubensis. The capacity of wounds to close through callus production was correlated with the relative susceptibility of these clones to infection by C. cubensis. Clones with the greatest capacity to close wounds were those that were also most tolerant to C. cubensis infection. Those with a lower capacity to close wounds were most susceptible to Cryphonectria canker.
30 citations
TL;DR: Considerable variation was, however, noticed between individual trees within the same family and the incorporation of disease tolerant trees into breeding programmes is proposed.
Abstract: Ceratocystis albofundus is a recently described pathogen infectingAcacia mearnsii in South Africa, and it causes a disease known as Ceratocystis wilt. Symptoms of the disease include die-back, gummosis and wilting of infected trees. In order to select trees tolerant to this fungus, susceptibility tests were conducted on trees representing fourteen families ofA. mearnsii. A virulent isolate ofC. albofundus was selected and inoculated into the stems of twelve-month-old plants in a plantation. Lesion lengths, in the bark, and disease development were assessed after 6 weeks. All fourteen families ofA. mearnsii were susceptible to infection byC. albofundus. Considerable variation was, however, noticed between individual trees within the same family and the incorporation of disease tolerant trees into breeding programmes is proposed.
28 citations
TL;DR: Based on its bitunicate asci, as well as pseudothecial and ascospore morphology, a new combination for P proteae is proposed in Botryos- phaeria, as B. proteae.
Abstract: Phyllachora proteae is a well known leaf pathogen of Protea spp. In the present study this fun- gus was recollected from several genera and species of Proteaceae in the Western Cape province of South Africa, and its taxonomy was reassessed. Single asco- spore cultures produced a Fusicoccum anamorph in culture, described here as F proteae. A microconidial synanamorph with narrowly ellipsoidal, brown, thick- walled conidia was commonly associated with F pro- teae in culture. Based on its bitunicate asci, as well as pseudothecial and ascospore morphology, a new combination for P proteae is proposed in Botryos- phaeria, as B. proteae.
TL;DR: Results of this study provide valuable information on selection of P. cinnamomi isolates for future resistance/tolerance screening assays of Eucalyptus germplasm in South Africa.
Abstract: Phytophthora cinnamomi isolates from South Africa were evaluated for differences in growth rate in vitro and levels of pathogenicity towards Eucalyptus smithii in the field. Inoculations were conducted in the field in summer and winter in two subsequent years at two locations in South Africa using 59 P. cinnamomi isolates. The isolates differed significantly in growth rate in vitro, as well as in levels of pathogenicity to E. smithii in the field. Growth rate in vitro was significantly influenced by interactions with culture age, geographic origin and genetic background as determined using isozymes. Levels of pathogenicity in the field were influenced by season of inoculation and average minimum temperatures at trial sites. The host from which P. cinnamomi isolates were originally obtained did not significantly affect levels of pathogenicity in the field. Culture age had a significant negative effect on growth rate in vitro and pathogenicity in the field. Significant differences in levels of pathogenicity could be found for different multilocus isozyme genotypes. Geographic origin and mating type of P. cinnamomi isolates had no significant effect on levels of pathogenicity in the field. A positive correlation was found between growth rate in vitro and levels of pathogenicity in the field. Levels of variation for pathogenicity within A1 mating type isolates were significantly lower than for A2 mating type isolates. Results of this study provide valuable information on selection of P. cinnamomi isolates for future resistance/tolerance screening assays of Eucalyptus germplasm in South Africa.
TL;DR: Results suggest that species of Gondwanamyces and C. olivaceae are phylogenetically related and have a shared ancestry, and that Gondwanaamyces is probably not a teleomorph for Custingophora oliv Families.
TL;DR: The vascular wilt pathogen currently causing severe die-back and mortality of takamaka in the Seychelles has morphological and physiological characters inconsistent with its placement in Verticillium so Leptographium calophylli comb.
TL;DR: Batcheloromyces spp.
Journal Article•
TL;DR: Phyllachora proteae was recollected from several genera and species of Proteaceae in the Western Cape of South Africa, and its taxonomy was reassessed.
Abstract: Phyllachora proteae is a \\\\'ell knO\\\\'n leaf pathogen of Pro/ea spp. In the present study this fungus \\..'as recollected from several genera and species of Proteaceae in the \\Vestern Cape prO\\'ince of South Africa, and its taxonomy was reassessed. Single ascospore cultures produced a Fusicoccu m anamorph in culture, described here as F pTOteae, .-\\ microconidial synanamorph with narrowly ellipsoidal. brown. thickwalled conidia was commonly associated \\\\ith F pro¥ teae in culture, Based on its bitunicate asci. as \\\\'ell as pseudothecial and ascospore morphology. a ne\\\\! combination for P proteae is proposed in Botryosphaeria, as B. proteae, Key JVords: BotT};Osphaeria, Fusicoccum. Protea. systematics
01 Jan 1999
TL;DR: A recent collection of diseased leaf material from eucalypt plantations in Queensland (Qld) revealed the existence of a Mycosphaerella species, with a Dissoconium anamorph, previously not recorded in Australia.
Abstract: Dissoconium is an anamorph genus associated with the teleomorph taxon Mycosphaerella. In Australia, Mycosphaerella species cause significant levels of disease in eucalypt plantations. A recent collection of diseased leaf material from eucalypt plantations in Queensland (Qld) revealed the existence of a Mycosphaerella species, with a Dissoconium anamorph, previously not recorded in Australia.