Diagnostic markers for Teratosphaeria destructans and closely related species

Teratosphaeria foliar pathogens cause leaf and shoot blight on Eucalyptus trees in many parts of the world. Among them, T. destructans is one of the most aggressive pathogens causing defoliation of young Eucalyptus trees in tropic regions. Identification of T. destructans to species level is currently not possible based solely on morphological characteristics or ITS sequence data. The aim of this study was to assess T. destructans microsatellites and a newly developed T. epicoccoides microsatellite as a diagnostic tool to differentiate among T. destructans and several closely related foliar pathogens. Based on the number of markers that amplified, the T. destructans microsatellites allowed for the differentiation of T. destructans, T. epicoccoides,T. eucalypti,T. nubilosa,T. pseudoeucalypti and T. viscidus. These microsatellites provide a rapid and cost-effective diagnostic tool that will enable the identification of a large number of isolates important in disease surveys and inoculation trials.Supplementary material: Table S1. Teratosphaeria isolates and their sequences used for phylogenetic analyses.Table S2. Microsatellite markers and panel designs for Teratosphaeria species.Table S3. BLASTn results of microsatellites in the Teratosphaeria genomes.The National Research Foundation, the SARChI Chair in Fungal Genomics, the UP Doctoral Research Bursary and the Tree Protection Co-operative program (TPCP).http://wileyonlinelibrary.com/journal/efp2021-10-27hj2021BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

Genetic recombination in Teratosphaeria destructans causing a new disease outbreak in Malaysia

The Eucalyptus foliar pathogen Teratosphaeria destructans causes severe and widespread damage in South-East Asian and South African plantations. In 2016, leaf blight symptoms resembling those caused by T. destructans were observed in a plantation of a Eucalyptus grandis × E. urophylla hybrid in Sabah, Malaysia. The aims of this study were to confirm the identity of the causal agent as T. destructans and to investigate the genetic structure of isolates associated with this newly detected disease outbreak. Using sequence data of three gene regions, the identity of the pathogen was confirmed as T. destructans. The mating type and microsatellite genotypes of 41 isolates from this Malaysian population were identified and compared with those from previously characterized populations in South-East Asia and South Africa. The Malaysian population had the highest genotypic diversity of any T. destructans population thus far investigated. Both the mating types were found in the collection of isolates, and these were in approximately equal proportions. Although structures linked to a sexual state of the fungus have not been found, sexual reproduction is theoretically possible and could explain the high genetic diversity in the pathogen that must have been accidentally introduced into Malaysia. This is the first record of T. destructans in Sabah and, to the best of our knowledge, in also other parts of Borneo.The SARChI chair in Fungal Genomics; South African Agency for Science and Technology Advancement, Grant/Award Number: - NRF Centre of Excellence in Tree Health Biotechn; Tree Protection Co- operative program (TPCP); University of Pretoria (UP) Doctoral Research Bursary; National Research Foundation.http://www.wileyonlinelibrary.com/journal/efphj2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

Genetic diversity of Teratosphaeria pseudoeucalypti in Eucalyptus plantations in Australia and Uruguay

Please read abstract in the article.http://link.springer.com/journal/133132022-06-16hj2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

The phylogenetic significance of leaf anatomical traits of southern African oxalis

CITATION: Jooste, M., Dreyer, L. L. & Oberlander, K. C. 2016. The phylogenetic significance of leaf anatomical traits of southern African oxalis. BMC Evolutionary Biology, 16:225, doi:10.1186/s12862-016-0792-z.The original publication is available at https://bmcevolbiol.biomedcentral.comPublication of this article was funded by the Stellenbosch University Open Access Fund.Background: The southern African Oxalis radiation is extremely morphologically variable. Despite recent progress in the phylogenetics of the genus, there are few morphological synapomorphies supporting DNA-based clades. Leaflet anatomy can provide an understudied and potentially valuable source of information on the evolutionary history and systematics of this lineage. Fifty-nine leaflet anatomical traits of 109 southern African Oxalis species were assessed in search of phylogenetically significant characters that delineate clades. Results: A combination of 6 leaflet anatomical traits (stomatal position, adaxial epidermal cells, abaxial epidermal cells, mesophyll, sheath around vascular tissue, degree of leaflet conduplication) clearly support various clades defined by previous DNA-based phylogenetic work. Other, mostly continuous leaflet anatomical traits were highly variable and showed less phylogenetic pattern. Conclusions: Major and unexpected findings include the transition from ancestral hypostomatic leaflets to adaxially-located stomata in the vast majority of southern African Oxalis, the loss of semi-swollen AB epidermal cells and the gain of swollen adaxial and abaxial epidermal cells in selected clades, and multiple changes from ancestral bifacial mesophyll to isobilateral or homogenous mesophyll types. The information gathered in this study will aid in the taxonomic revision of this speciose member of the Greater Cape Floristic Region and provide a basis for future hypotheses regarding its radiation.https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-016-0792-zPublisher's versio

Monitoring the success of an old-field rehabilitation trial in the winter rainfall succulent Karoo : the effect of Oxalis pes-caprae

Thesis (MSc (Conservation Ecology)--University of Stellenbosch, 2004.89 leaves single sided printed, preliminary pages i-xiv and numbered pages 1-89. Includes bibliography. List of tables, figures used.Scanned with a Hp Scanjet 8250 Scanner to pdf format (OCR).ENGLISH ABSTRACT: The main aim of an old field rehabilitation trial initiated in 2000 was to find a solution to the rehabilitation process for approximately 90 000 ha of unutilised land in the Little Karoo, South Africa. Depending only on a natural succession process to restore unutilised old fields would mean that the period of recovery would be longer than the life span of an average farmer. The trial, initiated by Witbooi in 2000 aimed to see how human intervention can facilitate the process of rehabilitation of old-fields. Three years later, the trial was again monitored to evaluate the success of reseeded indigenous species and method of cultivation in the rehabilitation process. A second objective was based on a result of Witbooi (2002) who showed that there was a tendency of 0. pes-caprae to invade disturbed areas, and aimed to evaluate the effect of this species on the rehabilitation process. Seven indigenous species were reseeded in 2000, of which only four species germinated and survived to the present. These surviving species are Pteronia incana Burm Dc., Tripteris sinuata DC., Ehrharta calycina SM and Chaetobromus dregeanus Nees. The highest level of recruitment in 2001 was recorded for T sinuata followed by P. incana, E. calycina and C. dregeanus. In September 2003, three years after the trial was initiated, the highest number of surviving seedlings were of T sinuata followed by E. calycina, C. dregeanus and P. incana. Five different cultivation methods were used to enhance the germination rate and survival of seedlings. The number of seedlings that survived differs according to the cultivation methods and soil type. Tripteris sinuata had the highest number of surviving seedlings in all cultivation methods off-heuweltjies. Tripteris sinuata was therefore selected to analyse the effect of various cultivation methods. The second objective was to study the impact of Oxalis pes-caprae on species diversity in restored old fields by assessing its ability to disperse in old fields under different cultivation methods. The multivariate ANOVA results showed that there was a significant difference in the density of O. pes-caprae between on and off heuweltjies (sites) and treatments (cultivation methods). There was a significant difference in the density of O. pes-caprae between cultivation methods. A Post Hoc LSD test showed a significant difference in the density of aboveground O. pes-caprae plants between control sites (no disturbance) compared to those sites that underwent some sort of soil disturbance. There was, however, no significant difference in the abundance of O. pes-caprae on plots that underwent some sort of disturbance (i.e Cleared vs Tilled vs Disked vs Ploughed sites) on heuweltjies. There was a significant difference in the number of O. pes-caprae bulbs collected between blocks (on and off-heuweltjie) and significant differences between cultivation methods. There was also a significant difference in bulb diameter between cultivation methods when compared between on and off-heuweltjie sites. The bulbs were classified into four measurement classes. The highest number of small (2-5 mm diameter) and medium (5-8 mm diameter) sized bulbs were found in the Tilled cultivation method. In contrast the Control treatment (uncultivated) had the highest number of large sized bulbs (14-17 mm diameter) and medium bulbs size categories. In conclusion, T. sinuafa has the potential to be used for rehabilitation of old fields in combination with Tilled cultivation method. Attention should be paid to the effect of O. pes-caprae especially on heuweltjies where this species showed a complete dominance in the rehabilitation trial.AFRIKAANSE OPSOMMING: Die hoof doel van 'n ou veld rehabilitasie eksperiment wat in 2000 geinisieer is was om 'n oplossing te vind vir die rehabilitasie proses vir ongeveer 90 000 ha onbenutte land in die Klein Karoo, Suid-Afrika. Indien daar slegs op natuurlike suksessie prosesse staatgemaak word om die onbenutte ou lande te restoreer, sou dit beteken dat die periode van herstel langer sou wees as die lewensverwagting van die gemiddelde boer. Hierdie eksperiment, wat in 2000 deur Witbooi geinisieer is, het gepoog om te bepaal hoe menslike inmenging die proses van rehabilitasie van ou velde kan fasiliteer. Drie jaar later is die eksperiment weer gemonitor om die sukses van die teruggesaaide inheemse spesies en bewerkings-metodes in die rehabilitasie proses te evalueer. 'n Tweede doelwit is gebaseer op 'n resultaat van Witbooi (2002) wat aangetoon het dat daar 'n neiging was vir O. pes-caprae om versteurde areas binne te dring, en het dus gemik om die effek van hierdie spesie op die rehabilitasie proses te evalueer. Sewe inheemse spesies is in 2000 teruggesaai, waarvan slegs 4 spesies ontkiem en oorleef het tot die hede. Hierdie oorlewende spesies is Pteronia incana Burm Dc., Tripteris sinuata DC., Ehrharta calycina SM en Chaetobromus dregeanus Nees. Die hoogste vlak van werwing in 2001 is vir T sinuata aangeteken, gevolg deur P. incana, E. calycina en C. dregeanus. In September 2003, drie jaar na die aanvang van die eksperiment, was die hoogste getal oorlewende saailinge die van T sinuata, gevolg deur E. calycina, C. dregeanus en P. incana. Vyf verskillende bewerkings-metodes is gebruik om ontkiemingstempo en saailing oorlewing aan te help. Die aantal saailinge wat oorleef het varieer volgens die bewerkings-metode wat gevolge is en die grondtipe. Tripteris sinuata het die grootste aantal oorlewende saailinge gehad in al die bewerkings-metodes af van heuweltjies. Tripteris sinuata is daarom geselekteer om te analiseer vir die effek van verskillende bewerkings-metodes. Die tweede doelwit was om die inpak van Oxalis pes-caprae op spesie-diversiteit in die gerestoreerde ou land te bepaal deur die vermoë van hierdie spesie om in ou velde te versprei onder verskillende bewerkings-metodes te evalueer. Die multi-veranderlike ANOVA resultate het aangetoon dat daar 'n beduidende verskil in O. pes-caprae digtheid tussen heuweltjie en nie-heuweltjie (persele) en verskillende bewerkings-metodes was. Daar was 'n beduidende verskil in die digtheid van o. pes-caprae tussen verskillende bewerkingsmetodes. 'n Post Hoc LSD toets het 'n beduidende verkil in die digtheid van bogrondse O. pes-caprae plante tussen kontrole terreine (geen versteuring) vergeleke met persele wat een of ander vorm van grondversteuring ondergaan het aangedui. Daar was egter geen beduidende verskil in die volopheid van 0. pes-caprae op persele wat een of ander vorm van versteuring ondergaan het (i.e Skoongemaakte vs Getilde vs Geskottelde vs Geploegde persele) op heuweltjies nie. Daar was 'n beduidende verskil in die aantal O. pes-caprae bolle wat versamel is tussen blokke (op en af van heuweltjies) en beduidende verskille tussen die bewerkings-metodes. Daar was ook 'n beduidende verskil in bol-deursnitte tussen bewerkings-metodes wanneer dit tussen heuweltjie en nie-heuweltjie persele vergelyk is. Die bolle is in vier metingsklasse verdeel. Die grootste aantal klein (2-5 mm deursnit) en medium (5-8 mm deursnit) bolle is in die Getilde bewerkings-metode gevind. In kontras het die Kontrole behandeling (onbewerk) die grootste aantal groot (14-17 mm deursnit) en medium bolle gehad. Samevattend het T. sinuata die potensiaal om gebruik te word in die rehabilitasie van ou lande in kombinasie met die tilting bewerkings-metode. Aandag moet geskenk word aan die effek van 0. pes-caprae, veral op heuwetjies waar hierdie spesies 'n totale dominansie in die rehabilitasie eksperiment getoon het

Nomenclatural notes on southern African Oxalis species

Background: The correct author citation of Oxalis sonderiana (Kuntze) J.F.Macbr. and the validity and identity of the species Oxalis beneprotecta R.Knuth, Oxalis bullulata T.M.Salter and Oxalis pulchella Jacq. var. beneprotecta (R.Knuth) T.M.Salter are unclear. Objectives: To resolve the nomenclatural and taxonomic confusion surrounding these four taxa. Method: We studied relevant herbarium records (especially type material) of all the taxa, and paired this with scrutiny of all publications that bear reference to the nomenclature and taxonomy of these species. Results: The correct author citation for Oxalis sonderiana has been determined; Oxalis bullulata is confirmed as a distinct species, and the continued recognition of Oxalis beneprotecta as a variety of Oxalis pulchella is suggested. It is further ascertained that the name ‘Oxalis nidulans Turcz.’ is not a later homonym, but a reference to a misapplication of Oxalis nidulans Eckl. & Zeyh. to the type specimen of Oxalis sonderiana. Conclusion: These results clarify the current confusion surrounding these taxa in global herbaria and in national and international databases

Teratosphaeria stem canker of Eucalyptus : two pathogens, one devastating disease

CITATION: Aylward, J., et al. 2019. Teratosphaeria stem canker of Eucalyptus : two pathogens, one devastating disease. Molecular Plant Pathology, 20(1):8-19, doi:10.1111/mpp.12758.The original publication is available at https://bsppjournals.onlinelibrary.wiley.comBackground: Teratosphaeria gauchensis and T. zuluensis are closely related fungi that cause Teratosphaeria (previously Coniothyrium) stem canker disease on Eucalyptus species propagated in plantations for commercial purposes. This disease is present in many countries in which Eucalyptus trees are planted, and continues to spread with the international trade of infected plant germplasm. Taxonomy: Fungi, Ascomycota, Pezizomycotina, Dothideomycetes, Dothideomycetidae, Capnodiales, Teratosphaeriaceae, Teratosphaeria. Identification: The causal agents form dark masses of pycnidia that are visible on the surface of distinct stem cankers that typically form on young green stem tissues. Accurate diagnosis of the causal agents requires DNA sequence data. Host range: Nine species of Eucalyptus are known to be affected. Of these, E. grandis and its hybrids, which include some of the most important planting stock globally, appear to be particularly vulnerable. Disease symptoms: Small necrotic lesions develop on young green stem tissue. These lesions coalesce to form large cankers that exude gum. Epicormic shoots develop below the girdling canker and, in severe cases, trees die.https://bsppjournals.onlinelibrary.wiley.com/doi/full/10.1111/mpp.12758Publisher's versio

Inconsistent expression of the gigas effect in polyploid Oxalis

PREMISE : It is well-known that whole genome duplication (WGD) has played a significant role in the evolution of plants. The best-known phenotypic effect of WGD is the gigas effect, or the enlargement of polyploid plant traits. WGD is often linked with increased weediness, which could be a result of fitness advantages conferred by the gigas effect. As a result, the gigas effect could potentially explain polyploid persistence and abundance. We test whether a gigas effect is present in the polyploid-rich geophyte Oxalis, at both organ and cellular scales. METHODS : We measured traits in conspecific diploid and polyploid accessions of 24 species across the genus. In addition, we measured the same and additional traits in 20 populations of the weedy and highly ploidy-variable species Oxalis purpurea L., including measures of clonality and selfing as a proxy for weediness. Ploidy level was determined using flow cytometry. RESULTS : We found substantial variation and no consistent ploidy-related size difference, both between and within species, and across traits. Oxalis purpurea polyploids did, however, produce significantly more underground biomass and more bulbils than diploids, consistent with a potential role of WGD in the weediness of this species. CONCLUSIONS : Our results suggest a more nuanced role for the gigas effect, at least in Oxalis. It may be temporary, short-lived, and inconsistently expressed and retained on evolutionary time scales, but in the short term can contribute to lineage success via increased vegetative reproduction.DATA AVAILABILITY STATEMENT : Data are available from the Zenodo digital repository at: https://doi.org/10.5281/zenodo.7034366 (Becker et al., 2022).http://www.wileyonlinelibrary.com/journal/AJB2023-10-04hj2023Plant Production and Soil Scienc

Knoxdaviesia proteae is not the only Knoxdaviesia-symbiont of Protea repens

CITATION: Aylward, J., et al. 2015. Knoxdaviesia proteae is not the only Knoxdaviesia-symbiont of Protea repens. IMA Fungus, 6(2):471-476, doi:10.5598/imafungus.2015.06.02.10.The original publication is available at https://imafungus.biomedcentral.comTwo polyphyletic genera of ophiostomatoid fungi are symbionts of Proteaceae in southern Africa. One of these, Knoxdaviesia, includes two closely related species, K. proteae and K. capensis, that have overlapping geographical distributions, but are not known to share Protea host species. Knoxdaviesia capensis appears to be a generalist that occupies numerous hosts, but has never been found in P. repens, the only known host of K. proteae. In this study, extensive collections were made from P. repens and isolates were identified using DNA sequence comparisons. This led to the surprising discovery of K. capensis from P. repens for the first time. The fungus was encountered at a low frequency, suggesting that P. repens is not its preferred host, which may explain why it has not previously been found on this plant. The basis for the specialisation of K. proteae and K. capensis on different Protea species remains unknown.https://imafungus.biomedcentral.com/articles/10.5598/imafungus.2015.06.02.10Publisher's versio

Nitrogen-fixing bacteria and Oxalis – evidence for a vertically inherited bacterial symbiosis

CITATION: Jooste, M., et al. 2019. Nitrogen-fixing bacteria and Oxalis – evidence for a vertically inherited bacterial symbiosis. BMC Plant Biology, 19:441, doi:10.1186/s12870-019-2049-7.The original publication is available at https://bmcplantbiol.biomedcentral.comPublication of this article was funded by the Stellenbosch University Open Access Fund.Background: Plant-endophyte symbioses often revolve around nitrogen metabolism, and involve varying degrees of intimacy. Although evidence for vertical inheritance of nitrogen-fixing endophytic bacteria is increasing, it is confined mostly to crop plants, and to date no such system has been reported for geophytes. Methods: Bacterial endophytes associated with Oxalis, the most species-rich geophytic genus form the Cape Flora in southern Africa was studied. Culturable endophytes were isolated from surface-sterilized vegetative and reproductive plant organs for six host species at three locations. Colonies of microbes on various artificial media were morphotyped, enumerated and identified using sequence data. Filter exclusion experiments were conducted to determine if endophytes were vertically transmitted to seeds, determine if mucilage plays a role to actively attract microbes from the soil and to assess microbial richness isolated from the mucilage of Oxalis seedlings. Fluorescent microscopy was implemented in order to visualize endophytic bacteria in cryo-sectioned seeds. Results: Evidence for a novel, vertically transmitted symbiosis was reported. Communities of nitrogen-fixing and plant growth-promoting Bacillus endophytes were found to associate with selected Oxalis hosts from nitrogen-deficient environments of the Cape. Bacillus endophytes were ubiquitous and diverse across species and plant bodies, and were prominent in seeds. Three common nitrogen-fixing Bacillus have known oxalotrophic properties and appear to be housed inside specialised cavities (containing oxalates) within the plant body and seeds. Conclusions: The discovery of vertical transmission and potential benefits to both host and endophyte suggest a particularly tight mutualism in the Oxalis-endophyte system. This discovery suggests unexpected ways in which geophytes might avoid nitrogen deficiency, and suggest that such symbioses are more common than previously expected.https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-019-2049-7Publisher's versio