Otmar Spring

University of Hohenheim · Institute of Botany

Plasmopara halstedii (Farl.) Berl. et de Toni, is a biotrophic parasite of sunflower (Helianthus annuus). We genetically analysed 162 P. halstedii samples collected in the years 1982 to 2018, representing a 3,500 km west‐east transect across Europe, from France to the Krasnodar region in Southern Russia. To assess the population genetic structure a...

Orobanche cumana WALLR. is a host-specific root parasite of cultivated sunflowers with increasing economic importance in Europe, North Africa, and parts of Asia. While sesquiterpene lactones (STLs) released from sunflower roots were identified as natural germination stimulants of O. cumana seeds in the soil, the chemical nature of the signals guidi...

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not be...

Downy mildews caused by obligate biotrophic oomycetes result in severe crop losses worldwide. Among these pathogens, Pseudoperonospora cubensis and P. humuli, two closely related oomycetes, adversely affect cucurbits and hop, respectively. Discordant hypotheses concerning their taxonomic relationships have been proposed based on host-pathogen inter...

Peronospora tabacina is an obligate parasite that causes blue mold of tobacco. The pathogen reproduces primarily by sporangia, whereas the sexual oospores are rarely observed. A collection of 122 isolates of P. tabacina was genotyped using nine microsatellites to assess the population structure of individuals from subpopulations collected from cent...

Achillea atrata L. is a traditionally used medicinal plant. With its pronounced antimicrobial potential, this alpine Achillea species may also be used in modern phytotherapy to treat MRSA infections and prevent dermal infections, such as acne vulgaris. For the present study, A. atrata was cultivated in its natural habitat in Switzerland as well as...

In the present study, Achillea atrata L. and A. millefolium L. were compared for the first time with regard to their phenolic compound profile and antioxidant activity by applying the 2,2-diphenyl-picryl hydrazyl radical assay. For this purpose, aerial plant parts were consecutively extracted with solvents of increasing polarity (dichloromethane, n...

Sunflower, Helianthus annuus, is one of the world’s most important oil crops and sunflower oil is esteemed for its high content of unsaturated fatty acids and the occurrence of relatively high amounts of vitamin E and phytosterols. Reports on other secondary metabolites are rare, but recently identified bioactive sesquiterpene lactones in non-germi...

Various Achillea species are rich in bioactive compounds and are important medicinal plants in phytotherapy. In the present study, Achillea millefolium L., Achillea moschata Wulfen, and Achillea atrata L. were compared with respect to their phenolic profile and antibacterial activity against gram-positive bacteria strains (Staphylococcus, Propionib...

Despite intensive research in recent years, the biosynthetic route to costunolide in sunflower so far remained obscured. Additional P450 sequences from public sunflower transcriptomic database were screened to search for candidate enzymes which are able to introduce the 6α-hydroxy-group required for the esterification with the carboxy group of germ...

Smallanthus sonchifolius, also known as yacón, is an Andean crop species commercialized for its nutraceutical and medicinal properties. The tuberous roots of yacón accumulate a diverse array of probiotic and bioactive metabolites including fructooligosaccharides and caffeic acid esters. However, the metabolic diversity of yacon remains unexplored,...

Main conclusion: Tissue-specific occurrence and formation of endogenous sesquiterpene lactones has been assessed and suggests physiological function as antagonists of auxin-induced plant growth in sunflower. Sunflower, Helianthus annuus, accumulate high concentrations of bioactive sesquiterpene lactones (STL) in glandular trichomes, but in additio...

Oxathiapiprolin is a recently introduced fungicide with particular activity against hemibiotrophic and biotrophic oomycetes. For Plasmopara halstedii, the downy mildew of the sunflower, no detailed studies for the activity of the pure compound on the preinfectional and early infection stages in which the fungicide could most effectively interfere w...

Sesquiterpene lactones (STL) are a subclass of isoprenoids with many known bioactivities frequently found in the Asteraceae family. In recent years, remarkable progress has been made regarding the biochemistry of STL, and today the biosynthetic pathway of the core backbones of many STLs has been elucidated. Consequently, the focus has shifted to th...

Acting as chemical defense or signaling compounds, secondary metabolites (SMs) play an essential role in the evolutionary success of many angiosperm plant families. However, the adaptive advantages that SMs confer, and the influence of environmental and developmental factors on SMs expression, remains poorly understood. A study of taxa endemic to t...

Orobanche cumana is a root parasitic plant causing considerable yield losses in sunflower cultivation. The holoparasite fulfills its entire demand for water, minerals, and organic nutrients from the host’s vascular system. In this study, the ultrastructure of the phloem connection between the haustorium of young O. cumana tubercles and the sunflowe...

Peronospora tabacina Skalický [D.B. Adam], an obligate oomycete causing blue mold of tobacco, is an important pathogen causing significant economic losses. The pathogen rarely reproduces sexually, and the windblown asexual sporangia from infected plants are the source of yearly natural epidemics. A collection of 110 isolates of P. tabacina with s...

Supporting material for: Frey, M., Klaiber, I., Conrad, J. et al. Characterization of CYP71AX36 from Sunflower (Helianthus annuus L., Asteraceae). Sci Rep 9, 14295 (2019). https://doi.org/10.1038/s41598-019-50520-6

Since almost a century, sunflower cultivation is endangered by Plasmopara halstedii (Farlow) Berlese & de Toni, a biotrophic oomycete causing downy mildew symptoms. The pathogen has conquered four of the five continents, and through high genetic plasticity recurrently avoided being reliably controlled by the introduction of resistant host cultivars...

Plant biotrophic oomycetes cause significant production problems and economic losses in modern agriculture and are controlled by fungicide applications and resistance breeding. However, high genetic variability and fast adaptation of the pathogens counteract these measures. As a consequence of the “arms race,” new pathogen phenotypes recurrently oc...

Alternaria alternata is the most common fungal pathogen of tomatoes in Upper Egypt. Morphological identification of this fungus is challenging; therefore, this study searched for new classification tools based on molecular techniques. Using a dilution plating method, 67 strains of A. alternata were isolated from 34 samples of rotten tomato fruits r...

Fast recognition of host signals and early activation of infection mechanisms in Plasmopara viticola are decisive for successful infestation of Vitis vinifera. To better understand interactive processes at the first front line of combat between the pathogen and its host, a specific pre-infective stage was generated in a host-free system. Zoospore e...

Sesquiterpene lactones are a class of natural compounds well-known for their bioactivity and are characteristic for the Asteraceae family. Most sesquiterpene lactones are considered derivatives of germacrene A acid (GAA). GAA can be stereo-specifically hydroxylated by the cytochrome P450 enzymes (CYP) Lactuca sativa costunolide synthase CYP71BL2 (L...

Jatropha curcas, an entomophile Euphorphiaceae is an important bio-energy plant cultivated in some of the world's poorest countries. Commercial use of Jatropha honey could significantly improve the economic situation of plantations. This study evaluates the quality of 174 Jatropha honeys collected on Madagascar. Melissopalynology revealed a large p...

Downy mildew of sunflower is a recurrent threat for crop production and a permanent challenge for resistance breeding. Since 2016, a new pathotype of the oomycete Plasmopara halstedii has been found in fields of cutting sunflower in Southern Germany. Infection assays based on sunflower differential lines identified the pathogen as pathotype 354 whi...

Helianthus annuus (sunflower) displays non-glandular trichomes (NGT), capitate glandular trichomes (CGT), and linear glandular trichomes (LGT), which reveal different chemical compositions and locations in different plant tissues. With matrix-assisted laser desorption/ionization (MALDI) and laser desorption/ionization (LDI) mass spectrometry imagin...

Plasmopara halstedii virus (PhV) is one of the few characterized oomycete viruses. Although it is fully sequenced and well-studied in its genetic diversity, the exact classification and phylogenetic relationships of PhV remain uncertain. The only known virus with characteristics similar to PhV is the Sclerophthora macrospora Virus A (SmV-A). Both v...

Jatropha curcas L. as a bio energy plant belonging to the Euphorbiaceae family is gaining progressive importance over the last years. In 2012 and 2014 field experiments were carried out to assess the effects of cytokinins 6-Benzyladenine (BA) and Forchlorfenuron (CPPU) acting as plant growth regulators (PGRs). Number of flowers per inflorescence, f...

Millennial-old trees excavated from alluvial deposits or sampled from historical buildings are of high scientific value, e.g. for dating archeological wood as well as to reconstruct past climate variability. While chronologies are supported by isotopic measurements, climate reconstructions from year rings depend on reliable species identification a...

Viticulture in Europe and other parts of the world is continuously suffering significant economic loss from downy mildew epidemics. Although the infection biology of the pathogen Plasmopara viticola is well understood, little is known on the population diversity of this oomycete and on the mechanisms responsible for compatible or incompatible react...

Primula veris L. is an important medicinal plant with documented use for the treatment of gout, headache and migraine reaching back to the Middle Ages. Triterpenoid saponins from roots and flowers are used in up-to-date phytotherapeutic treatment of bronchitis and colds due to their expectorant and secretolytic effects. In addition to the wild type...

Genetically homogenous strains of Plasmopara halstedii differing in host specificity and fungicide tolerance were used to test the hypothesis that asexual genetic recombination occurs and may account for the high genotype diversity of this homothallic reproducing oomycete, which causes downy mildew in sunflower. Dual inoculation of sunflower seedli...

Amplification with primer pair INBL_WG_F1/R1 of the sequence parts specific for strain A (113 bp product) and strain B/C (165 bp product) analysed by capillary electrophoresis. Lanes 2–6, products obtained from single sporangia of the strains A-C and mixtures of 1A/1B and 1A/1C sporangia; lanes 9–12, products obtained from 10, 5, 2, 1 zoospores of...

Primer sequences used for DNA fingerprint with strain A-C. (PDF)

LR6 OM Sequence of BL-A4z (982 bp) and In-B5z (930 bp). Annealing sites for INBL_WG_F1/R1 in bold; 52 nt insert sequence of BL-A4z printed in lower case. (PDF)

PCR-products (inverted gel document) of strain A-C with primer LR6-Om (5‘-CGCCAGACGAGCTTACC). From lane A and B/C, the polymorphic bands at 930 bp (left arrow) and 980 bp (right arrow) were cloned and sequenced. Sequences of B and C were identical and differed from A in a 30 bp insertion. (TIF)

Isolation of single zoospores from agar using microcapillary techique. (TIF)

Sunflower is known to produce a variety of bisabolene-type sesquiterpenes and accumulates these substances in trichomes of leaves, stems and flowering parts. A bioinformatics approach was used to identify the enzyme responsible for the initial step in the biosynthesis of these compounds from its precursor farnesyl pyrophosphate. Based on sequence s...

The capitate glandular trichome is the most common type described to Asteraceae species. It is known for its ability to produce various plant metabolites of ecological and economical importance, among which sesquiterpenes lactones are predominant. In this paper, we applied microscopic, phytochemical and molecular genetics techniques to characterize...

Background Downy mildews are the most speciose group of oomycetes and affect crops of great economic importance. So far, there is only a single deeply-sequenced downy mildew genome available, from Hyaloperonospora arabidopsidis. Further genomic resources for downy mildews are required to study their evolution, including pathogenicity effector prote...

Uniseriate linear glandular trichomes occur on stems, leaves and flowering parts of Helianthus species and related taxa. Their metabolic activity and biological function are still poorly understood. A phytochemical study documented the accumulation of bisabolene type sesquiterpenes and flavonoids as the major constituents of the non-volatile metabo...

Downy mildews are oomycete pathogens that cause diseases on a wide range of plant species. Individual species have narrow host ranges and exhibit high degrees of host specialization. Their obligate biotrophic nature makes their study challenging compared to culturable oomycetes, such as Phytophthora spp. and Pythium spp. Next generation sequencing...

Peronospora tabacina is an obligate biotrophic oomycete that causes blue mold or downy mildew on tobacco (Nicotiana tabacum). It is an economically important disease occurring frequently in tobacco growing regions worldwide. We have sequenced and characterized the genomes of two P. tabacina isolates and mined them for pathogenicity related proteins...

Sunflower broomrape Orobanche cumana WALLR. is a rapidly growing threat to the oil crop production in many countries. Fast adaptation to new environments and increasing host resistance suggests that phenotypically distinctive populations of the weed may have evolved. The classification of the species and the differentiation of such populations on t...

Capitate glandular trichomes (CGT) of sunflower, Helianthus annuus, synthesize bioactive sesquiterpene lactones (STLs) within a short period of only a few days during trichome development. In the current project, the subcellular localization of H. annuus germacrene A monooxygenase (HaGAO), a key enzyme of the STL biosynthesis in sunflower CGT, was...

Sesquiterpene lactones in sunflowers, Helianthus spp., are important to interactions with pathogens, weeds and insects. Across a broad range of H. annuus, differences in composition of sesquiterpene lactones extracted from florets were found between wild and cultivated sunflowers, but also between distinct groups of inbreds used to produce sunflowe...

Downy mildews are obligate biotrophic oomycete pathogens that cause diseases on a wide range of plant species. We have utilized next generation sequencing technologies to efficiently generate de novo genome assemblies of geographically and temporally separated isolates of lettuce downy mildew (Bremia lactucae), spinach downy mildew (Peronospora eff...

Main conclusion Sunflower trichomes fully develop on embryonic plumula within 3 days after start of germination. Toxic sesquiterpene lactones are produced immediately thereafter thus protecting the apical bud of the seedling against herbivory. Helianthus annuus harbors non-glandular and two different types of multicellular glandular trichomes, na...

Plasmopara halstedii virus (PhV) is a ss(+)RNA virus that exclusively occurs in the sunflower downy mildew pathogen Plasmopara halstedii, a biotrophic oomycete of severe economic impact. The virus origin and its genomic variability are unknown. A PCR-based screening of 128 samples of P. halstedii from five continents and up to 40 y old was conducte...

The triploid perennial Helianthus x multiflorus L. is a beloved garden ornamental, but its phylogenetic origin has long been a source of discussion. Sequence comparison of genes involved in the biosynthesis of the sesquiterpene lactones was used to identify the common sunflower Helianthus annuus L. and the diploid taxon Helianthus decapetalus L. as...

White blister rust is an economically important emerging disease of sunflower caused by Pustula helianthicola. Knowledge on the host range of the pathogen particularly on different Helianthus species and its relative cultivars is of high relevance for disease management. Natural infection in the field on 13 sunflower genotypes with differentiating...

White blister rust (WBR) of sunflower caused by Pustula helianthicola is an important and often underestimated disease in many countries of the world. The epidemiology of the pathogen is not yet fully understood; particularly the role of oospores in primary infection and long distance dispersal. We analysed WBR severity in sunflower under natural c...

The lack of characterized isolates of Plasmopara viticola is a very limiting issue in the management of downy mildew of grapevine. Although molecular studies have previously confirmed a high diversity of this pathogen, there are still no phenotypically characterized pathotype strains or races available which could be used to study the mechanisms of...

Orobanche cumana is a serious threat for cultivation of sunflower in Europe and Asia. Germination of the parasite is induced by metabolites released from the host root system. The first germination stimulant from sunflower root exudate was recently identified as dehydrocostus lactone, a sesquiterpene lactone. Bioassay-guided fractionation of root e...

Blue mold of tobacco, caused by Peronospora tabacina, is a serious disease with severe commercial impact. Quarantine measures to reduce pathogen distribution affect commercial trade of tobacco even in processed stages, but survival of the pathogen after curing at high temperature or exposure to sunlight has not been investigated adequately. To asse...

Lychnophora ericoides (Vernonieae: Asteraceae), known as “Arnica-da-serra”, is restricted to Brazilian “Cerrado” and is used for wound healing. Its leaves produce a range of volatile sesquiterpenes original from the bisabolyl cations, also known as bisabolene-like derivatives. We have recently reported the bioactivity of essential oil fraction agai...

Previous studies have shown that capitate glandular trichomes (CGT) of the common sunflower, Helianthus annuus, produce sesquiterpene lactones (STL) and flavonoids, which are sequestered and accumulated between the apical cuticle and the wall of the tip cells. To explore the cellular structures required and putatively involved in the STL biosynthes...

Citation: Aschenbrenner A-K, Horakh S, Spring O. 2013. Linear glandular trichomes of Helianthus (Asteraceae): morphology, localization, metabolite activity and occurrence. AoB PLANTS 5: plt028; doi:10.1093/aobpla/plt028 Abstract. Capitate glandular trichomes of sunflower are well investigated, but detailed studies are lacking for the linear glandul...

Plasmopara halstedii virus (PhV) is an isometric virus recently found in the oomycete Plasmopara halstedii. The fully sequenced virus genome consists of two ss(+)RNA strands encoding for the virus polymerase and the coat protein, respectively. Most of previously screened field isolates of P. halstedii were found to harbor PhV, but effects of PhV on...

Peronospora tabacina is a major disease in tobacco cultures in many countries. Fungicide treatment with phenylamides is often used to control the pathogen, but resistance occurs and continuous application may cause selection pressure which influences the pathogen's population structure. Field isolates collected from blue mold incidences in Germany...

Sunflower white blister rust has become an important disease in many countries with intensive cultivation of the important oil crop. The biology of the pathogen is still partly unclear, particular with respect to its sexual reproduction and primary mode of infection. Zoospores released from sporangia of Pustula helianthicola were isolated individua...

Ten polymorphic microsatellite loci for the obligate biotrophic, oomycete pathogen of tobacco, Peronospora tabacina, were identified from a small insert genomic library enriched for GT motifs. Eighty-five percent of the 162 loci identified were composed of dinucleotide repeats, whereas only 4% and 11% were tri-and tetra-nucleotide repeats respectiv...

Sequencing of partial cox2 (part of the mitochondrial cytochrome-c-oxydase (COX) gene) was performed with samples from the oomycete genus Pustula, the white blister rusts of Asteraceae and related families. Sequence comparison uncovered several single nucleotide polymorphisms (SNPs) between P. spinulosa and host specific strains of Pustula isolated...

Sesquiterpene lactones (STLs) are terpenoid natural products possessing the γ-lactone, well known for their diverse biological and medicinal activities. The occurrence of STLs is sporadic in nature, but most STLs have been isolated from plants in the Asteraceae family. Despite the implication of the γ-lactone group in many reported bioactivities of...

Only very few viruses of Oomycetes have been studied in detail. Isometric virions were found in different isolates of the oomycete Plasmopara halstedii, the downy mildew pathogen of sunflower. However, complete nucleotide sequences and data on the genome organization were lacking. Viral RNA of different P. halstedii isolates was subjected to nucleo...

This review summarises the progress in research on sunflower downy mildew as reported in publications of the past 10 to 15years, the period since the last comprehensive review on Plasmopara halstedii. Particular attention is paid to subjects that showed much progress and may be of particular interest to sunflower pathologists, mycologists or molecu...

Over the last two decades few classes of secondary plant metabolites have attracted as much attention from phytochemists as sesquiterpene lactones (STL), which are characteristic metabolites of the Asteraceae. While Fischer et al.1 reviewed some 900 hundred different structures of naturally occuring STL in 1979, Seaman2 counted over 1300 only three...

Often high-quality MS/MS spectra of tryptic peptides do not match to any database entry because of only partially sequenced genomes and therefore, protein identification requires de novo peptide sequencing. To achieve protein identification of the economically important but still unsequenced plant pathogenic oomycete Plasmopara halstedii, we first...