Phelipanche Species Research Articles

Morphological diversity of pistil stigmas and its taxonomic significance of representatives of holoparasitic Orobanchaceae from Central Europe.

The stigma is the terminal part of the carpel which receives pollen during the pollination process. Although the role of the stigmas in pollination is the same for all angiosperms, stigmas structures are very diverse. This study aimed to evaluate intraspecific, interspecific and intergeneric stigmas variability and then find differences of the stigma morphology amongst 24 holoparasitic Orobanche and Phelipanche species and provide new insights into its potential taxonomic value. This paper was also focused on selecting the best diagnostic features that would be used for future stigma analysis in other species of Orobanchaceae. These analyses were conducted with fresh, dry and fixed material using stereomicroscopy from different locations from Central Europe. Twenty-one quantitative or qualitative morphological features were analysed. This study highlights the variation of stigma morphology and characters which are useful to improve the taxonomic understanding of problematic taxa. Thus, two main types of stigmas were established, based on tested features: 1-oval, rarely hemispherical in shape, most often one-coloured with lobes separated in Phelipanche stigmas; 2-spherical to hemispherical, rarely oval, multi-coloured with partially fused or separated lobes in Orobanche stigmas. The best diagnostic features of the stigmas for distinguishing the Orobanchaceae are the type and subtype of stigma, the length and area of the stigma, the width of single lobes, the width in the middle part of the stigma, the length of upper and lower separation in the middle part between lobes and the angle between lobes in the upper and lower part. The morphological features of the stigmas are important criteria for distinguishing genera, sections and subsections, as well as related species. In this study, we present the first stigma morphological studies for the most numerous genera from the tribe Orobancheae and this paper may determine features possible to use in solving certain taxonomic problems and evolutionary relationships of the species.

Molecular Characterization of a New Ecotype of Holoparasitic Plant Orobanche L. on Host Weed Xanthium spinosum L.

A species of Orobanche was observed on spiny cocklebur (Xanthium spinosum) for the first time in Iran and tentatively was named IR-Iso.This study was conducted to make a phylogenetic analysis of the Orobanche using 5.8S rRNA region sequences, and also to better understand its sequence pattern. The full-length ITS1-ITS2 region of the new Orobanche isolate was PCR-amplified from the holoparasitic plant parasitizing X. spinosum. Sequences of the amplicons from the isolate were 100% identical but differed by 5.6–6.7% from most homologous GenBank accessions to 37.9% divergence from distant species. The analysis of the molecular variance showed that variation between-population (61.9%, SE = 0.04) was larger than within-population. Neighbor-joining analysis placed the Iranian isolate in the same clade as most of the Orobanche and Phelipanche species. The isolate was more closely related to Orobanche aegyptiaca (from China), and this was confirmed by using a structure analysis. However, complementary analyses showed that the Iranian isolate has a unique nucleotide substitution pattern, and hence it was considered as an ecotype of O. aegyptiaca (ecotype Alborzica). In this paper we report on the association between this new ecotype of Orobanche and X. spinosum.

Assessment of weed root extracts for allelopathic activity against Orobanche and Phelipanche species

Broomrapes (Orobanche and Phelipanche species) are holoparasitic weeds that infect roots of crop hosts from Asteraceae, Brassicaceae, Apiaceae, Fabaceae, and Solanaceae. The parasitic weeds are difficult to control selectively without crop damage once attached to their roots. Identification of natural compounds with herbicidal activity against pre-attached broomrape stages can provide control alternatives. With the aim to identify plant species with efficacy for broomrape control, organic and residual aqueous phase extracts from roots of seventeen weed species common in south Spanish broomrape-infested fields were assessed as potential inducers of suicidal broomrape germination and as inhibitors of broomrape radicle growth. Assessments were carried out in vitro using seeds and seedlings of four noxious broomrape species, Orobanche crenata Forsk., Orobanche cumana Wallr., Orobanche minor Sm. and Phelipanche ramosa (L.) Pomel. While root extracts from all the weed species did not induce suicidal germination on O. crenata seeds, most of the extracts induced germination of P. ramosa except for those obtained from Amaranthus albus L., Amaranthus retroflexus L. and Convolvulus arvensis L. Moderate levels of germination activity were induced in O. cumana and O. minor seeds by some of the root extracts tested, with strongest induction obtained from Heliotropium europaeum L. on O. cumana seeds, and from Silybum marianum (L.) Gaertn. on O. minor seeds. For root extract inhibition of broomrape radicles, the extract from C. arvensis roots strongly inhibited radicles of all the broomrape species. While extracts from the other weed species induced low or negligible inhibition of O. cumana and O. crenata radicle growth, many inhibited P. ramosa and O. minor radicles. Exceptions were root extracts from Datura stramonium L., Heliotropium europaeum L., Malva sylvestris L., Solanum nigrum L. and Urtica dioica L., which did not inhibit P. ramosa radicles, and those from A. retroflexus, Datura stramonium L., Malva sylvestris L., Portulaca oleracea L. and S. nigrum, which did not inhibit O. minor radicles. Among the active organic extracts assessed, those showing promising chemical profiles were selected for future studies to characterize natural compounds with potential herbicidal activity on early stages of broomrape growth.

Effects of Benzoquinones on Radicles of Orobanche and Phelipanche Species.

The holoparasitic broomrape weeds (Orobanche and Phelipanche species) cause severe yield losses throughout North Africa, the Middle East, and Southern and Eastern Europe. These parasitic weeds form an haustorium at the tip of their radicles to infect the crop upon detection of the host-derived haustorium-inducing factors. Until now, the haustorial induction in the broomrapes remains less studied than in other parasitic plant species. Known haustorium-inducing factors active in hemiparasites, such as Striga and Triphysaria species, were reported to be inefficient for the induction of haustoria in broomrape radicles. In this work, the haustorium-inducing activity of p-benzoquinone and 2,6-dimethoxy-p-benzoquinone (BQ and DMBQ) on radicles of three different broomrapes, namely Orobanche cumana, Orobanche minor and Phelipanche ramosa, is reported. Additional allelopathic effects of benzoquinones on radicle growth and radicle necrosis were studied. The results of this work suggest that benzoquinones play a role in the induction of haustorium in broomrapes. Although dependent on the broomrape species assayed and the concentration of quinones used in the test, the activity of BQ appeared to be stronger than that of DMBQ. The redox property represented by p-benzoquinone, which operates in several physiological processes of plants, insects and animals, is invoked to explain this different activity. This work confirms the usefulness of benzoquinones as haustorium-inducing factors for holoparasitic plant research. The findings of this work could facilitate future studies in the infection process, such as host-plant recognition and haustorial formation.

A new race of sunflower broomrape (Orobanche cumana) with a wider host range due to changes in seed response to strigolactones

AbstractBroomrapes (Orobanche and Phelipanche species, Orobanchaceae) are obligate root parasites of dicotyledonous plants. This taxonomic group includes seven weedy parasites of agricultural crops that damage vegetables, sunflower (Helianthus annuus L.), and legumes. Processing-tomato (Solanum lycopersicum L.) fields in Israel have been recently found infested with a new broomrape, first identified as nodding broomrape (Orobanche cernua Loefl.) based on its host. However, its morphology resembled the closely related sunflower broomrape (Orobanche cumana Wallr.), an obligate parasite of sunflower. The new race (CUCE) parasitized sunflower, tomato, and tobacco (Nicotiana tabacum L.) in vitro, in a polyethylene bag system and in pots. Its seeds germinated in response to strigolactones (orobanchol, 5-deoxystrigol, 2′-epiorobanchol, and GR24) and dehydrocostus lactone (DCL), whereas O. cumana seeds responded only to DCL and GR24, and O. cernua only to strigolactones. Based on morphological similarities with O. cumana, shared molecular markers with O. cumana, ability to parasitize sunflower and respond to sunflower-germination stimulants, it was concluded that CUCE is a new race of O. cumana, with a host range expanding to Solanaceae crops. While being an important noxious weed of sunflower, this new O. cumana race is currently spreading and posing a threat to processing tomato in Israel. This finding is an alarming indication that broomrapes can shift host range and that similar new races of O. cumana could potentially appear in other countries.

Haustorium Inducing Factors for Parasitic Orobanchaceae.

Parasitic plants in the Orobanchaceae family include devastating weed species, such as Striga, Orobanche, and Phelipanche, which infest important crops and cause economic losses of over a billion US dollars worldwide, yet the molecular and cellular processes responsible for such parasitic relationships remain largely unknown. Parasitic species of the Orobanchaceae family form specialized invasion organs called haustoria on their roots to enable the invasion of host root tissues. The process of forming haustoria can be divided into two steps, prehaustorium formation and haustorium maturation, the processes occurring before and after host attachment, respectively. Prehaustorium formation is provoked by host-derived signal molecules, collectively called haustorium-inducing factors (HIFs). Cell wall-related quinones and phenolics have been known for a long time to induce haustoria in many Orobanchaceae species. Although such phenolics are widely produced in plants, structural specificities exist among these molecules that modulate their competency to induce haustoria in different parasitic plant species. In addition, the plant hormone cytokinins, structurally distinct from phenolic compounds, also trigger prehaustorium formation in Orobanchaceae. Recent findings demonstrate their involvement as rhizopsheric HIFs for Orobanche and Phelipanche species and thus address new activities for cytokinins in haustorium formation in Orobanchaceae, as well as in rhizospheric signaling. This review highlights haustorium-inducing signals in the Orobanchaceae family in the context of their host origin, action mechanisms, and species specificity.

Genuine and Sequestered Natural Products from the Genus Orobanche (Orobanchaceae, Lamiales).

The present review gives an overview about natural products from the holoparasitic genus Orobanche (Orobanchaceae). We cover both genuine natural products as well as compounds sequestered by Orobanche taxa from their host plants. However, the distinction between these two categories is not always easy. In cases where the respective authors had not indicated the opposite, all compounds detected in Orobanche taxa were regarded as genuine Orobanche natural products. From the about 200 species of Orobanche s.l. (i.e., including Phelipanche) known worldwide, only 26 species have so far been investigated phytochemically (22 Orobanche and four Phelipanche species), from 17 Orobanche and three Phelipanche species defined natural products (and not only natural product classes) have been reported. For two species of Orobanche and one of Phelipanche dedicated studies have been performed to analyze the phenomenon of natural product sequestration by parasitic plants from their host plants. In total, 70 presumably genuine natural products and 19 sequestered natural products have been described from Orobanche s.l.; these form the basis of 140 chemosystematic records (natural product reports per taxon). Bioactivities described for Orobanche s.l. extracts and natural products isolated from Orobanche species include in addition to antioxidative and anti-inflammatory effects, e.g., analgesic, antifungal and antibacterial activities, inhibition of amyloid β aggregation, memory enhancing effects as well as anti-hypertensive effects, inhibition of blood platelet aggregation, and diuretic effects. Moreover, muscle relaxant and anti-spasmodic effects as well as anti-photoaging effects have been described.

A large-scale analysis of soil and bioclimatic factors affecting the infestation level of tobacco (Nicotiana tabacum L.) by Phelipanche species

Soil and bioclimatic factors constitute key factors that influence the interaction between host plants and broomrape. The identification and quantification of the relationship between environmental variables and the level of infestation with Phelipanche aegyptiaca and Phelipanche ramosa was examined for 144 tobacco fields in surveys during two years 2003–2004 in Greece. The distribution of Phelipanche species was mapped using a Geographical Information System to reveal variability in the infestation level between the species, the cultivated types and the sampling areas. To assess the effect of abiotic factors on the level of infestation with Phelipanche species, soil and bioclimatic parameters were taken into account: soil texture, pH, organic matter content (OM), total humidity index (THI) and growing degree days (GDD). Univariate and multivariate statistics were used to examine the influence of the above parameters on Phelipanche intensity. ANOVA showed that the infestation varied significantly between the sampling areas and Phelipanche species, while significant differences were also detected among the regions in terms of the studied abiotic parameters. Correlation analysis demonstrated that the level of Phelipanche infestation correlated negatively with pH, THI and positively with OM. Multiple regression analysis suggested that soil and climatic variables together explained 63% of the infestation variance. Discriminant functions accounted for 90% of the total variation in the dataset. All statistical analyses demonstrated that pH, THI and OM were the most decisive variables for the severity of infestation. The two Phelipanche species were clearly discriminated, with P. ramosa being found at higher and P. aegyptiaca at a lower level of infestation. A parasitism specification was also observed between the two Phelipanche species and tobacco types. The findings provide constructive information for modelling broomrape infestation based on abiotic factors and create a baseline for future monitoring of broomrape distribution.

Seed Structure Characteristics of Orobanche cumana Populations

AbstractSunflower 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 the base of seed micromorphological characters were attempted. Morphometric measurements allowed the distinction of O. cumana from several other Orobanche and Phelipanche species. An irregularly thickened cell wall of the anticlinal testa cells differentiated O. cumana and O. cernua from O. caryophyllacea, O. crenata, O. minor, P. aegyptiaca, P. arenaria and P. ramosa. However, populations of sunflower broomrape from five European countries and China could not be separated from each other on the base of micromorphological seed characters. In contrast, length to width measurements indicated that the Asian samples had a slightly different seed shape which was less elongated than the European samples. However, this seemingly geographic effect may as well be a consequence of sampling which comprised a higher rate of the so-called modern races E-H in the European samples.

Ryecyanatines A and B and ryecarbonitrilines A and B, substituted cyanatophenol, cyanatobenzo[1,3]dioxole, and benzo[1,3]dioxolecarbonitriles from rye (Secale cereale L.) root exudates: Novel metabolites with allelopathic activity on Orobanche seed germination and radicle growth

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing heavy yield losses on important crops. Current control relies on the use of certain agronomic practices, resistant crop varieties, and herbicides, albeit success has been marginal. Agronomic practices such as the use of allelopathic species in intercropping or cover crops, or the use of direct seedling over residues of allelopathic species incorporate the principle of allelopathy exerted by molecules exuded from roots or released by crop residues to control broomrapes. In addition, the isolation of natural substances from root exudates of plants with potential to inhibit broomrape development opens the door to the design of new herbicides based on natural and benign sources. Ryecyanatines A and B and ryecarbonitrilines A and B, the first new substituted cyanatophenol, substituted cyanatobenzo[1,3]dioxole, and the latter two new substituted benzo[1,3]dioxolecarbonitriles were isolated from rye (Secale cereale L.) root exudates. They were characterized as 4-cyanato-2-methoxyphenol, 2-cyanato-benzo[1,3]dioxole, 2-methoxybenzo[1,3]dioxole-5-carbonitrile and benzo[1,3]dioxole-2-carbonitrile by spectroscopic (essentially NMR and HRESI MS spectra) methods. These compounds were investigated for allelopathic activity on Orobanche germination and development. Ryecarbonitriline A induced germination of Orobanche cumana seeds, and this germination can be considered as suicidal because O. cumana does not parasite rye roots and cannot survive without host resources beyond germination stage. In addition, ryecyanatine A promotes a rapid cessation of O. cumana, Orobanche crenata and Orobanche minor radicle growth with the promotion of a layer of papillae at the radicle tip in O. cumana and O. crenata hampering the contact of the parasite to the host. Ryecarbonitriline B also displayed the same activity although being less active than ryecyanatine A and mainly restricted to O. cumana.

Effect of fungal and plant metabolites on broomrapes (Orobanche and Phelipanche spp.) seed germination and radicle growth.

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which cause heavy yield losses on important crops. The development of herbicides based on natural metabolites from microbial and plant origin, targeting early stages on parasitic plant development, might contribute to the reduction of broomrape seed bank in agricultural soils. Therefore, the effect of metabolites belonging to different classes of natural compounds on broomrape seed germination and radicle development was assayed in vitro. Among the metabolites tested, epi-sphaeropsidone, cyclopaldic acid, and those belonging to the sesquiterpene class induced broomrape germination in a species-specific manner. epi-Epoformin, sphaeropsidin A, and cytochalasans inhibited germination of GR24-treated broomrape seeds. The growth of broomrape radicle was strongly inhibited by sphaeropsidin A and compounds belonging to cyclohexene epoxide and cytochalasan classes. Broomrape radicles treated with epi-sphaeropsidone developed a layer of papillae while radicles treated with cytochalasans or with sphaeropsidin A turned necrotic. These findings allow new lead natural herbicides for the management of parasitic weeds to be identified.

Potency of some synthetic stimulants and root exudates on the germination of Phelipanche spp.

Zararlı etkilerinin oldukça büyük olmasından dolayı, canavar otları, özellikle Solanaceae ve Fabaceae familyalarına ait bazı kültür bitkilerinin en önemli sorunu olarak değerlendirilmektedir. Phelipanche ramosa L. ve Phelipanche aegyptiaca (L.) Pers. Türkiye’de ve diğer Akdeniz ülkelerinde daha çok domates üretim alanlarında sorun olmaktadır. Bu çalışma bazı bitki kök salgılarının ve sentetik stimulant maddelerin, bu canavar otu türlerinin çimlenme oranına etkisini belirlemek amacıyla kontrollü koşulların sağlandığı laboratuvarlarda yürütülmüştür. Çalışmada sentetik çimlenme stimulantları olarak GR24 (0.1-1 ppm), GR7 (0.1-1 ppm) ve GA3 (10 ppm), kök salgısı olarak keten, pamuk, soya, fasulye, bezelye, börülce, domates, mercimek, hıyar ve tütün fideleri kullanılmıştır. Çalışmadaki sentetik stimulant maddeler, kök salgıları ile ilk kez bu çalışmada karşılaştırılmıştır. Denemelerden elde edilen ortalama sonuçlara göre; sentetik stimulantlar ve kök salgıları 1 yaşındaki P. ramosa çimlenme oranını sırasıyla % 50-77 ve 0 - 16 arasında artırırken, 3 yaşındaki P. aegyptiaca için elde edilen ortalama değerler % 62-95 ve 0-63 arasında olmuştur. Sonuç olarak, sentetik stimulant maddelerin canavar otlarının çimlenme oranını önemli derecede artırdığı belirlenmiştir. Due to their huge harm effects, broomrapes ( Orobanche / Phelipanche spp) are considered the biggest problem of some cultivated plants especially belong to Solanaceae and Fabaceae families. Phelipanche ramosa L. and Phelipanche aegyptiaca (L.) Pers. cause big problem especially in tomato grown areas in Turkey and the other Mediterranean countries. This study was conducted to determine the effect of some synthetic stimulant substances and root exudates on the germination rate of the broomrape species in controlled laboratory conditions. In this study GR24 (0.1-1 ppm), GR7 (0.1-1 ppm) and GA3 (10 ppm) were used as synthetic germination stimulants; flax, cotton, soybean, bean, pea, cowpea, tomato, lentil, cucumber and tobacco seedlings were used as exudates. The synthetic stimulants were compared with the root exudates for the first time in this study. As a result of the studies it was determined that synthetic stimulants significantly increase the germination rate of Phelipanche species. According to average results of the trials; synthetic stimulants and root secretions increased the germination rate of P. ramosa at one years of age between 50 - 77 and 0 - 16 respectively, otherwise average datas for P. aegyptiaca at three years of age are between 62 - 95 and 0 - 63. As a result of the studies it was determined that synthetic stimulants were significantly increased the germination rate of Phelipanche species.

A thermal time model for predicting parasitism of Orobanche cumana in irrigated sunflower—Field validation

A major part of its life cycle, the root parasitic weed broomrapes (Orobanche and Phelipanche species) grow underground. Predicting their developmental stages underground is a challenge that can be met by using a modeling approach, as reported for Phelipanche aegyptiaca and Orobanche cumana, in sunflower grown under temperature-controlled conditions. In those studies the relation between parasitism dynamics and thermal time was described by Sigmoid functions. To confirm these relations and calibrate the parameters under field conditions, a 5-year field study was conducted in nine fields in Israel, in various locations under different climatic conditions. As a result, a robust thermal time model that allows precisely estimating the parasitism dynamics was developed. Development of O. cumana in the subsurface was detected, monitored and recorded non-destructively in situ by the use of a minirhizotron. The data from field experiments, conducted in 2006, 2007, 2008 and 2009, were used for model calibration. For model validation, five field experiments were independently performed in 2009 and 2010. To relate the number of attachments and shoot emergence to thermal time, the following equations were tested: Sigmoid, Gompertz (both three-parameter) and Weibull (four parameters with lag phase). In the calibration studies, the number of attachments was best fitted to thermal time using the Weibull equation, which further resulted in very good fit in the validation studies for number of attachments (RMSE=0.066; R2=0.99) and O. cumana shoot emergence (RMSE=0.0096; R2=0.97). The Weibull equation thus adds a biological dimension (lag phase) to the model that the other equations lack, as the lag phase allows estimating the precise timing of parasite attachment to host roots and shoot emergence. This information is crucial in any attempt to develop control strategies for these parasitic weeds.

RNA trafficking in parasitic plant systems

RNA trafficking in plants contributes to local and long-distance coordination of plant development and response to the environment. However, investigations of mobile RNA identity and function are hindered by the inherent difficulty of tracing a given molecule of RNA from its cell of origin to its destination. Several methods have been used to address this problem, but all are limited to some extent by constraints associated with accurately sampling phloem sap or detecting trafficked RNA. Certain parasitic plant species form symplastic connections to their hosts and thereby provide an additional system for studying RNA trafficking. The haustorial connections of Cuscuta and Phelipanche species are similar to graft junctions in that they are able to transmit mRNAs, viral RNAs, siRNAs, and proteins from the host plants to the parasite. In contrast to other graft systems, these parasites form connections with host species that span a wide phylogenetic range, such that a high degree of nucleotide sequence divergence may exist between host and parasites and allow confident identification of most host RNAs in the parasite system. The ability to identify host RNAs in parasites, and vice versa, will facilitate genomics approaches to understanding RNA trafficking. This review discusses the nature of host–parasite connections and the potential significance of host RNAs for the parasite. Additional research on host–parasite interactions is needed to interpret results of RNA trafficking studies, but parasitic plants may provide a fascinating new perspective on RNA trafficking.

Soyasapogenol B and trans‐22‐dehydrocam‐ pesterol from common vetch (Vicia sativa L.) root exudates stimulate broomrape seed germination

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing severe yield losses on important crops. Control strategies have largely focused on agronomic practices, resistant crop varieties and herbicides, albeit with marginal success. An alternative control method is the induction of suicidal seed germination with natural substances isolated from root exudates of host and non-host plants. Soyasapogenol B [olean-12-ene-3,22,24-triol(3β,4β,22β)] and trans-22-dehydrocampesterol [(ergosta-5,22-dien-3-ol, (3β,22E,24S)] were isolated from Vicia sativa root exudates. They were identified by comparing their spectroscopic and optical properties with those reported in the literature. Soyasapogenol B was very specific, stimulating the germination of O. minor seeds only, whereas trans-22-dehydrocampesterol stimulated P. aegyptiaca, O. crenata, O. foetida and O. minor. Soyasapogenol B and trans-22-deydrocampesterol were isolated for the first time from Vicia sativa root exudates, and their biological activity as stimulants of Orobanche or Phelipanche sp. seed germination was reported.

Colonisation of field pea roots by arbuscular mycorrhizal fungi reduces Orobanche and Phelipanche species seed germination

Fernández‐Aparicio M, García‐Garrido JM, Ocampo JA & Rubiales D (2010). Colonisation of field pea roots by arbuscular mycorrhizal fungi reduces Orobanche and Phelipanche species seed germination. Weed Research50, 262–268.SummaryPea (Pisum sativum) is an important grain legume crop whose cultivation in the Mediterranean basin and West Asia is severely constrained by infection by the weedy root parasite Orobanche crenata (crenate broomrape). Pea is a false host of other species such as O. minor, O. foetida and Phelipanche aegyptiaca. In the present experiments, we demonstrate that seed germination of the Orobanche and Phelipanche species examined is reduced in the presence of root exudates from pea plants colonised by arbuscular mycorrhizal (AM) fungi, Glomus mosseae and G. intraradices. Reduced germination was due to the effect of the AM fungi and not to the microbial populations potentially present in the soil inoculum. This protective effect of mycorrhizae was noticeable after 35 days of AM colonisation for O. crenata, O. foetida and P. aegyptiaca, but at least 45 days of colonisation were needed to get some reduction of O. minor germination.

Polyphenols, including the new Peapolyphenols A-C, from pea root exudates stimulate Orobanche foetida seed germination.

Three new polyphenols, named peapolyphenols A-C, together with an already well-known polyphenol and a chalcone (1-(2,4-dihydroxyphenyl)-3-hydroxy-3-(4-hydroxyphenyl)-1-propanone and 1-(2,4-dihydroxyphenyl)-3-(4-methoxyphenyl)propenone) were isolated from pea root exudates. They were found to strongly stimulate Orobanche and Phelipanche species seed germination. Interestingly, only peapolyphenol A, 1,3,3-substituted propanone, and 1,3-disubstituted propenone had specific stimulatory activity on O. foetida, excluding any other Orobanche or Phelipanche species tested. This species specificity is relevant, as O. foetida does not respond to the synthetic strigolactone analogue GR24, commonly used as a standard for germination assays. As characterized by spectroscopic methods, peapolyphenols A-C proved to be differently functionalized polyphenols with hydroxy and methoxy groups on both the aromatic rings and the propyl chain.

Revisiting strategies for reducing the seedbank of Orobanche and Phelipanche spp.

SummaryWeedy Orobanche and Phelipanche species are important in Southern and Eastern Europe, the Middle East and North Africa, and have recently been reported in the USA, Australia and some countries in South America. Rather than being controlled, the Orobanche and Phelipanche problem is increasing, both in intensity and in acreage. Large areas of new territory are at risk of invasion, if care is not immediately taken to limit the introduction of parasitic seeds and to educate farmers and others to be alert for new infestations. There is an urgent need to re‐evaluate novel integrated Orobanche and Phelipanche management programmes that will allow a better control of the parasite species and limit their distribution. The main obstacle in the long‐term management of Orobanche and Phelipanche infested fields is the durable seedbank, which may remain viable for decades in the field. Large quantities of long‐lived seeds give the parasite genetic adaptability to changes in host resistance and cultural practices. As long as the seedbank is not controlled, the need to control the parasite will persist whenever a susceptible host is grown in the infested field. We discuss strategies for seedbank reduction, paying particular attention to cultural practices, whereas chemical and biological control methods are covered by other reviews in this issue.

Comparative proteomic analysis of Orobanche and Phelipanche species inferred from seed proteins

Summary Orobanche and Phelipanche species are root parasitic plants some of which infect important crops, causing extensive damage. In an attempt to unravel molecular systematic in these genera using protein markers, we established the protein profile of twelve species by two‐dimensional gel electrophoresis (2‐DE). Proteins were detected by Sypro Ruby staining and the gel images were digitalised and analysed. The 2‐DE maps contained from 30 to 140 protein spots for the analysed species. A virtual master gel was built with spots present in all species and revealing the presence of 260 protein spots. Only one protein was monomorphic, while 143 were unique to a single species. Proteins were scored for the presence or absence of homologous spots to create a binary matrix. Phylogenetic analysis was carried out using maximum parsimony and distance method. The trees obtained were rooted using Cistanche phelypaea as an out‐group. Both analyses showed Orobanche as a monophyletic group. AMOVA analysis revealed phenotypic diversity between species within genera, as well as a considerable level of variation between genera. This is a first step to help in the phylogenetic classification of parasitic plants by means of proteomics.

Recognition of root exudates by seeds of broomrape (Orobanche and Phelipanche) species

The long co-existence of broomrapes and their hosts within the same environment has culminated in a strong adaptation and effective parasitism. As a first step of specialization in the parasitic process, seed receptors of parasitic plant species vary in their ability to recognize compounds released by their hosts. This work aims to investigate potential patterns for the reception requirements needed to activate germination within Orobanche and Phelipanche species. Induction of the germination of seeds of nine Orobanche and Pheliphanche species by root exudates of 41 plant species was studied and subjected to biplot multivariate analysis. A high level of specialization in root exudate recognition was found in Orobanche densiflora, O. gracilis and O. hederae, which germinated almost exclusively in contact with root exudates from the plants they infect in nature. At the opposite extreme, Phelipanche aegyptiaca, P. ramosa and O. minor were highly generalist, germinating when in contact with the root exudates of most plant species. Orobanche crenata, O. cumana and O. foetida showed intermediate behaviour. A universal germination stimulant for all broomrape species has not being identified to date. The synthetic stimulant GR24 is active against most of the weedy broomrape species, but fails with the non-weedy species tested in this study and with the very recent weedy species O. foetida. In addition, germination behaviour of broomrape species depends on the crop plant tested. Weedy broomrapes with a broad host spectrum respond better to the different exudates released by a wide range of crops and wild species than do non-weedy broomrapes, which have a narrow host spectrum and are more restricted to their host range. Root exudates of many plant species were active in stimulating germination of seeds of Orobanche and Phelipanche species for which they are not described as hosts, representing interesting examples of potential trap crops.