Broomrape Species Research Articles

Gene silencing in broomrapes and other parasitic plants of the Orobanchaceae family: mechanisms, considerations, and future directions.

Holoparasites of the Orobanchaceae family are devastating pests causing severe damage to many crop species and are nearly impossible to control with conventional methods. During past decades RNA interference (RNAi) has been seen as a promising approach to control various crop pests. The exchange of small RNAs (sRNAs) between crops and parasitic plants has been documented indicating a potential for the development of methods to protect them via the delivery of the sRNAs to parasites, called host-induced gene silencing (HIGS). Here we describe various approaches used for gene silencing in plants and suggest solutions to improve the long-distance movement of the silencing triggers to elevate the HIGS efficiency in parasitic plants. We also investigate the important biological processes during parasites life cycle with a focus on broomrape species, providing several appropriate target genes that can be used in, especially, multiplex gene silencing experiments. We also touch on how the application of nanoparticles can improve the stability and delivery of the silencing triggers, highlighting its potential for parasitic plants control. Finally, suggestions for further research and possible directions for RNAi in parasitic plants are provided.

Study of preliminary qualitative screening and evaluation of alkaloids and flavonoids compounds of some Orobanche species growing in Iraq

Among 27 Orobanche species growing in Iraq, only O. aegyptiaca and O. ramosa (recently Phelipanche aegyptiaca and P. ramosa) have been studied phytochemically. Preliminary phytochemical screening revealed the presence of alkaloids, phenols, flavonoids, terpenes, resins, steroids, saponins (present or absent) and tannins in the areal parts of all tested species. HPLC results indicated the presence of six alkaloid compounds (oxo sparteine, isosparteine, retamine,13-hydroxylupanine, lupanine and sparteine) and three phenolic compounds (isoverbascoside,caffeic acid and verbascoside) in all Orobanche s.l.taxa investigated . These parasitic taxa showed high amounts of the alkaloid Lupanine and the phenylpropanoid verbascoside. In this study, O.ramosa is the richest broomrape species in secondary metabolites.

Understanding life cycle of parasitic weed Phelipanche ramosa infesting Brassica juncea in India: new host species and seed coat structure

ABSTRACT Broomrape (Phelipanche ramosa) is an obligate root parasitic plant that is known to infest many important crops. It is emerging as a serious biotic threat for Brassica juncea cultivation in India. There is very limited information available about broomrape species and its infestation in B. juncea. Hence, the present study encompassed a comprehensive five-year field survey spanning from 2018 to 2023 of 47 different B. juncea fields in the states of Rajasthan and Haryana in India. The level of broomrape infestation varied from season to season and field to field. In the B. juncea fields, broomrape with blue/violet color corolla, along with occasionally white color type were also noticed. The hairy anther, corolla shape and use of mitochondrial DNA-specific molecular markers revealed that both these broomrape types belong to Phelipanche ramosa. Scanning electron microscopy (SEM) analysis showed that P. ramosa seeds have varying shapes and seed coat have fibrillar periclinal cell wall. In addition to all the known host species for P. ramosa till date, we also identified a new host, a wild Brassicaceae weed species; Lepidium didymum in Haryana. The presence of an alternative weed host may help P. ramosa survive even in the absence of major crop host species. Overall, the present study revealed some insights into the P. ramosa-B. juncea host-parasite complex and its effect on B. juncea which could be further investigated in more detail.

Sesquiterpene Lactones Isolated from Centaurea cineraria L. subsp. cineraria Inhibit the Radicle Growth of Broomrape Weeds.

The plant Centaurea cineraria L. subsp. cineraria has been investigated as a potential source of inhibitors of broomrape radicle growth. The latter are weeds that pose a threat to agriculture and for which there are few methods available for the control of infestations. Four sesquiterpene lactones have been isolated from C. cineraria L. subsp. cineraria aerial parts and identified as isocnicin, cnicin, salonitenolide, and 11β,13-dihydrosalonitenolide using spectroscopic, spectrometric, and optical methods. Salonitenolide and 11β,13-dihydrosalonitenolide have been isolated for the first time from this plant. Tested at 1.0-0.1 mM against the broomrape species Phelipanche ramosa, Orobanche minor, Orobanche crenata, and Orobanche cumana, isocnicin, cnicin, and salonitenolide demonstrated remarkable inhibitory activity (over 80% in most of the cases) at the highest concentrations. Structure-activity relationship conclusions indicated the significance of the α,β-unsaturated lactone ring. In addition, the synthetic acetylated derivative of salonitenolide showed the strongest activity among all compounds tested, with inhibitions close to 100% at different concentrations, which has been related to a different lipophilicity and the absence of H-bond donor atoms in its structure. Neither the extracts nor the compounds exhibited the stimulating activity of broomrape germination (induction of suicidal germination). These findings highlight the potential of C. cineraria to produce bioactive compounds for managing parasitic weeds and prompt further studies on its sesquiterpene lactones as tools in developing natural product-based herbicides.

Managing Root Parasitic Weeds to Facilitate Legume Reintroduction into Mediterranean Rain-Fed Farming Systems

Grain and forage legumes are important sources of food and feed, key for sustainable agriculture given the environmental services they provide. However, their cultivation is hampered in the Mediterranean Basin and Near East by the widespread occurrence of the root parasitic weed crenate broomrape (Orobanche crenata). Other broomrape species such as O. minor, O. foetida, and Phelipanche aegyptica are also of local importance. As for other parasitic weeds, a number of management strategies have been proposed, but considering that temperate legumes in the area are low-input crops, these strategies are largely uneconomical or hard to achieve, leaving the use of resistant cultivars as the most desirable option. Breeding for broomrape resistance is not an easy task, but significant progress has been achieved by classical breeding and selection and will profit from recent developments in phenomics and genomics. Here, achievements and prospects in broomrape management and resistance breeding are presented and critically discussed.

Inhibition of broomrape germination by 2,4-diacetylphloroglucinol produced by environmental Pseudomonas.

Parasitic weeds such as broomrapes (Phelipanche ramosa and Orobanche cumana) cause severe damage to crops and their development must be controlled. Given that phloroglucinol compounds (PGCs) produced by environmental Pseudomonas could be toxic towards certain plants, we assessed the potential herbicidal effect of the bacterial model Pseudomonas ogarae F113, a PGCs-producing bacterium, on parasitic weed. By combining the use of a mutagenesis approach and of pure PGCs, we evaluated the in vitro effect of PGC-produced by P. ogarae F113 on broomrape germination and assessed the protective activity of a PGC-producing bacteria on oilseed rape (Brassica napus) against P. ramosa in non-sterile soils. We showed that the inhibition of the germination depends on the PGCs molecular structure and their concentrations as well as the broomrape species and pathovars. This inhibition caused by the PGCs is irreversible, causing a brown coloration of the broomrape seeds. The inoculation of PGCs-producing bacteria limited the broomrape infection of P. ramosa, without affecting the host growth. Moreover, elemental profiling analysis of oilseed rape revealed that neither F113 nor applied PGCs affected the nutrition capacity of the oilseed rape host. Our study expands the knowledge on plant-beneficial Pseudomonas as weed biocontrol agents and opens new avenues for the development of natural bioherbicides to enhance crop yield.

First Report of the Branched Broomrape (Phelipanche schultzii (Mutel) Pomel.) on Fennel (Foeniculum vulgare Mill.) in Morocco

Holoparasitic broomrape weeds (Orobanche and Phelipanche spp.) are a major biotic constraint limiting the production of important food crops. Parasitism caused by Phelipanche spp. is considered to be a serious threat, particularly in the Mediterranean region. In this study, the broomrape species collected from infested fennel fields in Sid L’Mokhtar in the Central West of Morocco was described and identified morphologically and molecularly. For molecular identification, 700 bp ITS regions were PCR-amplified from two representative individuals, OA and OY-4. The obtained sequences exhibited more than 99% similarity with the P. schultzii sequence (MT026593). In addition, maximum likelihood analysis placed our species with other referred P. schultzii in the same clade. Through molecular analysis, the broomrape species attacking fennel was identified as P. schultzii. This is the first record of the broomrape species P. schultzii parasitizing fennel (Foeniculum vulgare syn. Foeniculum officinale) in Morocco. Therefore, it should be considered that this parasite could spread to other cultivated fields causing severe yield losses, requiring urgent action through efficient control measures to avoid further spread of this parasitic weed.

К морфофизиологической коэволюции заразихи (Orobanche cumana) и подсолнечника

The accelerated morphofunctional variability of Orobanche cumana, a flowering parasitic plant of the family Orobanchaceae, can be traced to the influence of anthropogenic factors. This broomrape species is an obligate parasite of sunflower. Continuous breeding of the crop for immunity to broomrape has been conducted in the Russian Federation for more than 100 years. In the last 30 years, the accelerated return of sunflower in crop rotation to the previous field in 1-3 years (instead of the scientifically justified 8–10 years) resulted in the rapid emergence of new races of broomrape and contamination of fields with its seeds, which provided intense competition between individuals for the nutrition received from the host plant. Under these conditions, interrow cultivation in sunflower sowings infested by the broomrape contributed to permanent injury of developing stems of many individuals of the parasite, which led to the removal of apical dominance of one shoot in some species of the broomrape. There have appeared the bushy forms with equal development of many shoots from a tubercle, which were detected for the first time by us. Strengthening of the haustorial part of the parasitic plant, externally manifested as thickening of the host plant root under the tubercle, was required for feeding the multiple shoots. Such thickening is not a defensive reaction of the host plant but is caused by changes in the haustorial area of the parasite and is observed when sunflower roots are affected by species of the race G of O. cumana that became widely spread and dominant during the last decade. Thus, in the co-evolution of the parasitic plant and its host, we first discovered bushy forms of O. cumana and their characteristic change in the haustorial zone, which is externally manifested by the visible thickening of the sunflower root in this area.

Characterization of Conyza bonariensis Allelochemicals against Broomrape Weeds.

The study of allelopathic activity of plants and the isolation and characterization of the responsible allelochemicals can lead to the development of environment friendly alternative approaches to weed control. Conyza species are invasive weeds that use allelopathic activity as part of a successful strategy to outcompete neighboring plants. Broomrape weeds are parasitic plants that use host-induced germination and the formation of a haustorium as strategies to infect host plants. The control of broomrape infection in most affected crops is limited or non-existing. In the current study, we investigated the allelopathic activity of Conyza bonariensis organic extracts in suicidal germination and radicle growth of four broomrape species (Orobanche crenata, Orobanche cumana, Orobanche minor and Phelipanche ramosa). A bioactivity-driven fractionation of Conyza bonariensis extracts led to the identification of two germination-inducing molecules and two growth-inhibitory compounds. The germination-inducing metabolites had species-specific activity being hispidulin active on seeds of O. cumana and methyl 4-hydroxybenzoate active in P. ramosa. The growth-inhibitory metabolites (4Z)-lachnophyllum lactone and (4Z,8Z)-matricaria lactone strongly inhibited the radicle growth of all parasitic weed species studied. Some structure-activity relationships were found as result of the study herein presented.

Seed germination responses of broomrape species (Phelipanche ramosa and Phelipanche aegyptiaca) to various sanitation chemicals

AbstractBranched broomrape, an obligate root parasitic weed, has recently re-emerged in tomato fields in several California counties. California produces more tomato than any other state, and the outbreak of this noxious weed could potentially wreak havoc on the industry’s economy. Preventive measures must be taken to stop or reduce the spread of branched broomrape seeds to other areas. Branched broomrape can produce thousands of tiny seeds, which can easily spread with farm machinery over short and long distances. To prevent branched broomrape seed dispersal, sanitation and disinfection of farm equipment are necessary before entering a new farm. We tested the effectiveness of various ammonium compounds, including didecyl dimethyl ammonium chloride (DDAC), alkyl dimethyl benzyl ammonium chloride (ADBC), didecyl dimethyl ammonium bromide (DDAB), ammonium bromide (AB), and ammonium chloride (AC) on prevention of branched broomrape seed germination. Dose-response analysis showed that three chemical products, ADBC, DDAB, and DDAC, could completely inhibit branched broomrape seeds (potentially making them nonviable) at 1%, 1%, and 10% wt/vol concentrations, respectively. These three compounds were further tested in an exposure duration experiment that additionally included Egyptian broomrape. Only 10 min of exposure to these compounds was needed to prevent germination of both branched and Egyptian broomrape seeds at 1% (ADBC, DDAB) and 10% wt/vol (DDAC). Lower concentrations can provide similar inhibition effects when combined with longer exposure times. Egyptian broomrape seeds were more sensitive than branched broomrape seeds. Findings suggest that quaternary ammonium compounds could be used as potential sanitation agents to disinfect agriculture machinery from branched and Egyptian broomrape seeds.

Hyperspectral imaging facilitates early detection of Orobanche cumana below-ground parasitism on sunflower under field conditions

• Early detection of O. cumana in soil subsurface facilitates site-specific control. • Hyperspectral imaging of host leaves, in field conditions, detects O. cumana at an early parasitism stage. • Leaf segmentation improves classification accuracy. • Multispectral data is sufficient for classification of parasitized plants. Sunflower broomrape ( Orobanche cumana ) is a root parasitic weed that severely limits sunflower yield in large areas of Europe and Asia. Early detection of the parasite can facilitate site-specific control of this weed. However, most of its life-cycle takes place in the soil sub-surface and by the time that O . cumana shoots emerge, the damage to the crop is irreversible. The main aim of this study was to evaluate the potential use of hyperspectral imaging for the early detection of parasitism by monitoring changes in spectra obtained from the host plants. A field experiment was conducted on infested and non-infested sunflower plants, imaged by a ground-based hyperspectral camera at two early parasitism stages that are relevant for herbicide application. A logistic regression model was used to classify infected and non-infected plants, 31 and 38 days after sunflower planting, with 76 and 89% accuracy, respectively. A partial dataset, containing only 10 spectral bands of the hyperspectral dataset, gave 69 and 82% accuracy, indicating the potential of multi-spectral sensors for the detection task. Sampling pixels from specific sunflower leaf segments improved the classification compared to non-specific sampling. This study thus contributes to establishing a basis for future development of site-specific weed management of O. cumana and of other broomrape species.

Complex Mixture of Arvensic Acids Isolated from Convolvulus arvensis Roots Identified as Inhibitors of Radicle Growth of Broomrape Weeds

Broomrape weeds (Orobanche and Phelipanche spp.) are noxious parasites that infect crops using haustoria formed at the tip of their radicles. Dichloromethane extract obtained from the roots of Convolvulus arvensis strongly inhibits the radicle growth of broomrape weeds. A complex mixture of arvensic acids was isolated as the metabolites responsible of the inhibitory activity of C. arvensis extract against broomrape radicle growth via activity-guided fractionation and 1H NMR and ESI MS data. We showed that the exposure of broomrape seedlings to this arvensic acids mixture results in a strong phytotoxic effect on their radicles in four broomrape species infecting a wide range of crops worldwide. This discovery paves the way for the synthesis of new bioherbicides and could contribute to the development of efficient and sustainable management strategies for broomrape weeds, for which control in many crops is limited or non-existing.

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.

Wild Lathyrus species as a great source of resistance for introgression into cultivated grass pea (Lathyrus sativus L.) against broomrape weeds (Orobanche crenata Forsk. and Orobanche foetida Poir.)

AbstractBroomrape weeds (Orobanche spp.) are root holoparasitic plants that cause serious damage to a range of legume crops in the Mediterranean and sub‐Saharan African regions. Grain yield of cultivated species of grass pea (Lathyrus sativus L.) is almost negligible at the highest infection severity of Orobanche. Crop wild relatives (CWRs) have emerged as a novel source for many traits in diverse crops. Lathyrus is one of the largest genera with more than 160 species. In the present study, we screened 285 accessions representing 13 Lathyrus species for their reactions against two common broomrape species, Orobanche crenata Forsk. and O. foetida Poir, under field conditions. Screening at hot spots in Morocco and Tunisia resulted in the identification of resistant accessions of wild Lathyrus species against the parasitic weed. The level of resistance to O. foetida was higher among wild species compared with O. crenata. Field results showed complete resistance for O. crenata and O. foetida by L. articulatus L. and moderate resistance by L. aphaca L. and L. ochrus (L.) DC. Resistance to O. crenata in L. sativus accessions was validated in a pot experiment under controlled conditions. Two accessions—namely, IG64782 and IG65197—showed complete resistance to O. crenata. A moderately resistant accession, IG116989, that revealed low infestation in the field showed high susceptibility in pot experiment. The results indicated that the resistance against O. crenata and O. foetida was associated with slow development of the established tubercles and low induction of parasite germination.

Culturable endophytic bacteria from Phelipanche ramosa (Orobanchaceae) seeds

AbstractEndophytic microbiomes play a beneficial role in the development and protection of plants. However, seed-borne endophytic bacteria have not yet been fully explored. Investigation of parasitic plants, whose existence depends on yet poorly understood and complicated relationships with microorganisms and hosts, is particularly crucial. Endophytic bacteria promote seed conservation and facilitate seed germination in soil. Several root holoparasites from the Orobanchaceae family are the most aggressive broomrape species, often causing serious yield losses in important crops. Parasitic plants are characterized by the production of a large number of some of the smallest seeds in the world's flora, allowing them to stay viable in the soil for several dozen years. This study's aim was to isolate and characterize the seed endophyte and surface bacteria of the most aggressive and widespread broomrape weed, Phelipanche ramosa. We isolated two endophytic bacteria from within the seeds which are closely related to Brevibacterium frigoritolerans and Bacillus simplex described as soil bacteria, highly resistant to environmental conditions, and as plant growth-promoting rhizobacteria. Moreover, we isolated three strains from the surface of non-sterile seeds; all three isolates were related to the Bacillus cereus group.

The problem of Orobanche spp. and Phelipanche spp. and their management in Iran

AbstractBroomrape species (Orobanche spp. and Phelipanche spp.) pose a tremendous threat to economically important crops in Iran; however, there is little information on the country’s major broomrape species, their distribution and host ranges, and the subsequent crop losses they cause. The literature from Iran describes Egyptian broomrape (Orobanche aegyptiaca Pers.), hemp broomrape (Orobanche ramosa L.), Phelipanche nana (Reut.) Beck, and Orobanche cumana Wallr. as the major species of broomrape infesting agricultural fields. Solanaceae crops are among the most susceptible crops to infestation by broomrape in the country, and farmers are either shifting production to crops with lesser value or abandoning crop production entirely. Among infested crops, tomato (Solanum lycopersicum L.) is the most susceptible and widely infested, resulting in annual crop yield reductions of up to 40%. Chick pea (Cicer arietinum L.) and canola (Brassica napus L.) are also highly susceptible to broomrape infestation. Current control methods (physical, agronomical, biological, and chemical) have not proven to be effective or economic. The microscopic size of broomrape seeds and the presence of a wide range of host plants (weeds and crops) have promoted the spread of broomrape to new areas of Iran. Hence, the familiarization of farmers with the biology of broomrape would be highly effective in finding suitable control measures and in preventing its further distribution.

Broomrape Threat to Agriculture

The broomrapes are plants that have modified their biology to feed on roots of other plants, emerging above the soil only to flower. There are about 150 broomrape species, most of which infect wild plants in natural habitats without causing economic problems. However, a few of them have adapted to agricultural ecosystems becoming troublesome root parasitic weeds. The most damaging ones are Orobanche cernua, O. crenata, O. cumana, O. minor, Phelipanche aegyptiaca and P. ramosa all of which severely constrain important dicot crops in Africa, Asia, and Europe. They are continuously extending to new areas, showing an ability to evolve thereby enlarging their host ranges, adapting to new areas and overcoming resistances introduced by the breeder. As flowering plants disseminated by seeds, broomrape distribution and management (containment, sanitation, cultural practices, and biological and chemical control) fall under the purview of weed science. However, broomrapes differ from standard weeds as they behave as pathogens that attach to host roots to feed on them. As for any other disease, the host plants might protect themselves by defence mechanisms that can be selected by plant breeders to develop resistant cultivars. In spite of these efforts, rather than being contained, the broomrape threat is increasing, not only extending to new suitable areas but also adapting genetically to infect new crops and to increase virulence.

A Two-Year Simulated Crop Rotation Confirmed the Differential Infestation of Broomrape Species in China Is Associated with Crop-Based Biostimulants

In Yanqi County of Xinjiang Uygur Autonomous Region, China, broomrape species (Orobanche cumana Wallr and Phelipanche aegyptiaca Pers.) contribute to significant losses of processing tomato and sunflower. During the past decades, a significant infestation pattern was observed between these broomrape species with no scientific peer-reviewed explanation. A two-year pot experiment simulating the crop rotation and an independent hydroponic experiment were performed to address the problem and indicate the main reason behind the differential infestation pattern. Different varieties of three crops (sugar beet, pepper, and wheat) were grown in rotation with tomato and sunflower to identify a crop-rotation induced control mechanism on these two broomrape species. Germination bioassays were performed in vitro to identify stimulation of plant biochemicals collected as methanolic shoots/roots extracts and root exudates on the germination patterns of broomrape seeds. Results indicated that sunflower broomrape soil seed banks reduced during the two-year crop rotation; however, Egyptian broomrape seed banks did not alter and the resulting parasitism significantly reduced tomato growth. Seed germination bioassays confirmed that the methanolic shoot/root extracts successfully stimulate sunflower broomrape seeds germination but fail to stimulate Egyptian broomrape seeds germination. Root exudates collected from hydroponically grown crops also confirmed differential germination patterns in both broomrape species. Current results are of vital importance to explain the control effect of a crop rotation system and moreover, lay the foundation to study the genetic evolution of broomrape species that results in their differential germination responses to natural stimuli.

Identification and occurrence of phenylethanoid and iridoid glycosides in six Polish broomrapes (Orobanche spp. and Phelipanche spp., Orobanchaceae)

There are about 200 holoparasitic broomrapes (Orobanchaceae) known worldwide, however, only several species have been so far investigated phytochemically. Among Orobanche s.l. are both rare and endangered species, as well as onerous crop pests. This study aims to give a phytochemical description, both qualitative and quantitative, of six broomrape species (Orobanche and Phelipanche taxa) growing in Poland, including species that have not been tested in detail (O. caryophyllacea, O. lutea, O. picridis, and P. arenaria). Sixteen metabolites, including 14 phenylethanoid glycosides (PhGs) and 2 iridoid glycosides (IrGs), were isolated and identified using NMR spectroscopy and hydrolysis, revealing the presence of two previously undescribed PhGs in P. ramosa, named ramoside A and 2′-acetylramoside A. In addition, in the example of O. caryophyllacea, we have reported as the first occurrence of IrGs in broomrapes. Concentrations of phenylethanoids, the main constituents of broomrapes, in the studied plant material (flowering shoots with haustoria) were determined using the UHPLC-PDA method. It was found that P. ramosa has been the richest source of PhGs. In addition, the differences between broomrapes have been visualized using principal component and cluster analysis. The results of the antiradical DPPH test of 13 PhGs confirmed previous findings on the relation of the antioxidant potential with the structure of phenolic moieties – phenolic acid and phenylethanoid unit.