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Suetsugu K, Hirota SK, Hsu TC, Kurogi S, Imamura A, Suyama Y. Monotropastrum kirishimense (Ericaceae), a new mycoheterotrophic plant from Japan based on multifaceted evidence. JOURNAL OF PLANT RESEARCH 2023; 136:3-18. [PMID: 36445504 PMCID: PMC9832082 DOI: 10.1007/s10265-022-01422-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 10/26/2022] [Indexed: 05/10/2023]
Abstract
Due to their reduced morphology, non-photosynthetic plants have been one of the most challenging groups to delimit to species level. The mycoheterotrophic genus Monotropastrum, with the monotypic species M. humile, has been a particularly taxonomically challenging group, owing to its highly reduced vegetative and root morphology. Using integrative species delimitation, we have focused on Japanese Monotropastrum, with a special focus on an unknown taxon with rosy pink petals and sepals. We investigated its flowering phenology, morphology, molecular identity, and associated fungi. Detailed morphological investigation has indicated that it can be distinguished from M. humile by its rosy pink tepals and sepals that are generally more numerous, elliptic, and constantly appressed to the petals throughout its flowering period, and by its obscure root balls that are unified with the surrounding soil, with root tips that hardly protrude. Based on genome-wide single-nucleotide polymorphisms, molecular data has provided clear genetic differentiation between this unknown taxon and M. humile. Monotropastrum humile and this taxon are associated with different Russula lineages, even when they are sympatric. Based on this multifaceted evidence, we describe this unknown taxon as the new species M. kirishimense. Assortative mating resulting from phenological differences has likely contributed to the persistent sympatry between these two species, with distinct mycorrhizal specificity.
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Affiliation(s)
- Kenji Suetsugu
- Department of Biology, Graduate School of Science, Kobe University, Kobe, 657-8501, Japan.
- The Institute for Advanced Research, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501, Japan.
| | - Shun K Hirota
- Field Science Center, Graduate School of Agricultural Science, Tohoku University, 232-3 Yomogida, Naruko-Onsen, Osaki, Miyagi, 989-6711, Japan
| | - Tian-Chuan Hsu
- Botanical Garden Division, Taiwan Forestry Research Institute, No. 53, Nanhai Rd., Taipei, 100, Taiwan
| | - Shuichi Kurogi
- Miyazaki Prefectural Museum of Nature and History, 2-4-4, Jingû, Miyazaki, 880-0053, Japan
| | - Akio Imamura
- Hokkaido University of Education, Sapporo, 002-8501, Japan
| | - Yoshihisa Suyama
- Field Science Center, Graduate School of Agricultural Science, Tohoku University, 232-3 Yomogida, Naruko-Onsen, Osaki, Miyagi, 989-6711, Japan
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Bendaoud F, Kim G, Larose H, Westwood JH, Zermane N, Haak DC. Genotyping‐by‐sequencing analysis of
Orobanche crenata
populations in Algeria reveals genetic differentiation. Ecol Evol 2022; 12:e8750. [PMID: 35356582 PMCID: PMC8948082 DOI: 10.1002/ece3.8750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 02/28/2022] [Accepted: 03/01/2022] [Indexed: 12/12/2022] Open
Abstract
Crenate broomrape (Orobanche crenata Forsk.) is a serious long‐standing parasitic weed problem in Algeria, mainly affecting legumes but also vegetable crops. Unresolved questions for parasitic weeds revolve around the extent to which these plants undergo local adaptation, especially with respect to host specialization, which would be expected to be a strong selective factor for obligate parasitic plants. In the present study, the genotyping‐by‐sequencing (GBS) approach was used to analyze genetic diversity and population structure of 10 Northern Algerian O. crenata populations with different geographical origins and host species (faba bean, pea, chickpea, carrot, and tomato). In total, 8004 high‐quality single‐nucleotide polymorphisms (5% missingness) were obtained and used across the study. Genetic diversity and relationships of 95 individuals from 10 populations were studied using model‐based ancestry analysis, principal components analysis, discriminant analysis of principal components, and phylogeny approaches. The genetic differentiation (FST) between pairs of populations was lower between adjacent populations and higher between geographically separated ones, but no support was found for isolation by distance. Further analyses identified four genetic clusters and revealed evidence of structuring among populations and, although confounded with location, among hosts. In the clearest example, O. crenata growing on pea had a SNP profile that was distinct from other host/location combinations. These results illustrate the importance and potential of GBS to reveal the dynamics of parasitic weed dispersal and population structure.
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Affiliation(s)
- Farah Bendaoud
- Department of Botany Ecole Nationale Supérieure Agronomique, ENSA Algiers Algeria
| | - Gunjune Kim
- Department of Plant Pathology, Physiology and Weed Science Virginia Tech Blacksburg Virginia USA
| | - Hailey Larose
- Department of Plant Pathology, Physiology and Weed Science Virginia Tech Blacksburg Virginia USA
| | - James H. Westwood
- Department of Plant Pathology, Physiology and Weed Science Virginia Tech Blacksburg Virginia USA
- School of Plant and Environmental Sciences Virginia Tech Blacksburg Virginia USA
| | - Nadjia Zermane
- Faculty of Sciences University of Algiers Algiers Algeria
| | - David C. Haak
- Department of Plant Pathology, Physiology and Weed Science Virginia Tech Blacksburg Virginia USA
- School of Plant and Environmental Sciences Virginia Tech Blacksburg Virginia USA
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Boukteb A, Sakaguchi S, Ichihashi Y, Kharrat M, Nagano AJ, Shirasu K, Bouhadida M. Analysis of Genetic Diversity and Population Structure of Orobanche foetida Populations From Tunisia Using RADseq. FRONTIERS IN PLANT SCIENCE 2021; 12:618245. [PMID: 33927733 PMCID: PMC8078179 DOI: 10.3389/fpls.2021.618245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/10/2021] [Indexed: 05/25/2023]
Abstract
Orobanche foetida Poiret is a holoparasitic plant that lacks chlorophyll and totally depending on its host for its growth. Orobanche foetida parasitizes host plant roots and extract nutrient and water via a haustorium. Although O. foetida distributes in the Mediterranean region as a wild plant parasite, it parasitizes faba bean causing serious damages which may reach 90% yield losses in Tunisia. Analysis of genetic diversity of the parasite is important to better understand its evolution and spread, remained largely unknown. In this work, we present the first study on genetic diversity and population structure using the robust technique Restriction-site-Associated DNA sequencing (RADseq) for Orobanche spp. We collected 244 samples of O. foetida from 18 faba bean fields in the north of Tunisia including 17 populations from the north-west and one population form the north-east. To overcome the difficulty of SNP discovery in O. foetida genome as a non-model and tetraploid plant, we utilized three different informatics pipelines, namely UNEAK, pyRAD and Stacks. This study showed that genetic differentiation occurred in the Tunisian O. foetida emphasizing the isolation by distance effect. However, no strong population clustering was detected in this work basing on the three data sets and clustering methods used. The present study shed the light on the current distribution and the genetic variation situation of the fetid broomrape in Tunisia, highlighting the importance of understanding the evolution of this parasite and its genetic background. This will aid in developing efficient strategies to control this parasite and its expansion in Tunisia and worldwide.
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Affiliation(s)
- Amal Boukteb
- Faculty of Science of Tunis, University of Tunis El Manar, Tunis, Tunisia
- Field Crop Laboratory, National Institute of Agricultural Research of Tunisia, Carthage University, Tunis, Tunisia
| | - Shota Sakaguchi
- Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | | | - Mohamed Kharrat
- Field Crop Laboratory, National Institute of Agricultural Research of Tunisia, Carthage University, Tunis, Tunisia
| | | | - Ken Shirasu
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | - Mariem Bouhadida
- Field Crop Laboratory, National Institute of Agricultural Research of Tunisia, Carthage University, Tunis, Tunisia
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Guo X, Zhao Z, Mar SS, Zhang D, Saunders RMK. A symbiotic balancing act: arbuscular mycorrhizal specificity and specialist fungus gnat pollination in the mycoheterotrophic genus Thismia (Thismiaceae). ANNALS OF BOTANY 2019; 124:331-342. [PMID: 31189014 PMCID: PMC6758588 DOI: 10.1093/aob/mcz087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 05/17/2019] [Indexed: 05/25/2023]
Abstract
BACKGROUND AND AIMS Mycorrhizal associations in mycoheterotrophic plants are generally more specialized than in autotrophs. Mycoheterotrophs typically bear small, inconspicuous flowers that often self-pollinate to maximize seed set, although some have structurally complex flowers indicative of xenogamy. A trade-off has previously been proposed between specialization in these above- and below-ground symbioses, although empirical data are lacking. METHODS We used next-generation DNA sequencing to compare the mycorrhizal communities from the roots of a mycoheterotrophic species, Thismia tentaculata (Thismiaceae), and its neighbouring autotrophs. We furthermore conducted detailed assessments of floral phenology and pollination ecology, and performed artificial pollination experiments to determine the breeding system. KEY RESULTS Thismia tentaculata maintains a symbiotic association with a single arbuscular mycorrhizal Rhizophagus species. The flowers are pollinated by a single species of fungus gnats (Corynoptera, Sciaridae), which are attracted by the yellow pigments and are temporarily restrained within the perianth chamber before departing via apertures between the anthers. The plants are self-compatible but predominantly xenogamous. CONCLUSIONS Our findings demonstrate that T. tentaculata maintains highly specialized associations with pollinators and mycorrhizal fungi, both of which are widely distributed. We suggest that specialization in multiple symbiotic interactions is possible in mycoheterotrophs if redundant selective pressures are not exerted to further restrict an already constrained suite of life-history traits.
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Affiliation(s)
- Xing Guo
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Zhongtao Zhao
- South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | | | - Dianxiang Zhang
- South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
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Yule KM, Bronstein JL. Reproductive ecology of a parasitic plant differs by host species: vector interactions and the maintenance of host races. Oecologia 2017; 186:471-482. [DOI: 10.1007/s00442-017-4038-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 12/04/2017] [Indexed: 12/21/2022]
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Schneider AC, Colwell AEL, Schneeweiss GM, Baldwin BG. Cryptic host-specific diversity among western hemisphere broomrapes (Orobanche s.l., Orobanchaceae). ANNALS OF BOTANY 2016; 118:1101-1111. [PMID: 27539600 PMCID: PMC5091723 DOI: 10.1093/aob/mcw158] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Revised: 06/06/2016] [Accepted: 06/24/2016] [Indexed: 06/01/2023]
Abstract
BACKGROUND AND AIMS The broomrapes, Orobanche sensu lato (Orobanchaceae), are common root parasites found across Eurasia, Africa and the Americas. All species native to the western hemisphere, recognized as Orobanche sections Gymnocaulis and Nothaphyllon, form a clade that has a centre of diversity in western North America, but also includes four disjunct species in central and southern South America. The wide ecological distribution coupled with moderate taxonomic diversity make this clade a valuable model system for studying the role, if any, of host-switching in driving the diversification of plant parasites. METHODS Two spacer regions of ribosomal nuclear DNA (ITS + ETS), three plastid regions and one low-copy nuclear gene were sampled from 163 exemplars of Orobanche from across the native geographic range in order to infer a detailed phylogeny. Together with comprehensive data on the parasites' native host ranges, associations between phylogenetic lineages and host specificity are tested. KEY RESULTS Within the two currently recognized species of O. sect. Gymnocaulis, seven strongly supported clades were found. While commonly sympatric, members of these clades each had unique host associations. Strong support for cryptic host-specific diversity was also found in sect. Nothaphyllon, while other taxonomic species were well supported. We also find strong evidence for multiple amphitropical dispersals from central North America into South America. CONCLUSIONS Host-switching is an important driver of diversification in western hemisphere broomrapes, where host specificity has been grossly underestimated. More broadly, host specificity and host-switching probably play fundamental roles in the speciation of parasitic plants.
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Affiliation(s)
- Adam C Schneider
- Department of Integrative Biology, 1005 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA
| | - Alison E L Colwell
- Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA
| | - Gerald M Schneeweiss
- Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria
| | - Bruce G Baldwin
- Department of Integrative Biology, 1005 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA Jepson Herbarium, 1001 Valley Life Sciences Building, University of California, Berkeley, CA 94720, USA
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Wang T, Wang Z, Xia F, Su Y. Local adaptation to temperature and precipitation in naturally fragmented populations of Cephalotaxus oliveri, an endangered conifer endemic to China. Sci Rep 2016; 6:25031. [PMID: 27113970 PMCID: PMC4844950 DOI: 10.1038/srep25031] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 04/04/2016] [Indexed: 01/02/2023] Open
Abstract
Cephalotaxus oliveri is an endangered tertiary relict conifer endemic to China. The species survives in a wide range from west to east with heterogeneous climatic conditions. Precipitation and temperature are main restrictive factors for distribution of C. oliveri. In order to comprehend the mechanism of adaptive evolution to climate variation, we employed ISSR markers to detect adaptive evolution loci, to identify the association between variation in temperature and precipitation and adaptive loci, and to investigate the genetic structure for 22 C. oliveri natural populations. In total, 14 outlier loci were identified, of which five were associated with temperature and precipitation. Among outlier loci, linkage disequilibrium (LD) was high (42.86%), which also provided strong evidence for selection. In addition, C. oliveri possessed high genetic variation (93.31%) and population differentiation, which may provide raw material to evolution and accelerate local adaptation, respectively. Ecological niche modeling showed that global warming will cause a shift for populations of C. oliveri from south to north with a shrinkage of southern areas. Our results contribute to understand the potential response of conifers to climatic changes, and provide new insights for conifer resource management and conservation strategies.
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Affiliation(s)
- Ting Wang
- College of Life Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Zhen Wang
- College of Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Fan Xia
- School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Yingjuan Su
- School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
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The genetic structure of wild Orobanche cumana Wallr. (Orobanchaceae) populations in eastern Bulgaria reflects introgressions from weedy populations. ScientificWorldJournal 2014; 2014:150432. [PMID: 25143963 PMCID: PMC4131075 DOI: 10.1155/2014/150432] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 06/17/2014] [Accepted: 07/01/2014] [Indexed: 02/01/2023] Open
Abstract
Orobanche cumana is a holoparasitic plant naturally distributed from central Asia to south-eastern Europe, where it parasitizes wild Asteraceae species. It is also an important parasitic weed of sunflower crops. The objective of this research was to investigate genetic diversity, population structure, and virulence on sunflower of O. cumana populations parasitizing wild plants in eastern Bulgaria. Fresh tissue of eight O. cumana populations and mature seeds of four of them were collected in situ on wild hosts. Genetic diversity and population structure were studied with SSR markers and compared to weedy populations. Two main gene pools were identified in Bulgarian populations, with most of the populations having intermediate characteristics. Cross-inoculation experiments revealed that O. cumana populations collected on wild species possessed similar ability to parasitize sunflower to those collected on sunflower. The results were explained on the basis of an effective genetic exchange between populations parasitizing sunflower crops and those parasitizing wild species. The occurrence of bidirectional gene flow may have an impact on wild populations, as new physiological races continuously emerge in weedy populations. Also, genetic variability of wild populations may favour the ability of weedy populations to overcome sunflower resistance mechanisms.
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Stoyanov K, Gevezova M, Denev I. Identification of ISSR Markers for Studying the Biodiversity of Bulgarian Representatives of GenusOrobancheSubsectionMinores. BIOTECHNOL BIOTEC EQ 2014. [DOI: 10.5504/bbeq.2011.0139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Bromham L, Cowman PF, Lanfear R. Parasitic plants have increased rates of molecular evolution across all three genomes. BMC Evol Biol 2013; 13:126. [PMID: 23782527 PMCID: PMC3694452 DOI: 10.1186/1471-2148-13-126] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 06/05/2013] [Indexed: 11/26/2022] Open
Abstract
Background Theoretical models and experimental evidence suggest that rates of molecular evolution could be raised in parasitic organisms compared to non-parasitic taxa. Parasitic plants provide an ideal test for these predictions, as there are at least a dozen independent origins of the parasitic lifestyle in angiosperms. Studies of a number of parasitic plant lineages have suggested faster rates of molecular evolution, but the results of some studies have been mixed. Comparative analysis of all parasitic plant lineages, including sequences from all three genomes, is needed to examine the generality of the relationship between rates of molecular evolution and parasitism in plants. Results We analysed DNA sequence data from the mitochondrial, nuclear and chloroplast genomes for 12 independent evolutionary origins of parasitism in angiosperms. We demonstrated that parasitic lineages have a faster rate of molecular evolution than their non-parasitic relatives in sequences for all three genomes, for both synonymous and nonsynonymous substitutions. Conclusions Our results prove that raised rates of molecular evolution are a general feature of parasitic plants, not confined to a few taxa or specific genes. We discuss possible causes for this relationship, including increased positive selection associated with host-parasite arms races, relaxed selection, reduced population size or repeated bottlenecks, increased mutation rates, and indirect causal links with generation time and body size. We find no evidence that faster rates are due to smaller effective populations sizes or changes in selection pressure. Instead, our results suggest that parasitic plants have a higher mutation rate than their close non-parasitic relatives. This may be due to a direct connection, where some aspect of the parasitic lifestyle drives the evolution of raised mutation rates. Alternatively, this pattern may be driven by an indirect connection between rates and parasitism: for example, parasitic plants tend to be smaller than their non-parasitic relatives, which may result in more cell generations per year, thus a higher rate of mutations arising from DNA copy errors per unit time. Demonstration that adoption of a parasitic lifestyle influences the rate of genomic evolution is relevant to attempts to infer molecular phylogenies of parasitic plants and to estimate their evolutionary divergence times using sequence data.
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Affiliation(s)
- Lindell Bromham
- Centre for Macroevolution and Macroecology, Research School of Biology, Australian National University, Canberra, A.C.T. 0200, Australia.
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Auger B, Pouvreau JB, Pouponneau K, Yoneyama K, Montiel G, Le Bizec B, Yoneyama K, Delavault P, Delourme R, Simier P. Germination stimulants of Phelipanche ramosa in the rhizosphere of Brassica napus are derived from the glucosinolate pathway. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:993-1004. [PMID: 22414435 DOI: 10.1094/mpmi-01-12-0006-r] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Phelipanche ramosa is a major parasitic weed of Brassica napus. The first step in a host-parasitic plant interaction is stimulation of parasite seed germination by compounds released from host roots. However, germination stimulants produced by B. napus have not been identified yet. In this study, we characterized the germination stimulants that accumulate in B. napus roots and are released into the rhizosphere. Eight glucosinolate-breakdown products were identified and quantified in B. napus roots by gas chromatography-mass spectrometry. Two (3-phenylpropanenitrile and 2-phenylethyl isothiocyanate [2-PEITC]) were identified in the B. napus rhizosphere. Among glucosinolate-breakdown products, P. ramosa germination was strongly and specifically triggered by isothiocyanates, indicating that 2-PEITC, in particular, plays a key role in the B. napus-P. ramosa interaction. Known strigolactones were not detected by ultraperformance liquid chromatography-tandem mass spectrometry, and seed of Phelipanche and Orobanche spp. that respond to strigolactones but not to isothiocyanates did not germinate in the rhizosphere of B. napus. Furthermore, both wild-type and strigolactone biosynthesis mutants of Arabidopsis thaliana Atccd7 and Atccd8 induced similar levels of P. ramosa seed germination, suggesting that compounds other than strigolactone function as germination stimulants for P. ramosa in other Brassicaceae spp. Our results open perspectives on the high adaptation potential of root-parasitic plants under host-driven selection pressures.
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Thorogood CJ, Hiscock SJ. Compatibility interactions at the cellular level provide the basis for host specificity in the parasitic plant Orobanche. THE NEW PHYTOLOGIST 2010; 186:571-575. [PMID: 20522165 DOI: 10.1111/j.1469-8137.2009.03173.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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Thorogood C, Hiscock S. Specific developmental pathways underlie host specificity in the parasitic plant Orobanche. PLANT SIGNALING & BEHAVIOR 2010; 5:275-277. [PMID: 20081361 PMCID: PMC2881276 DOI: 10.4161/psb.5.3.10660] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 11/14/2009] [Indexed: 05/28/2023]
Abstract
Parasitic angiosperms are an ecologically and economically important group of plants. However our understanding of the basis for host specificity in these plants is embryonic. Recently we investigated host specificity in the parasitic angiosperm Orobanche minor, and demonstrated that this host generalist parasite comprises genetically defined races that are physiologically adapted to specific hosts. Populations occurring naturally on red clover (Trifolium pratense) and sea carrot (Daucus carota subsp. gummifer) respectively, showed distinct patterns of host specificity at various developmental stages, and a higher fitness on their natural hosts, suggesting these races are locally adapted. Here we discuss the implications of our findings from a broader perspective. We suggest that differences in signal responsiveness and perception by the parasite, as well as qualitative differences in signal production by the host, may elicit host specificity in this parasitic plant. Together with our earlier demonstration that these O. minor races are genetically distinct based on molecular markers, our recent data provide a snapshot of speciation in action, driven by host specificity. Indeed, host specificity may be an underestimated catalyst for speciation in parasitic plants generally. We propose that identifying host specific races using physiological techniques will complement conventional molecular marker-based approaches to provide a framework for delineating evolutionary relationships among cryptic host-specific parasitic plants.
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Affiliation(s)
- Chris Thorogood
- School of Biological Sciences, University of Bristol, Bristol, UK.
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Costea M, Stefanovic S. Cuscuta jepsonii (Convolvulaceae): An invasive weed or an extinct endemic? AMERICAN JOURNAL OF BOTANY 2009; 96:1744-1750. [PMID: 21622360 DOI: 10.3732/ajb.0800425] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Despite their ecological significance, parasitic plants face more conservation challenges than do autotrophic plants. This is especially true for the groups that include weedy or invasive species such as Cuscuta. While approximately half of the Cuscuta (dodders) species may require conservation measures, the genus as a whole is sometimes posted on governmental lists of noxious or quarantine weeds. Our study challenges this stereotype and uses the case of C. jepsonii (Jepson's dodder) to illustrate the precarious biodiversity and conservation status faced by many dodder species. Until now, Jepson's dodder has been known only from its type collection. Consequently, its phylogenetic affinities, morphological variation, and ecology have remained unknown, and the species is currently ambiguously considered either synonymous to the invasive North American weed C. indecora or to an extinct endemic from California. Using molecular data from newly found collections, we infer that C. jepsonii belongs to C. californica species complex, instead of C. indecora clade. Also, we discuss the conservation of this species within the broader biological and ecological context of Cuscuta in general.
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Affiliation(s)
- Mihai Costea
- Department of Biology, Wilfrid Laurier University, 75 University Avenue W, Waterloo, Ontario N2L 3C5, Canada
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Thorogood CJ, Rumsey FJ, Hiscock SJ. Host-specific races in the holoparasitic angiosperm Orobanche minor: implications for speciation in parasitic plants. ANNALS OF BOTANY 2009; 103:1005-14. [PMID: 19251714 PMCID: PMC2707918 DOI: 10.1093/aob/mcp034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2008] [Revised: 12/03/2008] [Accepted: 01/09/2009] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Orobanche minor is a root-holoparasitic angiosperm that attacks a wide range of host species, including a number of commonly cultivated crops. The extent to which genetic divergence among natural populations of O. minor is influenced by host specificity has not been determined previously. Here, the host specificity of natural populations of O. minor is quantified for the first time, and evidence that this species may comprise distinct physiological races is provided. METHODS A tripartite approach was used to examine the physiological basis for the divergence of populations occurring on different hosts: (1) host-parasite interactions were cultivated in rhizotron bioassays in order to quantify the early stages of the infection and establishment processes; (2) using reciprocal-infection experiments, parasite races were cultivated on their natural and alien hosts, and their fitness determined in terms of biomass; and (3) the anatomy of the host-parasite interface was investigated using histochemical techniques, with a view to comparing the infection process on different hosts. KEY RESULTS Races occurring naturally on red clover (Trifolium pratense) and sea carrot (Daucus carota ssp. gummifer) showed distinct patterns of host specificity: parasites cultivated in cross-infection studies showed a higher fitness on their natural hosts, suggesting that races show local adaptation to specific hosts. In addition, histological evidence suggests that clover and carrot roots vary in their responses to infection. Different root anatomy and responses to infection may underpin a physiological basis for host specificity. CONCLUSIONS It is speculated that host specificity may isolate races of Orobanche on different hosts, accelerating divergence and ultimately speciation in this genus. The rapid life cycle and broad host range of O. minor make this species an ideal model with which to study the interactions of parasitic plants with their host associates.
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Affiliation(s)
- C. J. Thorogood
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
| | - F. J. Rumsey
- Department of Botany, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - S. J. Hiscock
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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