Orobanche minor

Orobanche minor, the hellroot,[1] common broomrape, lesser broomrape, small broomrape or clover broomrape, is a holoparasitic flowering plant belonging to the genus Orobanche; a genus of about 150 non-photosynthetic plants that parasitize other autotrophic plants.

Orobanche minor
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Lamiales
Family: Orobanchaceae
Genus: Orobanche
Species:
O. minor
Binomial name
Orobanche minor

Characteristics and growth requirements

Orobanche minor grows to 0.5 m (1 ft 8 in) and is a perennial. The flowers are hermaphrodite.

Common broomrape grows in a wide variety of soils, namely moist, light (sandy), medium (loamy) and heavy (clay) soils that are acid, neutral or basic. It can grow in semi-shade or in full sunlight.[2]

The species appears in a wide range of colours from red-brown, yellow-brown to purple. Yellow specimens are also not uncommon and it is this extreme variability that makes identification on the basis of size or colour uncertain.[3] It is parasitic on various members of the pea (Fabaceae) and daisy (Asteraceae) families. Although widespread, its appearance is sporadic; despite this, it can occur in vast colonies from time to time. The main flowering season in the northern hemisphere is from May until the end of August and from August to January in the southern hemisphere.[4] The species has efficient seed dispersal and is largely inbreeding so that populations preferentially parasitizing a particular species which has its own clear ecological preferences may become effectively isolated and eventually may produce distinct taxa.[5]

The plants are attached to their host by means of haustoria, which transfer nutrients from the host to the parasite. Only the hemiparasitic species possess an additional extensive root system. The root system is reduced as its function is mainly anchorage of the plant.

Distribution

Common broomrape is one of the most widespread species, and is native to Southern Europe,[6] but has been widely introduced elsewhere, for example in the United States.[7] In New Zealand it is the only species of the genus present where it is regarded as an agricultural pest.[4] In the United Kingdom it is widely recorded in southern England, less common in Wales, rarely recorded in lowland Scotland and absent from the Highlands and outer islands.[8]

Taxonomy

Phylogenetic analyses have placed this species in the taxonomically difficult Minores species complex.[9][10] Four infraspecific taxa of Common broomrape are currently recognised in the United Kingdom: O. minor var. minor, O. minor var. flava, O. minor var. compositarum and O. minor subsp. maritima.[11][12] Chromosome No.: 2n = 38. The genetic structure of populations of O. minor are under investigation using molecular markers and DNA sequencing to help resolve the taxonomic and nomenclatural problems that have historically been linked with this species.[13]

Hosts and speciation
Entirely yellow O. minor colony

The common broomrape is highly generalist in its host range, and can infect hundreds of species in families from the Ranunculaceae to the Poaceae (=Gramineae) but with a clear preference for the Fabaceae (=Leguminosae) and Asteraceae (=Compositae).[11] However races occurring on different species of host are genetically divergent[14] and physiologically adapted to their local hosts, and may therefore be in a state of incipient speciation.[15] Urgent conservation efforts are required as the survival of some intraspecific taxa is very uncertain.[13]

References
  1. "Orobanche minor". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 25 July 2015.
  2. Plants for a Future Retrieved: 2011-08-07
  3. First Nature Archived 2011-09-29 at the Wayback Machine Retrieved: 2011-08-07
  4. "Broomrape". AgPest New Zealand. Retrieved 1 December 2016.
  5. Watsonia Retrieved: 2011-08-07
  6. Kreutz, C.A.J. (1995) Orobanche: Die Sommerwurzarten Europas. Maastricht: Stichting Natuurpublicaties (Limburg, Germany).
  7. Eizenberg, H.; Colquhoun, JB.; Mallory-Smith, C.A. (2003). "Variation in clover response to small broomrape (Orobanche minor)". Weed Science. 51 (5): 759–763. doi:10.1614/ws-03-029r. S2CID 86330666.
  8. NBN Gateway Retrieved: 2011-08-08
  9. Manen, JF; Habashi, C; Jeanmonod, D; Park, JM; Schneeweiss, GM (2004). "Phylogeny and intraspecific variability of holoparasitic Orobanche (Orobanchaceae) inferred from plastid rbcL sequences". Molecular Phylogenetics and Evolution. 33 (2): 482–500. doi:10.1016/j.ympev.2004.06.010. PMID 15336681.
  10. Schneeweiss, G.M.; Colwell, A.; Park, J-M.; Jang, C-G.; Stuessy, T.F. (2004). "Phylogeny of holoparasitic Orobanche (Orobanchaceae) inferred from nuclear ITS sequences". Molecular Phylogenetics and Evolution. 30 (2): 465–478. doi:10.1016/s1055-7903(03)00210-0. PMID 14715236.
  11. Rumsey, F.J.; Jury, S (1991). "An account of Orobanche L. in Britain and Ireland". Watsonia. 18: 257–295.
  12. Rumsey, F.J. (2007). "A reconsideration of Orobanche maritima Pugsley (Orobanchaceae) and related taxa in southern England and the Channel Islands". Watsonia. 26: 473–476.
  13. BSBI Retrieved: 2011-08-07
  14. Thorogood, C.J.; Rumsey, F.J.; Harris, S; Hiscock, S.J. (2008). "Host-driven divergence in the parasitic plant Orobanche minor Sm. (Orobanchaceae)". Molecular Ecology. 17 (19): 4289–4303. doi:10.1111/j.1365-294x.2008.03915.x. PMID 19378406. S2CID 42331081.
  15. Thorogood, C.J.; Rumsey, F.J.; Hiscock, S.J. (2009). "Host-specific races in the holoparasitic angiosperm Orobanche minor: implications for speciation in parasitic plants". Annals of Botany. 103 (7): 1005–1014. doi:10.1093/aob/mcp034. PMC 2707918. PMID 19251714.

Further reading
  • Cimino, Alessio; Basso, Sara; Andolfi, Anna (1 October 2014). "Effect of Fungal and Plant Metabolites on Broomrapes (Orobanche and Phelipanche spp.) Seed Germination and Radicle Growth". Journal of Agricultural and Food Chemistry. 62 (43): 10485–10492. doi:10.1021/jf504609w. PMID 25272312.
  • Mallory-Smith, Carol; Colquhoun, Jed (October 7, 2011). "Small Broomrape (Orobanche minor) in Oregon and the 3 Rs: Regulation, Research, and Reality". Weed Science. 63 (1): 277–282. doi:10.1614/WS-D-11-00078.1. S2CID 86599728.
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