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54-633: Striga , commonly known as witchweed , is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae , although older classifications place it in the Scrophulariaceae . Some species are serious pathogens of cereal crops, with the greatest effects being in savanna agriculture in Africa. It also causes considerable crop losses in other regions, including other tropical and subtropical crops in its native range and in

108-557: A species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in the nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

162-441: A larva. The common brimstone , found across a broad geographic range, overwinters for 7 months to wait for the development of their larval host plants. Another unique butterfly, the large white , will only overwinter in southern Eurasia; they are not seen overwintering elsewhere. Some species of parasitic conopid flies, such as P. tibialis , are known to overwinter inside of the corpse of their bee/wasp hosts before emerging in

216-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

270-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

324-503: A number of rice cultivars, including some cultivars of NERICA (New Rice for Africa), effective pre- and post- attachment resistance mechanisms have been identified. 'StrigAway'™ herbicide-resistant, herbicide impregnated maize has been shown to reduce the seed bank by 30% in two seasons. Maize, sorghum, and sugarcane crops affected by witchweed in the United States have an estimated value well over $ 20 billion. Furthermore, witchweed

378-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

432-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

486-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

540-460: Is capable of producing between 90,000 and 500,000 seeds, which may remain viable in the soil for over 10 years. Most seeds produced are not viable. An annual plant, witchweed overwinters in the seed stage. Its seeds germinate in the presence of host root exudate , and develop haustoria which penetrate host root cells. Host root exudate contain strigolactones , signaling molecules that promote Striga seed germination. A bell-like swelling forms where

594-525: Is capable of wiping out an entire crop. It is so prolific that in 1957 the US Congress allocated money in an attempt to eradicate witchweed. Because of Striga , the Animal and Plant Health Inspection Service ( APHIS ) of the U.S. Department of Agriculture established a research station and control methods. Through infestation mapping, quarantine, and control activities such as contaminated seed destruction,

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648-402: Is characterized not necessarily by cold but by dry conditions; passing through such periods could likewise be called overwintering. Hibernation and migration are the two major ways in which overwintering is accomplished. Animals may also go into a state of reduced physiological activity known as torpor . Overwintering occurs in several classes of lifeform. In entomology , overwintering

702-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

756-413: Is how an insect passes the winter season. Many insects overwinter as adults, pupae , or eggs. This can be done inside buildings, under tree bark, or beneath fallen leaves or other plant matter on the ground, among other places. All such overwintering sites shield the insect from adverse conditions associated with winter. Activity almost completely ceases until conditions become more favourable. One example

810-595: Is more readily available, in Europe for example common crane and white storks . Some birds, however, such as black-capped chickadees , Golden-crowned kinglets , woodpeckers , and corvids , instead remain in colder areas throughout the winter, often remaining in groups for warmth. Plants are sometimes said to overwinter. At such times, growth of vegetative tissues and reproductive structures becomes minimal or ceases completely. For plants, overwintering often involves restricted water supplies and reduced light exposure. In

864-514: Is necessary to plant uncontaminated seeds and to clean soil and plant debris off of machinery, shoes, clothing, and tools before entering fields. If populations are low, hand weeding before seeds are produced is an option. Striga in the United States has been controlled through the use of several management strategies, including quarantines imposed on affected areas, control of movement of farm equipment between infected and uninfected areas, herbicide application, and imposed "suicidal germination". For

918-489: Is not growing, by transferring to an alternative host, living freely in the soil or surviving on plant refuse such as discarded potatoes. People are also described from time to time as overwintering. This was especially true in the past during the exploration of the planet when people had to pass the winter in places not ideally suited for winter survival, and even today in the polar regions . Today people may be said to overwinter when they temporarily move to warmer areas during

972-825: Is produced, are proven tactics. Coating maize seeds with fungi or a herbicide also appears to be a promising approach. An example is TAN222, the " Striga -resistant" maize variety which is coated with the systemic herbicide imazapyr , to which it is resistant. Any witchweed seeds sprouting when this maize is in the seedling stage are poisoned when their haustoria embed in the seedling's roots. Several sorghum varieties have high levels of resistance in local conditions, including 'N-13', 'Framida', and 'Serena'. 'Buruma', 'Shibe', 'Okoa' and 'Serere 17' millet cultivars are considered to be resistant in Tanzania. Some maize varieties show partial resistance to witchweed, including 'Katumani' in Kenya. In

1026-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

1080-555: Is stimulated, the Striga seed sends out an initial root to probe the soil for the host root. The initial root secretes an oxidizing enzyme that digests the host root surface, releasing quinones . If the quinone product is at the appropriate concentrations, a haustorium will develop from the initial root. The haustorium grows toward the host root until it makes contact with the root surface, establishing parasitic contact in relatively short order. Within 12 hours of initial haustorium growth,

1134-427: Is the mourning cloak butterfly , which experiences advantages to overwintering in its desired locations by being one of the first butterflies to emerge after a cold winter. Another example are the eggs of the forest tent caterpillar moth which overwinter tightly packed on tree branches. Other insects, such as the monarch butterfly , migrate and overwinter in warmer areas. Additionally, the ghost moth overwinters as

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1188-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

1242-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

1296-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

1350-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

1404-749: The Americas. The generic name derives from Latin strī̆ga , "witch". Witchweeds are characterized by bright-green stems and leaves and small, brightly colored and attractive flowers. They are obligate hemiparasites of roots and require a living host for germination and initial development, though they can then survive on their own. The number of species is uncertain, but may exceed 40 by some counts. Although most species of Striga are not pathogens that affect agriculture, some species have devastating effects upon crops, particularly those planted by subsistence farmers . Crops most commonly affected are maize , sorghum , rice and sugarcane . Three species cause

1458-473: The French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or the scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of

1512-555: The acreage parasitized by witchweed has been reduced by 99% since its discovery in the United States. APHIS has even offered cash rewards those who identify and report the weed, and encourages landowners to check their own acreage. Parasitizing important economic plants, witchweed is one of the most destructive pathogens in Africa. Witchweed affects 40% of Africa's arable savanna region, resulting in up to $ 13 billion lost every year. Striga affects 40 million hectares (98,842,153 acres) of crops in sub-Saharan Africa alone. In parts of Africa,

1566-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

1620-551: The development of witchweed. These findings, while limited to the Carolinas in the United States, seem to suggest that the pathogen could successfully infect the massive corn crops of the American Midwest. Management of witchweed is difficult because the majority of its life cycle takes place below ground. If it is not detected before emergence, it is too late to reduce crop losses. To prevent witchweed from spreading it

1674-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

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1728-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

1782-416: The haustorium recognizes the host root and begins rapid cell division and elongation. The haustorium forms a wedge shape and uses mechanical force and chemical digestion to penetrate the host root, pushing the host cells out of the way. Within 48–72 hours, the haustorium has penetrated the host root cortex . Finger-like structures on the haustorium, called oscula (from Latin osculum , "little mouth") penetrate

1836-738: The host xylem and phloem, the Striga cotyledons emerge from the seed. Temperatures ranging from 30 to 35 °C (86 to 95 °F) in a moist environment are ideal for germination. Witchweed will not develop in temperatures below 20 °C (68 °F). Agricultural soils with a light texture and low nitrogen levels tend to favor development. Still, witchweed has demonstrated a wide tolerance for soil types if soil temperatures are favorably high. Seeds have been shown to survive in frozen soil of temperatures as low as −15 °C (5 °F), attesting to their aptitude as overwintering structures. Soil temperature, air temperature, photoperiod , soil type, and soil nutrient and moisture levels do not greatly deter

1890-428: The host xylem through pits in the membrane. The oscula then swell to secure their position within the xylem membrane. Striga sieve tubes develop along with the oscula. Shortly after the host xylem is penetrated, Striga sieve tubes develop and approach the host phloem within eight cells. This eight cell layer allows for nonspecific nutrient transport from the host to the Striga seedling. Within 24 hours after tapping

1944-432: The idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but

1998-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

2052-448: The latter, in fields not yet planted in crops, seeds present in the soil are induced to germinate by injecting Ethylene gas, which mimics the natural physiological response tied to host recognition. Because no host roots are available, the seedlings die. Unfortunately, each mature Striga plant can produce tens of thousands of tiny seeds, which may remain dormant in the soil for many years. Thus, such treatments do not remove all seeds from

2106-524: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Overwintering Overwintering is the process by which some organisms pass through or wait out the winter season , or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures , ice , snow , limited food supplies) make normal activity or even survival difficult or near impossible. In some cases "winter"

2160-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

2214-457: The most damage: Striga asiatica , S. gesnerioides , and S. hermonthica . Witchweed parasitizes maize, millet, sorghum, sugarcane, rice, legumes, and a range of weedy grasses. It is capable of significantly reducing yields, in some cases wiping out the entire crop. Host plant symptoms, such as stunting , wilting , and chlorosis , are similar to those seen from severe drought damage, nutrient deficiency, and vascular disease. Each plant

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2268-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

2322-409: The parasitic roots attach to the roots of the host. The pathogen develops underground, where it may spend the next four to seven weeks before emergence, when it rapidly flowers and produces seeds. Witchweed seeds spread readily via wind and water, and in soil via animal vectors. The chief means of dispersal, however, is through human activity, by means of machinery, tools, and clothing. Once germination

2376-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

2430-402: The soil. Moreover, this method is expensive and not generally available to farmers in developing nations of Africa and Asia. Another method called trap cropping involves planting a species in an infested field that will induce the Striga seeds to germinate but will not support attachment of the parasite. This method has been used in sorghum plantations by planting Celosia argentea between

2484-420: The sorghum rows. Cotton, sunflower and linseed are also effective trap crops. Planting silverleaf desmodium ( Desmodium uncinatum ), as is done in push-pull intercropping , inhibits Striga seed germination and has worked effectively intercropped with maize. Increasing nitrogen levels in the soil, growing Striga -tolerant varieties, trap-cropping, and planting susceptible crops harvested before witchweed seed

2538-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

2592-419: The spring following overwintering many plants will enter their flowering stage. Farmers and gardeners use a process of "overwintering" to achieve early spring harvests of some crops by planting annual or biennial species in fall, often under the protection of high or low tunnels. In plant pathology , overwintering is where a plant pathogen survives the winter, during which its normal crop host species

2646-477: The spring. The queens of the yellow-faced bumblebee ( Bombus vosnesenskii ) will over-winter, and then emerge early in the flight season to obtain the best available subterranean nests. Lastly, many species of Lasioglossum , including L. hemichalceum (which is a common sweat bee ), will overwinter in underground nests before emerging in the spring to start new colonies. Many birds migrate and then overwinter in regions where temperatures are warmer or food

2700-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

2754-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

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2808-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

2862-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

2916-603: The witchweed infestation is so severe that some farmers must relocate every few years. The majority of crops in Africa are grown by subsistence farmers who cannot afford expensive witchweed controls, who therefore suffer much as a result of this pathogen. The following species are recognised in the genus Striga : Genus The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including

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