Striga

Striga
	Striga bilabiata
Systematics
	Nuclear eudicotyledons
	Asterids
	Euasterids I
Order :	Mint family (Lamiales)
Family :	Summer root family (Orobanchaceae)
Genre :	Striga
Scientific name
	Striga
	Lour.

Striga is a genus in the family of Broomrape family (Orobanchaceae). The Striga species are full parasites mostly on sweet grass species, including economically important cereal species . They are common in the tropics to subtropics of the Old World.

description

Illustration from Exotic Flora , plate 203 by Striga asiatica

Vegetative characteristics

Striga species are usually annual, herbaceous plants that are rarely perennial . They are root parasites . The root system is greatly reduced, adventitious roots emerge from scales above the earth , which end in a small haustorium , usually 1 to 2 mm in diameter . In some species there are also primary houses up to 5 cm in size . The perennial species form underground rhizomes or tubers , from whose scale leaves new shoots emerge every year. The above-ground parts of the plant are bristly or scaly hairy ( indument ).

The stem axis stands stiffly upright, is green or gray in color and has a square and ribbed cross-section, square and rounded or twisting at the edges. Purely vegetative shoot axes are not formed, as the plants are not dependent on the function of the leaves due to the parasitism . That is, each branch of the stem axis forms an inflorescence .

The leaves are opposite or almost opposite, they are complete or almost sessile. Near the base of the shoot, they are reduced to small scales in most species.

The germination occurs hypogeous, the optimum germination temperature is between 30 and 40 ° C, below 15 ° C and 45 ° C is no germination. The seedlings are free of chlorophyll and are scaled.

Inflorescences and flowers

The flowers are in the axils of the leaves in spike-like or dense head-shaped inflorescences. The bracts are leaf-like or reduced, there are two bracts .

The hermaphrodite flowers are zygomorphic and five-fold with a double flower envelope . The calyx is tubular, five-lobed or provided with five (rarely four) teeth. In some species a vein can be seen between the sepal ribs. The crown is usually colored red or white, but there are also species with a salmon-colored, orange or yellow crown. The crown consists of a narrow corolla tube, which is followed by an enlarged, two-part crown hem. With a diameter of less than 1 mm, the opening of the corolla tube is very small and abundantly covered with trichomes . The upper lobes of the coronary hem are fused and stand upright, the lower three lobes are free and protruding.

The four stamens occur in two different lengths and start below the opening of the. The short stamens are at the base of the dust bag is fixed. The anthers are single-lobed, pollen is only sparsely formed and is often sticky. The pistil is tubular and forms a multitude of fine ovules . The stylus is round and elongated, the stigma is bilobed. At the base of the ovary is a nectary .

Fruits and seeds

On the cylindrical or almost egg-shaped capsule fruits that open in folds , the stylus is mostly permanent. The seeds are very fine (so-called "dust seeds" ) and have conspicuous ribs surrounding them. The embryo is small.

Locations and way of life

The Striga species tolerate a relatively wide range of environmental conditions. They grow in areas with annual rainfall between 25 and 150 cm.

More detailed studies of the host plant spectrum are lacking, only the effects on economically important plants are known. In general, the plants appear to have a narrower host of host choices compared to other closely related parasitic genera. Cereals are only attacked by Striga hermonthica and Striga asiatica . Dicotyledons such as legumes are preferred only by the worldwide common Striga gesnerioides and the two similar, small-scale species Striga gastonii and Striga lepidagathidis .

Striga as a pest

Striga is considered to be the greatest enemy of food production in the savannah areas of Africa, where around 100 million hectares are potentially affected. Gebisa Ejeta received the World Food Prize in 2009 for breeding a Striga- tolerant Sorghum variety .

By jointly sowing grain with silver cinderella ( Celosia argentea ), Striga species in Uganda could be kept away from fields and the yield increased considerably.

Striga can no longer be effectively combated with herbicides after the emergence . 2,4-D and dicamba are effective but cannot be used in dicotyledonous crops.

Systematics and distribution

The genus Striga was established in 1790 by João de Loureiro in Flora Cochinchinensis , 1, page 22. Type species is Striga lutea Lour. The scientific name of the genus Striga is derived from the Latin striga (= old witch ), which in turn is derived from the ancient Greek στρίγξ from στρίζω = τρίζω (= the eared owl). The name is probably due to the fact that the infestation of crops often remains undetected at first and is only noticed when the parasitic plant blooms, i.e. when the greatest damage has already occurred.

The genus Striga contains 34 to 35 species. A division of the genus into two sections was proposed by Richard Wettstein in 1891 , he placed the species with a five-ribbed calyx in a section Pentapleurae and all other species with mostly ten calyx ribs in a section Polypleurae . However, it was later established that the number of calyx ribs can also vary within a species, but this division according to morphological aspects has so far been the only attempt to divide the genus. A third section Tetrosepalum was introduced by Adolf Engler in 1897 , which only contained the species Striga baumannii . This species differs significantly from the other species of the genus in several characteristics (root bulbs, woody calyx) and probably represents a genus of its own.

The genus Striga is common in the tropics and subtropics of the Old World, with a distribution center in Africa . In the New World, individual species are in neophytes .

There are 34 to 35 species in the Striga genus :

Habitus and flowers of Striga gesnerioides

Striga aequinoctialis A. Chev. ex Hutch. & Dalz. : It occurs in Ivory Coast , Liberia , Guinea and Sierra Leone .
Striga angolensis Mohamed & Musselman : It occurs in Angola .
Striga angustifolia (D.Don) CJSaldanha : It occurs in tropical Africa, in tropical Asia, in Oman and on Hainan .
Striga asiatica (L.) Kuntze : It iswidespreadfrom tropical to southern Africa, on the Arabian Peninsula, in Madagascar and Mauritius , in tropical Asia, in China. She is a neophyte in Queensland.
Striga aspera (Willd.) Benth. : It occurs in tropical Africa.
Striga baumannii Engl .: Perhaps it belongs to a genus of its own.
Striga bilabiata (Thunb.) Kuntze : It occurs with six subspecies in tropical and southern Africa.
Striga brachycalyx Skan : It occurs in tropical Africa.
Striga chrysantha A.Raynal : It occurs in the Democratic Republic of the Congo and in the Central African Republic.
Striga curviflora (R.Br.) Benth. : It occurs in New Guinea and Australia .
Striga dalzielii Hutch. : It occurs in Mali , Guinea and Nigeria .
Striga densiflora (Benth.) Benth. : It occurs in Pakistan , India and Yunnan .
Striga elegans Benth. : It occurs from tropical to southern Africa.
Striga forbesii Benth. : It is distributed from tropical to southern Africa, to the South African provinces of Gauteng , KwaZulu-Natal , Limpopo , Mpumalanga as well as North West and Madagascar.
Striga gastonii A.Raynal : It occurs in Chad and the Central African Republic.
Striga gesnerioides (Willd.) Vatke : It occurs in Africa, on the Cape Verde Islands , on the Arabian Peninsula, in Pakistan, India, Nepal and Sri Lanka .
Striga gracillima H.Melchior : It occurs in Tanzania , Malawi and Zambia .

Striga hallaei A.Raynal : It occurs in Gabon and in the Democratic Republic of the Congo.
Striga hermonthica (Delile) Benth. : It occurs in Africa, the Arabian Peninsula and Madagascar.
Striga hirsuta Benth. : It occurs in tropical Africa and the Seychelles .
Striga junodii Schinz : It occurs in Mozambique , Mpumalanga and KwaZulu-Natal.
Striga klingii (Engl.) Skan : It occurs in tropical Africa.
Striga latericea Vatke : It occurs in Ethiopia , Somalia , Sudan , Kenya and Tanzania .
Striga lepidagathidis A. Raynal : It occurs in Senegal , Guinea and Guinea-Bissau .
Striga lutea Lour. : It occurs in tropical Africa, tropical Asia, China and Taiwan.
Striga macrantha (Benth.) Benth. : It occurs in tropical Africa.
Striga masuria (Buch.-Ham. Ex Benth.) Benth. : It occurs in India, Indochina , China, Taiwan and the Philippines .
Striga multiflora Benth. : It occurs in Indonesia , Australia and Luzon .
Striga parviflora Benth. : It occurs in the Australian states of Queensland and Northern Territory .
Striga passargei Engl .: It occurs in tropical Africa, Namibia and Yemen .
Striga pinnatifida Getachew Aweke : It occurs in Ethiopia .
Striga primuloides Chev. : It occurs in Ivory Coast , Mali , Ghana and Nigeria .
Striga pubiflora Klotzsch : It occurs in Kenya, Tanzania, Malawi and Mozambique.
Striga sulphurea Dalz. ex Dalz. & Gibbs : It occurs in India.
Striga yemenica Musselman & Heppner : It occurs in Ethiopia and Yemen.

swell

literature

D. Philcox: Striga. In: Flora Zambesiaca , Volume 8, Part 2, Royal Botanic Gardens, Kew. text same online as the printed work.
Kamal I. Mohamed, Lytton John Musselman and Charles R. Riches: The Genus Striga (Scrophulariaceae) in Africa . In: Annals of the Missouri Botanical Garden , Volume 88, Number 1, Winter 2001. Pages 60-103.

Individual evidence

↑ ^a ^b ^c D. Philcox: Striga. In: Flora Zambesiaca , Volume 8, Part 2, 1990, Royal Botanic Gardens, Kew. text same online as the printed work.
↑ ^a ^b Gebisa Ejeta: The Striga Scourge in Africa: A Growing Pandemic , Chapter 1 from Integrating New Technologies for Striga Control (2007)
↑ worldfoodprize.org: Sorghum Breeding and Conquering Striga .
↑ JR Olupot et al .: The effectiveness of Celosia argentia (Striga chaser) to control Striga on sorghum in Uganda. Crop Protection 22 / - / 2003. Pp. 463-468. PDF.
^ GD Odhiambo, JK Ransom: Effect of Dicamba on the Control of Striga hermonthica in Maize in Western Kenya . In: African Crop Science Journal . tape 1 , no. 2 , 1993, doi : 10.4314 / acsj.v1i2.69897 ( PDF ).
↑ University of Hohenheim: Various chemical control measures for controlling phytoparasites .
↑ ^a ^b Striga at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed January 26, 2018.
↑ ^a ^b Kamal I. Mohamed, Lytton John Musselman, Charles R. Riches: The Genus Striga (Scrophulariaceae) in Africa. In: Annals of the Missouri Botanical Garden , Volume 88, Number 1, 2001, pages 60-103.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w ^x ^y ^z ^aa ^ab ^ac ^ad ^ae ^af ^ag ^ah Striga in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved January 26, 2018.
↑ ^a ^b Species list for Striga in the Red List of South African Plants

Web links

Commons : Striga - collection of images, videos and audio files

Map with all linked sites: OSM | WikiMap

[FloraZambesiaca-1] D. Philcox: Striga. In: Flora Zambesiaca , Volume 8, Part 2, 1990, Royal Botanic Gardens, Kew. text same online as the printed work.

[Ejeta2007-2] Gebisa Ejeta: The Striga Scourge in Africa: A Growing Pandemic , Chapter 1 from Integrating New Technologies for Striga Control (2007)

[3] worldfoodprize.org: Sorghum Breeding and Conquering Striga .

[4] JR Olupot et al .: The effectiveness of Celosia argentia (Striga chaser) to control Striga on sorghum in Uganda. Crop Protection 22 / - / 2003. Pp. 463-468. PDF.

[Odhiambo1993-5] GD Odhiambo, JK Ransom: Effect of Dicamba on the Control of Striga hermonthica in Maize in Western Kenya . In: African Crop Science Journal . tape 1 , no. 2 , 1993, doi : 10.4314 / acsj.v1i2.69897 ( PDF ).

[6] University of Hohenheim: Various chemical control measures for controlling phytoparasites .

[Tropicos-7] Striga at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed January 26, 2018.

[Mohamed01a-8] Kamal I. Mohamed, Lytton John Musselman, Charles R. Riches: The Genus Striga (Scrophulariaceae) in Africa. In: Annals of the Missouri Botanical Garden , Volume 88, Number 1, 2001, pages 60-103.

[GRIN-9] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w ^x ^y ^z ^aa ^ab ^ac ^ad ^ae ^af ^ag ^ah Striga in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved January 26, 2018.

[RedListSA-10] Species list for Striga in the Red List of South African Plants