A rigid, scabrous, bluish-green, annual, parasititic herb with erect stems that are branched, quadrangular and grooved on each face. Leaves are thick, scabrous and hispid along the margins. Inflorescence is a spike bearing flowers with fragrant, pink corollas, acuminate bracts and hispid hairy margins. Fruit is a cylindrical or subovoidal, loculicidal capsule enclosing numerous seeds with prominent ridges.
Nile Valley North of Nubia (Location: Delta), Nile Valley North of Nubia, Nubia.
Widespread in dry regions of tropical Africa, Madagascar and Arabia.
On native and cultivated grasses, especially sugar-cane.
Annual.
Height: 20-50 cm.
Striga hermonthica, commonly known as purple witchweed[1] or giant witchweed, is a hemiparasitic plant[1] that belongs to the family Orobanchaceae. It is devastating to major crops such as sorghum (Sorghum bicolor) and rice (Oryza sativa).[2] In sub-Saharan Africa, apart from sorghum and rice, it also infests maize (Zea mays), pearl millet (Pennisetum glaucum), and sugar cane (Saccharum officinarum).[3]
Striga hermonthica has undergone horizontal gene transfer from Sorghum to its nuclear genome. The S. hermonthica gene, ShContig9483, is most like a Sorghum bicolor gene, and additionally shows significant but lesser similarity to a gene from Oryza sativa. It shows no similarity to any known eudicot gene.[2]
Purple witchweed infects a variety of grasses, and legumes in sub-saharan Africa including rice, maize, millet, sugarcane, and cowpea. The symptoms mimic that of drought or nutrient-deficiency symptoms. Chlorosis, wilt, and stunting result from witchweed’s ability to extract nutrients from its host. Pre-emergence symptoms are difficult to diagnose secondary to their similarity to general lack of nutrients. Once emergence of the plant has taken place, damage has become too severe to mitigate.[4]
Seeds of witchweed overwinter in the soil after they are dispersed by wind, water, animals, or human machinery.[5] When the environment is correct, and if the seed is within a few centimeters of the host root, it will begin to germinate. The germinating plant grows towards hormones, called strigolactones, released from the host root.[6][7] The plant grows up the concentration gradient of these strigolactones. In the absence of strigolactone, the seed will not germinate. Strigolactone knockout plants have been used in an attempt to prevent infection by avoiding germination.[7] Once in contact with the root, the witchweed produces a haustorium establishing a parasitic relationship with the plant. It remains underground for several weeks while extracting nutrients. The stem while underground is round and white. After this stage, it emerges from the ground and rapidly flowers and produces seeds. The flowers self pollinate before opening. After emergence, the plant can perform photosynthesis to augment its metabolic demands.[6]
Witchweed’s ideal temperature for germination is 30-35 °C. Below 20 °C, the seeds will not germinate. Seeds can survive freezing temperatures.[8] However, the longevity of the seed is debated. Most say that under ideal conditions, seeds can remain viable up to 14 years, but wet soils greatly decrease the resilience of the seeds. At most in one year, 74% of viable seeds were lost secondary to wet soil.[9]
Witchweed is historically among the hardest parasitic plants to control. Fusarium oxysporum may be used as a possible biocontrol of witchweed and its host specificity makes it a good candidate. This fungus is thought to infect the early vasculature of the Striga plant.[10] Applying native strains of Fusarium oxysporum has not shown adequate crop restoration. However, using strains selected for their ability to over-produce specific amino acids[11][12] has shown highly effective results. Data on 500 Striga-infested farms were obtained in paired plot trials over two growing seasons in 2014-2015, using hybrid seed and fertilizer compared to hybrid seed, fertilizer and FoxyT14 (a trio of the virulence-enhanced strains for Fusarium). Most (99.6%) of the farmers had equal or greater yield in their Foxy T14 plots relative to yield in their comparable farmer-practice plots without Foxy T14. The average maize yield in the March–June rains season was increased by 56.5% in Foxy T14 plots relative to the farmer-practice plots (p < 0.0001, pair-wise t-test). Approximately one third of the farmers doubled their yield in this test.[13] This technology development is called The Toothpick Project[14] based on mechanism used to deliver the fungal strains to smallholder farmers via a toothpick, where the farmer can make a fresh, on-farm inoculum by growing the fungal strains on cooked rice. The project is being launched in Kenya and a team of scientists in eleven other countries is working on isolating local strains for development.
Another potential solution to purple witchweed for millet and sorghum crops is herbicide priming. When herbicide-resistant seeds were soaked in herbicidal chemicals before planting, up to an 80% decrease in infestation occurred.[15] The use of nitrogen-rich fertilizers reduces the witchweed infection rate. Although the mechanism behind this is not fully understood, the abundance of nitrogen is thought to disrupt nitrogen reductase activity. This has a ripple effect, resulting in the dysregulation of the plant's light and dark cycle, resulting in the striga's death.[16]
In 2018, an essential protein for witchweed germination was found to consistently bind to molecules of the detergent Triton X-100, which appears to inhibit the germination of the striga seeds, preventing the natural strigolactones from binding to their usual substrate.[17]
Intercropping with Desmodium spp. as in push-pull agriculture has been shown to be highly effective in the suppression of Striga.[18] Allelochemicals released by roots of Desmodium lead to "suicidal germination" of Striga, thus reducing the seed bank in the soil.[19] It has also been proposed that synthetic strigolactones could be used in agriculture to induce the suicidal germination of Striga seeds.[20]
In the late 1990s, "21 million hectares of cereals in Africa were estimated to be infested by S. hermonthica, leading to an estimated annual grain loss of 4.1 million tons".[3]
Striga hermonthica, commonly known as purple witchweed or giant witchweed, is a hemiparasitic plant that belongs to the family Orobanchaceae. It is devastating to major crops such as sorghum (Sorghum bicolor) and rice (Oryza sativa). In sub-Saharan Africa, apart from sorghum and rice, it also infests maize (Zea mays), pearl millet (Pennisetum glaucum), and sugar cane (Saccharum officinarum).
Striga hermonthica has undergone horizontal gene transfer from Sorghum to its nuclear genome. The S. hermonthica gene, ShContig9483, is most like a Sorghum bicolor gene, and additionally shows significant but lesser similarity to a gene from Oryza sativa. It shows no similarity to any known eudicot gene.
Striga hermonthica est une espèce de plantes parasites herbacées annuelles appartenant au genre Striga de la famille des Scrophulariaceae, originaire des régions tropicales de l'Ancien Monde.
Comme d'autres espèces voisines, telles que Striga asiatica et Striga gesnerioides, c'est un parasite dévastant des cultures importantes, en particulier le sorgho (Sorghum bicolor) et le riz (Oryza sativa)[1]. En Afrique subsaharienne, outre le sorgho et le riz, elle infeste le maïs (Zea mays), le millet perle (Pennisetum glaucum) et la canne à sucre (Saccharum officinarum)[2]. À la fin des années 1990, on estimait à vingt-et-un millions d'hectares les surfaces de céréales infestées en Afrique par Striga hermonthica, ce qui conduisait à une perte de production estimée à 4,1 millions de tonnes[2].
Striga hemonthica a subi un transfert horizontal de gènes du Sorgho dans son génome nucléaire. Le gène ShContig9483 de Striga hermonthica est très semblable à un gène de Sorghum bicolor et présente une similarité significative mais moindre avec un gène du riz (Oryza sativa). Il ne présente pas de similarité avec aucun gène connu d'eudicotylédones[1].
L'aire de répartition de Striga hemonthica s'étend dans les régions tropicales principalement en Afrique, y compris Madagascar, et secondairement en Asie.
Les pays concernés sont les suivants[3] :
Striga hermonthica est connue pour parasiter des espèces de la famille des Poaceae (graminées)[3], en particulier le sorgho, le maïs, la canne à sucre et les millets (genre Panicum).
Toutefois, selon une étude réalisée au Soudan, cette plante peut aussi parasiter des espèces de la famille des Fabaceae telles que l'arachide, le niébé, le lablab et le soja, provoquant des diminutions de rendement sensibles sauf sur le soja. Les Striga hermonthica se développant sur les racines de ces espèces de légumineuses avaient cependant un développement très réduit (hauteur ne dépassant un centimètre) contrastant avec la vigueur des individus poussant aux dépens du sorgho[4].
Striga hermonthica est une espèce de plantes parasites herbacées annuelles appartenant au genre Striga de la famille des Scrophulariaceae, originaire des régions tropicales de l'Ancien Monde.
Comme d'autres espèces voisines, telles que Striga asiatica et Striga gesnerioides, c'est un parasite dévastant des cultures importantes, en particulier le sorgho (Sorghum bicolor) et le riz (Oryza sativa). En Afrique subsaharienne, outre le sorgho et le riz, elle infeste le maïs (Zea mays), le millet perle (Pennisetum glaucum) et la canne à sucre (Saccharum officinarum). À la fin des années 1990, on estimait à vingt-et-un millions d'hectares les surfaces de céréales infestées en Afrique par Striga hermonthica, ce qui conduisait à une perte de production estimée à 4,1 millions de tonnes.
Striga hemonthica a subi un transfert horizontal de gènes du Sorgho dans son génome nucléaire. Le gène ShContig9483 de Striga hermonthica est très semblable à un gène de Sorghum bicolor et présente une similarité significative mais moindre avec un gène du riz (Oryza sativa). Il ne présente pas de similarité avec aucun gène connu d'eudicotylédones.
Кореневий паразит. Рослина вкрита шорсткими волосками, слабо галузиться, висота стебла 35-60 см (крупніша від стриги жовтої). Листя лінійне, цільнокрає. Квіти великі, червоно-рожевого кольору, зібрані у довгі китиці. Насіння темно-коричневе.
Насіння утворюється у великій кількості (за різними данними від 40 — 450 тисяч насінин на одній рослині). У ґрунті насіння залишається життєздатним до 20 років.[1] Воно проростає лише після появи поруч коріння одного з хазяїнів рослини. Вчені дослідили, що проростання викликає хімічна речовина стригалактон.[2] Прикріпляється до хазяїна гаусторієм. Якийсь час рослина залишається під землею, після чого починає швидко рости і відразу вкривається квітами. Запилюється самостійно до розкривання квітів.
Росте у Африці.
Уражує культурні та дикі рослини родини злакових (Poaceae), сорго (Sorgum), плоскуха (Echinochloa), пальчатка (Digitaria). Знижує урожайність на 40 –100% пшениці, овес, жита, сорго, проса, суданської трави, кукурудзи, рису, цукрової тростини.
Striga hermonthica là loài thực vật có hoa thuộc họ Cỏ chổi. Loài này được (Delile) Benth. miêu tả khoa học đầu tiên năm 1836.[1]
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Striga hermonthica là loài thực vật có hoa thuộc họ Cỏ chổi. Loài này được (Delile) Benth. miêu tả khoa học đầu tiên năm 1836.
赫蒙思独脚金（学名：Striga hermonthica）是独脚金属的一种半寄生植物。它对高粱和大米等主要作物具有破坏性[1]。在撒哈拉以南非洲，除高粱和大米外，还会感染玉米，珍珠粟和甘蔗[2]。通过宿主产生的独脚金内酯发芽生长[3]。
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Striga hermonthica
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