Striga hermonthica

Last updated

Purple witchweed
Striga hermonthica.jpg
Striga hermonthica flowers
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Lamiales
Family: Orobanchaceae
Genus: Striga
Species:
S. hermonthica
Binomial name
Striga hermonthica
(Delile) Benth.

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]

Contents

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]

Host and symptoms

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]

Parasitic cycle

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]

Environment

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]

Management

Striga hermonthica growing in maize field in Kenya Striga hermonthica on maize.png
Striga hermonthica growing in maize field in Kenya

Biocontrol

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.

Herbicide priming

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

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]

Impact

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]

Related Research Articles

<span class="mw-page-title-main">Finger millet</span> Species of grass

Finger millet is an annual herbaceous plant widely grown as a cereal crop in the arid and semiarid areas in Africa and Asia. It is a tetraploid and self-pollinating species probably evolved from its wild relative Eleusine africana.

<span class="mw-page-title-main">Pearl millet</span> Species of cultivated grass

Pearl millet is the most widely grown type of millet. It has been grown in Africa and the Indian subcontinent since prehistoric times. The center of diversity, and suggested area of domestication, for the crop is in the Sahel zone of West Africa. Recent archaeobotanical research has confirmed the presence of domesticated pearl millet on the Sahel zone of northern Mali between 2500 and 2000 BC. 2023 was the International Year of Millets, declared by the United Nations General Assembly in 2021.

<span class="mw-page-title-main">Orobanchaceae</span> Family of flowering plants known as broomrapes

Orobanchaceae, the broomrapes, is a family of mostly parasitic plants of the order Lamiales, with about 90 genera and more than 2000 species. Many of these genera were formerly included in the family Scrophulariaceae sensu lato. With its new circumscription, Orobanchaceae forms a distinct, monophyletic family. From a phylogenetic perspective, it is defined as the largest crown clade containing Orobanche major and relatives, but neither Paulownia tomentosa nor Phryma leptostachya nor Mazus japonicus.

<i>Cenchrus purpureus</i> Species of grass

Cenchrus purpureus, synonym Pennisetum purpureum, also known as Napier grass, elephant grass or Uganda grass, is a species of perennial tropical grass native to the African grasslands. It has low water and nutrient requirements, and therefore can make use of otherwise uncultivated lands.

<i>Striga</i> Genus of flowering plants belonging to the broomrape family

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 the Americas. The generic name derives from Latin strī̆ga, "witch".

<span class="mw-page-title-main">Push–pull agricultural pest management</span> Intercropping strategy for controlling agricultural pests

Push–pull technology is an intercropping strategy for controlling agricultural pests by using repellent "push" plants and trap "pull" plants. For example, cereal crops like maize or sorghum are often infested by stem borers. Grasses planted around the perimeter of the crop attract and trap the pests, whereas other plants, like Desmodium, planted between the rows of maize, repel the pests and control the parasitic plant Striga. Push–pull technology was developed at the International Centre of Insect Physiology and Ecology (ICIPE) in Kenya in collaboration with Rothamsted Research, UK. and national partners. This technology has been taught to smallholder farmers through collaborations with universities, NGOs and national research organizations.

<span class="mw-page-title-main">Parasitic plant</span> Type of plant that derives some or all of its nutritional requirements from another living plant

A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the haustorium, which penetrates the host plant, connecting them to the host vasculature – either the xylem, phloem, or both. For example, plants like Striga or Rhinanthus connect only to the xylem, via xylem bridges (xylem-feeding). Alternately, plants like Cuscuta and some members of Orobanche connect to both the xylem and phloem of the host. This provides them with the ability to extract resources from the host. These resources can include water, nitrogen, carbon and/or sugars. Parasitic plants are classified depending on the location where the parasitic plant latches onto the host, the amount of nutrients it requires, and their photosynthetic capability. Some parasitic plants can locate their host plants by detecting volatile chemicals in the air or soil given off by host shoots or roots, respectively. About 4,500 species of parasitic plants in approximately 20 families of flowering plants are known.

<i>Sorghum bicolor</i> Species of plant

Sorghum bicolor, commonly called sorghum and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a grass species cultivated for its grain, which is used for food for humans, animal feed, and ethanol production. Sorghum originated in Africa, and is now cultivated widely in tropical and subtropical regions. Sorghum is the world's fifth-most important cereal crop after rice, wheat, maize, and barley, with 61,000,000 metric tons of annual global production in 2021. S. bicolor is typically an annual, but some cultivars are perennial. It grows in clumps that may reach over 4 metres (13 ft) high. The grain is small, ranging from 2 to 4 millimetres in diameter. Sweet sorghums are sorghum cultivars that are primarily grown for forage, syrup production, and ethanol; they are taller than those grown for grain.

<i>Striga asiatica</i> Species of flowering plant

Striga asiatica, the Asiatic witchweed or the red witchweed, is a hemiparasitic plant in the family Orobanchaceae. It is native to Asia and sub-Saharan Africa, but has been introduced into other parts of the world including Australia and the United States. Asiatic witchweed is a serious agricultural pest, as it parasitises important crop species, including corn, rice, sorghum, and sugar cane, often causing substantial yield reductions.

<span class="mw-page-title-main">Commercial sorghum</span>

Commercial sorghum is the cultivation and commercial exploitation of species of grasses within the genus Sorghum. These plants are used for grain, fibre and fodder. The plants are cultivated in warmer climates worldwide. Commercial Sorghum species are native to tropical and subtropical regions of Africa and Asia.

Sporisorium reilianum Langdon & Full., (1978), previously known as Sphacelotheca reiliana, and Sporisorium reilianum, is a species of biotrophic fungus in the family Ustilaginaceae. It is a plant pathogen that infects maize and sorghum.

<i>Orobanche aegyptiaca</i> Species of flowering plant

Orobanche aegyptiaca, the Egyptian broomrape, is a plant which is an obligate holoparasite from the family Orobanchaceae with a complex lifecycle. This parasite is most common in the Middle East and has a wide host range including many economically important crops.

<span class="mw-page-title-main">Gebisa Ejeta</span> American geneticist

Gebisa Ejeta is an Ethiopian American plant breeder, geneticist and Professor at Purdue University. In 2009, he won the World Food Prize for his major contributions in the production of sorghum.

<i>Orobanche ramosa</i> Species of flowering plant

Orobanche ramosa is a species of broomrape known by the common names hemp broomrape and branched broomrape. It is native to Eurasia and North Africa, but it is known in many other places as an introduced species and sometimes a noxious weed.

Commonly known as Philippine downy mildew, this disease is caused by the species Peronosclerospora philippinensis of the fungal-like protist class Oomycetes, which also has members such as water molds and Phytophthora infestans, which caused the potato blight that led to the Great Irish famine.

<i>Eragrostis pilosa</i> Species of plant

Eragrostis pilosa is a species of grass in the family Poaceae. It is native to Eurasia and Africa. It may or may not be native to North America. It is widely introduced, and it is a common weed in many areas.

<span class="mw-page-title-main">Strigolactone</span> Group of chemical compounds

Strigolactones are a group of chemical compounds produced by roots of plants. Due to their mechanism of action, these molecules have been classified as plant hormones or phytohormones. So far, strigolactones have been identified to be responsible for three different physiological processes: First, they promote the germination of parasitic organisms that grow in the host plant's roots, such as Strigalutea and other plants of the genus Striga. Second, strigolactones are fundamental for the recognition of the plant by symbiotic fungi, especially arbuscular mycorrhizal fungi, because they establish a mutualistic association with these plants, and provide phosphate and other soil nutrients. Third, strigolactones have been identified as branching inhibition hormones in plants; when present, these compounds prevent excess bud growing in stem terminals, stopping the branching mechanism in plants.

<span class="mw-page-title-main">Jonathan Gressel</span>

Jonathan Gressel is an Israeli agricultural scientist and Professor Emeritus at the Weizmann Institute of Science in Rehovot, Israel. Gressel is a "strong proponent of using modern genetic techniques to improve agriculture" especially in third world and developing countries such as Africa. In 2010, Gressel received Israel's highest civilian award, the Israel Prize, for his work in agriculture.

Steven Runo is a Kenyan researcher who is a professor at Kenyatta University. Runo has extensively studied the pathogens of African cereal crops, including Striga. He was awarded the 2020 Royal Society Africa Prize.

<i>Desmodium intortum</i> Species of plant in the genus Desmodium

Desmodium intortum, known as greenleaf desmodium and also as beggarlice along with other members of its genus, is a species of flowering plant in the genus Desmodium, native to Mexico, Central America, northern South America, the Galápagos, Haiti and Jamaica. A nitrogen-fixing fodder crop, it has been introduced to the rest of the world's tropics, including Africa, India, Australia, New Guinea and Taiwan

References

  1. 1 2 USDA, NRCS (n.d.). "Striga hermonthica". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 4 December 2015.
  2. 1 2 Yoshida, Satoko; Maruyama, Shinichiro; Nozaki, Hisayoshi; Shirasu, Ken (28 May 2010). "Horizontal Gene Transfer by the Parasitic Plant Stiga hermonthica". Science. 328 (5982): 1128. doi:10.1126/science.1187145. PMID   20508124. S2CID   39376164.
  3. 1 2 Abbasher, A. A.; Hess, D. E.; Sauerborn, J. (1998). "Fungal pathogens for biological control of Striga hermonthica on sorghum and pearl millet in West Africa". African Crop Science Journal. 6 (2): 179–188. doi:10.4314/acsj.v6i2.27814.
  4. ↑ Johnson, Annie. New South Wales. Witchweed. 2005. http://www.wyong.nsw.gov.au/environment/Weeds_category_one_Witchweed.pdf
  5. ↑ Sand, Paul, Robert Eplee, and Randy Westbrooks.Witchweed Research and Control in the United States. Champaign, IL: Weed Science Society of America, 1990.
  6. 1 2 Agrios, George N. Plant Pathology. 5th ed. London: Elsevier Academic Press, 2005
  7. 1 2 Matusova, Radoslava; Rani, Kumkum; Verstappen, Francel W.A.; Franssen, Maurice C.R.; Beale, Michael H.; Bouwmeester, Harro J. (2005). "The Strigolactone Germination Stimulants of the Plant-Parasitic Striga and Orobanche spp. Are Derived from the Carotenoid Pathway".
  8. ↑ Lane, J.A., Moore, T.H.M. and Child, D.V. 1996. Characterisation of virulence and geographic distribution of Striga gesnerioides on cowpea in West Africa. Plant Disease 80: 299-301
  9. ↑ Gbehounou, G., A. H. Pieterse, and JAC Verkleij. "Longevity of Striga Seeds Reconsidered: Results of a Field Study on Purple Witchweed (Striga Hermonthica) in Benin." Weed Science 51.6 (2003): 940-6. ProQuest. Web. 11 Nov. 2014.
  10. ↑ Abbasher, A. A.; Hess, D. E.; Sauerborn, J. (1998). "Fungal pathogens for biological control of Striga hermonthica on sorghum and pearl millet in West Africa". African Crop Science Journal 6 (2): 179–188.
  11. ↑ Pilgeram, Alice L.; Sands, David C. (2010-08-12), "Bioherbicides", Industrial Applications, Springer Berlin Heidelberg, pp. 395–405, doi:10.1007/978-3-642-11458-8_19, ISBN   9783642114571
  12. ↑ Sands, David C; Pilgeram, Alice L (May 2009). "Methods for selecting hypervirulent biocontrol agents of weeds: why and how". Pest Management Science. 65 (5): 581–587. doi:10.1002/ps.1739. PMID   19288472.
  13. ↑ Nzioki, Henry S.; Oyosi, Florence; Morris, Cindy E.; Kaya, Eylul; Pilgeram, Alice L.; Baker, Claire S.; Sands, David C. (2016-08-08). "Striga Biocontrol on a Toothpick: A Readily Deployable and Inexpensive Method for Smallholder Farmers". Frontiers in Plant Science. 7: 1121. doi: 10.3389/fpls.2016.01121 . ISSN   1664-462X. PMC   4976096 . PMID   27551284.
  14. ↑ "toothpickproject". toothpickproject. Retrieved 2019-05-25.
  15. ↑ Dembélé, B., Dembélé, D., & Westwood, J. (n.d.). Herbicide Seed Treatments for Control of Purple Witchweed (Striga hermonthica) in Sorghum and Millet. Weed Technology, 629-635.
  16. ↑ Igbinnosa, I., and P. A. Thalouarn. "Nitrogen Assimilation Enzyme Activities in Witchweed (Striga) in Hosts Presence and Absence." Weed Science 44.2 (1996): 224-32. ProQuest. Web. 11 Nov. 2014.
  17. ↑ Umar Shahul Hameed, Imran Haider, Muhammad Jamil, Boubacar A Kountche, Xianrong Guo, Randa A Zarban, Dongjin Kim, Salim Al‐Babili, and Stefan T Arold. "Structural basis for specific inhibition of the highly sensitive ShHTL7 receptor" EMBO Reports (2018) e45619. DOI 10.15252/embr.201745619 http://embor.embopress.org/content/early/2018/07/18/embr.201745619
  18. ↑ Khan, Z. R., C. A. O. Midega, D. M. Amudavi, A. Hassanali, and J. A. Pickett. 2008. On-farm evaluation of the ‘push–pull’ technology for the control of stemborers and striga weed on maize in western Kenya. Field Crops Research 106:224–233
  19. ↑ Khan, Z., C. A. O. Midega, A. Hooper, and J. Pickett. 2016. Push-Pull: Chemical Ecology-Based Integrated Pest Management Technology. J Chem Ecol 42:689–697.
  20. ↑ Zwanenburg, Binne; Mwakaboko, Alinanuswe S.; Kannan, Chinnaswamy (November 2016). "Suicidal germination for parasitic weed control". Pest Management Science. 72 (11): 2016–2025. doi:10.1002/ps.4222. ISSN   1526-4998. PMID   26733056.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.