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Since soil pores during waterlogging are filled with water, the diffusion of gases is hampered resulting in anaerobic conditions. Benth., a major biotic constraint to sorghum production in Africa and difficult to control. In the present review, constraints under four categories are briefly discussed. Found inside – Page 428When the host range is carefully examined it is clear that the parasite is not simply attacking the most abundant roots . Yet , this parasite is considered ... On the contrary, due to the presence of four distinct seasons in the temperate, the overwintering of most pests and diseases is halted. It has spread dramatically in the past few decades, now occurring in almost all low and mid-altitude cereal growing regions (Wondimu and Rezene, 1987). A sorghum field severely infested by a striga weed. For example, inoculation with A. lipoferum of mung bean (Vigna radiata) infected with root-knot nematode (Meloidogyne incognita) led to fewer root galls and egg masses per root system. Found inside – Page 98Striga asiatica (L.) Kuntze. Striga asiatica attacks the same crops as S. hermonthica and in particular maize and sorghum. It is distributed predominantly ... Striga infestation is aggravated by low soil fertility and mostly affects resource-poor farmers. Poor in nutrition: Root and tuber crops such as cassava and enset produce high yield, however; the products are largely starchy materials that are deficient in other essential nutrients particularly protein. Found inside – Page 274It may occur together in the same field with other Striga species, ... and severity of attack by S. hermonthica is greater in soils that are sandy, ... The minute seeds of witchweed are produced in large numbers and can remain viable in the soil for many years, particularly under dry conditions. Though limited in their efficiency, the control strategies available today represent major progress toward combating Striga when compared with the absence of any means some years ago. The host range of parasitic plants may also vary substantially, and some species are able to . The most important witchweed species is S. hermonthica, which ranges from Ethiopia and Sudan through Sahel, north into Arabia, and south to the Ivory Coast, Nigeria, Angola, Namibia, and the Lake Victoria basin. Integration of indigenous endophytes in best management practices could improve plant production and health through RIDER mechanisms (Kaushal and Wani, 2016). Access and timely availability to inputs such as improved seeds, fertilizers, pesticides, irrigation, and machineries have substantial effect in promoting productivity. Found inside – Page iThis beautifully illustrated book covers all parasitic families and most of the genera and discusses all main aspects of their biology. As millets are mostly grown in the dryland situations, availability of water is meager and uncertain. (e) Phtheirospermum japonicum (Pj) germinates in the absence of a host. A third option involves catch cropping. Accessibility the majority of records were relevant to this study, because of the high regional importance of this genus and the proven effectiveness of some EWM solutions for its control. 8600 Rockville Pike Bashan and Holguin (1997) argue that interactions between plant genotypes and Azospirillum bacterial strains are complex; and even under stress conditions, some strains can increase plant susceptibility to plant pathogens or even become pathogenic itself. Seeds of host-stimulated hemiparasitic species (Striga, Alectra) have only PD. The slender stems can be unbranched or branched from the middle[855. . Paolo Bàrberi, in Advances in Agronomy, 2019. produce high amount of yield but are associated with a high risk of post-harvest losses due to short shelf-life. Every year, diseases, insect pests and weeds cause substantial yield loss to both major and orphan crops. (2004) mapped five resistance QTL in a recombinant inbred line (RIL) population from N13 (resistant) × E36-1 (susceptible) cross. These are chemicals that stunt the growth of shoots, but stimulate growth of roots, all to the advantage of the parasite. Found insideThis book brings together technologies contributing to the three pillars, explains the context in which they can be scaled up, and identifies research and development gaps as areas requiring further investigation. More interestingly, we are facing an accelerated progress in the genomic and biotechnological research that should soon provide important understanding of some crucial developmental mechanisms in both the parasite and their host plants, thereby enhancing the efficiency of breeding for Striga resistance in millets. ), Striga hermonthica Hemsley and Skan, Striga hermonthica (Del.) Raúl O. Pedraza, ... Beatriz E. Baca, in Beneficial Microbes in Agro-Ecology, 2020. Box 44, Kisumu, Kenya. It has been shown that (i) Striga is able to alter levels of important hormone such as abscisic acid (ABA), cytokinins, and gibberellic acid during infection [12] and (ii) acquire genes from its host and modify them for parasite use [13]. Studies in India showed that the critical stage of weed competition in millets is 4–6 weeks after planting (Mishra, 2015). (2009) who reported that Azospirillum sp. In pot experiment conducted in Nigeria and Kenya, significant plant growth promotion was observed in maize under Striga hermonthica infestation when inoculated with three different endophytes Pseudomonas sp. Both major and orphan crops are low yielders in Africa. . ), Kochia (Kochia scoparia [L.] Schrad. Mishra, in Biotic Stress Resistance in Millets, 2016. Regarding the role that beneficial soil bacteria may play in plant defense against root herbivores, Santos et al. The number of Striga plants per host crop plant ranged from 1.2 to 12.7. Another variety, Striga gesnerioides, attacks cowpeas and other legumes. lycopersici, Rhizoctonia solani, and Pythium sp. It involves establishment of two perennial forage species in a planned design within a maize field, to achieve integrated pest and crop management (Cook et al., 2007). 14.1. In a S. hermonthica-infested clayey soil cropped to maize, AOA abundance was promoted, suggested their ability to adapt to the presence of biotic stressors. Given the complexity of the subject, several search runs were done using various search terms and combinations thereof. 1. The extent and severity of biotic stresses are more pronounced in tropical region than in the temperate region. Lour.) is a major pest of Sorghum bicolor (Linn.) Some herbicides can be applied directly to the emerged witchweed to control them. FOIA Isolates grown on compost were more effective in reducing striga seed germination than those grown on chopped sorghum straw (Yonli et al., 2006). It attaches to the root of the growing plant and sucks water and nutrients out of the host and . tomato, and also when both microorganisms were coinoculated on seed (Bashan and de-Bashan, 2010). Orobanchaceae parasites attack their hosts and how the hosts mount a defense against the threats. Combination between host resistance and biocontrol is thought to be a key EWM strategy for striga in the years to come (Mrema et al., 2017, 2018; Shayanowako et al., 2018). Found insideThis book provides a wide-ranging coverage of the successes and failures of the classical techniques; it describes the advances towards modern technology and addresses the problems of pathogen variation. In contrast, in the case of Striga spp. Find out how the coronavirus can affect the body in mild and severe cases. Kountche, ... B.I.G. Excellent striga control (65–84% reduction) has been observed by using two granular mycoherbicides (Foxy 2 & PSM 197) on both susceptible and resistant maize and sorghum, although effects on yield were limited (Schaub et al., 2006). A pure crystalline germination stimulant of Striga seeds was first isolated in 1966 from cotton root exudates by Cook et al.1007 This stimulant, termed strigol, was determined to be a terpenoid lactone carrying a unique four-ring structure1008 (Figure 40). Striga seeds normally germinate when stimulated by root exudates of Sorghum cultivars and other host plants (Andrews). Some possible mechanisms used by Azospirillum to reduce damage from pathogens have been demonstrated as environmental competition and displacement of pathogens, inhibition of seed germination of parasitic weeds, general enhancement of plants to resist pathogen infection, and possible inhibition of fungal growth via production (at least in vitro) of microbial toxic substances. Millets have an inherent capacity of drought tolerance. Epub 2019 Oct 5. Kishore (1998) also described that inoculation of sorghum plants with A. brasilense produced a decrease in the incidence of sorghum shoot fly Atherigona soccata. Found inside – Page 78Because Striga attacks cereal grains and sugar cane (grasses), ... It is proposed that compounds such as syringic acid (31) from Sorghum bicolor roots are ... Trap crops stimulate seed germination of this weed but are not themselves attacked. Striga species affect the potential productivity of cereals in sub-Saharian Africa due to the lack of durable Striga-resistance in host crops. Please enable it to take advantage of the complete set of features! This makes the bacteria have a competitive advantage with respect to microorganisms that do not produce it, especially fungi, limiting their growth by decreasing the availability of iron in the rhizosphere, while favoring iron nutrition of the plant (Glick, 1995). Of the 30 species, 4 are notable pests. Since AM fungi facilitate the uptake of water and mineral nutrients (such as phosphate and nitrate) by the host plants, it is considered that plants have evolved to produce strigolactones in order to enable AM fungi to colonize their roots.1010,1011,1013 Parasitic plants are thought to abuse these chemical signals to recognize the vicinity of a potential host plant (Figure 41). ), Redroot pigweed (Amaranthus retroflexus L.), Green foxtail (Setaria viridis [L.] Beauv. Found inside – Page 466Three critical factors that limit its yield are lepidopteran stemborers, ... to be directly resistant to Striga attack (Verkleij and Kuiper, 2000). Following this discovery, several strigol-related compounds have been identified as germination stimulants of parasite seeds in root exudates of various plant species. (f) A P. japonicum root grows toward its host's (Arabidopsis) root. (Harish et al., 2008), Burkholderia spp. Benth. Journal of Experimental Botany 46 1817-1823. For these farmers, the feedbacks between poor soils and parasitic plant infestation may eventually cause the farmers to abandon plots of land and move elsewhere. Biological functions of strigolactones. mexicana), a naturally occurring grass related to maize. Images of this innovation are available, see: http://www.scienceinpublic.com.au/wp-content/uploads/magazineSP08Consolata-James-push-pull.jpg, Paolo Bàrberi, in Advances in Agronomy, 2019. The fertility of the land and the land tenure system have huge impact on crop productivity. Drought: moisture scarcity is the most wide-spread challenge to crop production. (2014) reported that colonization of corn (Z. mays) by A. brasilense affects the host selection and performance of the insect Diabrotica speciosa. Azospirillum also has the ability to act against the enemies of plants by indirect mechanisms, by induction of the plant's own defense. Mixed cropping involves planting suitable and unsuitable hosts, and it has been demonstrated to reduce the impact of some witchweeds. As a parasite, Striga is entirely dependent on its host-plants. The effect on AOA was fastened by incorporation in soil of Tithonia diversifolia residues. Four species, namely Striga asiatica (L.) Kuntze (syn. By continuing you agree to the use of cookies. R. Madhusudhana, in Breeding Sorghum for Diverse End Uses, 2019. interactions Between Khinanthus minor and Its Hosts 371 Borg 2005). Found inside – Page iiThis `Technical Manual' provides up-to-date methodologies for various aspects of research and extension related to parasitic weed species of the genera Striga, Alectra, Orobanche and Cuscuta. The land is seeded with susceptible hosts to induce germination of parasitic plants, but the crops are destroyed before the parasite can reproduce. The seeds of grass pea contain a neuron-toxic substance called ODAP [β-N-Oxalyl-L-α, β-diaminopropanoic acid] (Yan et al., 2006). ches" its host before it emerges and becomes visible above ground. This method has the added advantage of helping increase yields, but the benefits of using this method alone over a long period of time have not been demonstrated. Found inside – Page 29It is imperative that all Striga plants be pulled before seed is set ; otherwise , the soil becomes reinfected with seed which will result in attack to ... It is best known for the damage it causes to cowpeas in West Africa, but it also damages tobacco in East Africa. When the seedlings have attached to the root it grows underground for 4-7 weeks before they emerge and are actually seen in the field. Prevention of seed production by Striga by any means has a major effect on the control of this obnoxious weed. Epub 2008 Apr 23. Trap cropping, catch cropping, and crop rotation are other effective ways of managing the land. The common name witchweed synonymous with the Latin name Striga befits the bewitching effects, viz wilting and chlorosis, the parasite inflicts on its hosts long before it emerges and becomes visible above the ground. One of the better understood mechanisms of resistance against Striga by sorghum is low production of compounds by the host root that Striga seeds require as stimulants for germination. After inoculation with A. lipoferum, plants infected with the nematode had significantly greater growth and biomass, probably related to a greater number of functional nodules on roots that had been infected (Khan and Kounsar, 2000). Found insideTo the world you are an abomination; a monster with unholy abilities. It affects both the quantity and quality of the produce. ), Striga hermonthica Hemsley and Skan, Striga hermonthica (Del.) Cultural practices such as stubble cleaning in millets fields after harvest, crop rotation with nonhosts and with catch crops, mixed cropping without host crops, fertilizer management with high doses of nitrogen as top dressing, and use of resistant or tolerant varieties help in reducing Striga infestation. causes severe loss in yield of millets. farmers. The first wave started 1000s (thousands) of years ago and is currently manifest in the very productive set of staple food crops from the Green Revolution. S. lutea Lour. Striga infestation is a consequence of monocropping of cereals, which host the parasite, and declining soil fertility, which weakens the host plant to striga attack. Poor soil fertility: most African soils are inherently low in fertility due to high weathering and leaching; hence, they are deficient in major nutrients such as nitrogen and phosphorus (Okalebo et al., 2006). Reclaiming acid soils is mostly done using large amount of lime or calcium carbonate which are either unaffordable or inaccessible by small-scale farmers. We use cookies to help provide and enhance our service and tailor content and ads. Therefore, efficient weed control at the pre- and early postemergence stages is essential. The roots of potential hosts respond differently when Rhinanthus minor attempts to form haustoria (Cameron 2004). Striga are obligate root-parasitic plants of the major agricultural cereal crops, including millets, in tropical and semi-arid regions of Africa, Middle East, Asia, and Australia. Biotic stresses refer to the type of stresses caused by the living organisms. Epub 2013 Apr 6. However, interactions in the rhizosphere between host roots and Striga seedlings are concealed and inscrutable. This is mainly due to the presence of more conducive environment in the tropics throughout the year where pests and diseases are continuously feed on their host. More important, early hand pulling prevents reseeding. Summary of these constraints is indicated in Fig. Soil salinity: Soil salinity which is characterized by a high concentration of soluble salts, affects crop productivity. Striga is the most economically important member of Scrophulariaceae family of parasitic plants, which attacks cereal crops, particularly sorghum, pearl millet, rice, maize, as well as tobacco and sugarcane in Africa, India, Asia, Australia, and some parts of the USA (Musselman, 1980).
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