Ecology, Morphology, Distribution, and Use of Sesbania tchadica ( Sesbania Sesban ) from the Republic of Chad: A Review.

: This study on the leguminous plant Sesbania tchadica has made it possible to highlight its description, specification and identification in N'Djamena region S. tchadica ( Sesbania Sesban Merr. (L)) is an annual tree that measures more than 4 meters in height. This species is abundant especially in Ndjamena. In most of the district of Ndjamena, S. tchadica was the most common type. S. tchadica shows a rapid early growth and grows well in various soils especially sandy siltstone and silty shale. The local inhabitants use the species in many ways: as a medicine, a livestock feed, for improving soil fertility, for fuelwood and to repel desert encroachment. In this study, various academic publishing websites like Science Direct, Springer Nature, some online international plant databases, and other national data herbaria from the republic of Chad were used to identify, describe and summarize the research literature on Sesbania Sesban . This paper also describes the morphological characteristics observed in Sesbania Sesban from the republic of Chad and its taxonomy to assist in future program evaluations.


Introduction 25
The taxonomic diversity of legumes is enormous. In addition, they provide important benefits to humans including food, 26 medicines, and environmental services. For example, leguminous food grains include beans (Phaseolus vulgaris L.), peas (Pisum 27 sativum L.), soya beans (Glycine max L.), and forage legumes such as clover (Trifolium repens L.), sainfoin (Onobrychis Mill.) 28 and Sesbania sesban. Other legumes are ornamental, (Cercis siliquastrum, Acacia mollissima) melliferous (Robinia pseudoacacia, 29 Melilotus albus), or medicinal (Ceratonia siliqua, Trigonella foenum-graecum, Sesbania sesban). These plants (leguminosae) also 30 fix atmospheric nitrogen via their symbiotic association with soil bacteria, belonging to the genera Rhizobium, Azorhizobium, 31 Bradyrhizobium, Synorhizobium (Lahdachi et al., 2015). They can be used for soil improvement. They are among the world's most 32 important crops (Toomsan et al., 2012) (Rochester et al., 2001). They provide nutritious bodybuilding food for man and animals 33 the world over (Li et al., 2017). In addition to being rich in protein, leguminous crops are also high in bone-building fibers, complex carbohydrates, minerals, and vitamins essential to good health (Polak et al., 2015) (Maria et al., 2021. They can obtain 35 most of the nitrogen they need from the vast supply of gaseous nitrogen in the air (Cocking, 2000). Air is about 78 percent 36 nitrogen; there are around 6 400 kilograms of nitrogen above every hectare of land and water (NifTAL, 1985). These plants gather 37 and use this nitrogen by working symbiotically with special bacteria (rhizobia) in nodules on their roots (Ndoye & Dreyfus, 1988) 38 (Sharma et al., 2005). Rhizobia infect the root hairs of the leguminous host; nodules develop and become small nitrogen factories 39 on the legume roots. The host plant provides a home for the bacteria and energy to fix or gather air nitrogen. In return, the plant 40 receives fixed nitrogen from the nodule and produces food and forage protein (NifTAL, 1985) (Mmoudiongh. & Rinaudoe, 1985) 41 (Abdel Magid et al., 1988) (Semba et al., 2021). They also leave fixed nitrogen in the soil for succeeding crops (Dakora F. D. and 1994) (Kwesiga et al., 1999) (Orwa et al., 2009) (Sileshi et al., 2014).

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In general, leguminous species from arid habitats play a great role in reforestation development programs and in the fight against 49 desertification (Curasson, 1956) (Bashan et al., 2012. They are suitable alone or mixed with other species for use in arid zone 50 agriculture (Bradbury, 1990). Moreover, the integration of legume trees increases yield stability in cropping systems and prevents 51 land degradation (Sileshi et al., 2008) (Sileshi al., 2012). These characteristics give these « fertilizer trees » a very important 52 economic and environmental value (Kiptot et al., 2014).

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The genus Sesbania sp. includes many species indigenous to Africa such as S. goetzei, S. keniensis S. rostrata and S. sesban, which 54 possess several desirable characteristics that make them suitable for use as multipurpose trees in farming systems, particularly S. 55 sesban (Heering, 1995). Endemic Sesbania sp found in Chad are Sesbania tchadica (Sesbania sesban), Sesbania dalzielii, S. 56 rostrata and others (Jean and Cyrille, 2019).

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One of the most serious constraints to the sustainability of agriculture in sub-Saharan Africa is soil nutrient depletion (Bindraban et 58 al., 2012). Many factors cause the decline of soil fertility and carbon stocks of African drylands including deforestation, 59 overgrazing, unsustainable agriculture, and climate change (DeRouw, 1998) (Bakhoum et al., 2018. One of the solutions is the use 60 of mineral fertilizer; however, they are expensive and unsustainable. To address these challenges, scientists have experimented on 61 low cost agroforestry options for soil fertility replenishment (Bindraban et al., 2012). Planting nitrogen fixing trees such as S. 62 sesban (S. tchadica) is an effective solution for increasing soil productivity (Bakhoum et al., 2018). The International Center for 63 Agroforestry Research (ICRAF) is interested in the role of Sesbania sesban in improved fallows especially in savannah woodland 64 region (Anon, 1992) (Ndungu and Boland, 1994) (Kwesiga et al., 1999). Improved fallows involve planting mainly legume 65 tree/shrub species in rotation with cultivated crops. In Zambia, ICRAF researchers found that growing Sesbania in depleted 66 agricultural fields or on fallow lands for 2 or 3 years and then introducing a hybrid maize crop after the fallow period produced 67 exciting and encouraging results. Without N fertilizers, maize yields were 2.3 t ha-1 after 1 year of Sesbania fallow; 5.6 t ha-1, 68 after 2 years; and 6.0 t ha-1, after 3 years. Continuous maize crops gave only 1.5 t ha-1 (Anonymous, 1985). Shrubs (mostly 69 legumes) and annual crops may be grown together and the shrubs retained as fallows for 2-3 years to improve the soil (Dagar and 70 Tewari, 2017). Afterwards, crops are grown (Kwesiga et al., 1999). Intercropping sweetpotato with other leguminous plants such 71 as Sesbania sesban improves yield of the crop (Muimba-Kankolongo, 2018). Sesbania tchadica (Sesbania Sesban) has many other 72 uses in domestic, environmental, fiber, food, beverages, forage, medicine and wood products and services (Richard and ILDIS, 73 2018). The objective of this paper is to give a general morphological identification and description of Sesbania tchadica A. Chev.

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Page 3 of 25 from the republic of Chad. This paper provides also an overview and updated information concerning this very useful but less-75 exploited plant with the purpose to help develop and conserve it.

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Study area: N'Djamena is the administrative capital and the largest city of Chad Republic. It is located in the center-west of the 78 country (Figure 1), at the confluence of the Chari and Logone rivers. Its population is estimated in 2020 at 1,422,547 habitants with 79 a total growth rate of the country about 3.69% (UN, 2021). N'Djamena has a tropical, arid climate, including a long dry season (7 80 to 8 months, November to May) and a short wet season (3 to 5 months, May to October). Rainfall varies between 400 to 700 81 mm/year with many heavy showers. In recent years, rain falls mainly over a three-month period (July-September). Temperatures       (Gillett, 1963). However, the names "Sesbania" (Auguste, 1913), "Seseban" and "Sesban" already existed (Gillett, 102 1963). Related names or synonyms are Sesbania Sesban var. nubica, Sesbania sesban Merr. (L) (Ndungu and Boland, 1994) 103 (Baker, 1926) or Sesbania aegyptiaca auct. non Pers. (Jean and Cyrille, 2019 . It grows in a wide variety of soils from loose sandy soils to heavy clays (Heuzé et al., 2016). In Chad, especially in 119 N"Djamena, Sesbania tchadica (Sesbania Sesban) often occurred in different types of soil: silt siltstone, limestone, silty shale, 120 sandy soils, and clays ( Figure 3B).

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Biophysical limits: The mean annual growing temperature of Sesbania sesban is between 18 °C and 23 °C (maximum 45 °C) and 122 the mean annual rainfall is from 500 to 2000 mm. The mean altitude is between 100 and 2300m. Sesbania tchadica grows at 123 altitude around 300m (Orwa et al., 2009).

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Sesbania is infected by mild and severe mosaic disease virus, which is transmitted from sap and root, showing vein clearing and 128 reduction of leaflets. The prevalence of infection of mosaic disease virus ranges from 5-20%. Sesbania plants grown ""in vitro"" 129 with mild mosaic virus inoculation had fewer pods and were very small in size. The virus inoculated ""in vitro"" has a great 130 tolerance of dilution (between 1,000-10,000), a resistance to heat (40-60°C) and has long longevity in vitro varying between 10-14 131 days and (10-25°C) (Mall and Kisan, 2003). 136 (Heering, 1995). In Chad, the genus Sesbania sp is represented by many species: Sesbania tchadica A. Chev.  , 1971). Our study shows that the species S. tchadica is abundant in the area that the study was 142 conducted. In the most districts of N"Djamena, we found S. tchadica to be the most common type ( Figure 3A). It shows a rapid 143 early growth and grows well in different soil types in Chad ( Figure 3B). As reported by Jean and Cyrille (2019) (Gillett, 1963) (Ndungu and Boland, 1994) (Jean and Cyrille, 2019). Soaking the 160 seeds in water for a few days is sometimes required to make them germinate (Gillett, 1963). Mani et al., (2011)

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Five varieties of S. sesban are recognized botanically but their differences do not correlate strongly with their agricultural value 165 (Mani et al., 2011). For this purpose, we employ survey data collected from Ndjamena to describe the species Sesbania tchadica 166 (Sesbania Sesban) ( Figure 5 and Figure 6).   Table 2. Sesbania sesban is used as a green manure which increases the nitrogen on the soil (in crops of rice and wheat)

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Tree, roots (Patra et al., 2006) Rhizobuim strains induce root nodules and fix nitrogen from the air on the soil in symbiosis with Sesbania sp.  (Gillett, 1963) The biomass of Sesbania sesban can produce wood within just 3-6 months when it grows with Cajanus cajan (leguminous) and used so as cooking fuel

Whole tree (Adelanwa & Tijani, 2016)
Sesbania sesban is used in many African countries as a good source of fuel, grows fast, burns well, can be coppiced. It is used as fiber for ropes and fishing nets, and the seeds produce a gum. compounds that are, once extracted, very useful for treating diseases, manufacturing of drugs, organic or chemical supplements and 201 antibacterial or antioxidant agents, manufacturing of biological manure, among others (Patra et al., 2006) ; (Kathiresh et al., 2012) (table 202 1). Details of phytochemicals compound combined with different extraction solvents are shown in Table 3. Aqueous extracts (Khare, 2007) Triterpenoids, carbohydrates, vitamins, amino acids, proteins, tannins, saponin glycosides steroids (Leaves, seed)

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Sesbania tchadica is a leguminous tree native to Chad that is used to increase crop yields and vegetation in some desert areas. The local 208 population and particularly pastoralists plant it in arid zones to increase the plant cover, to obtain shade for humans and their animals and 209 to use its wood for construction. The local population also uses Sesbania tchadica to enrich soil fertility for increasing yields of crops 210 such as rice, maize and sorghum and to repel desert encroachment in zones with little vegetation (Ousman et al., 2017) (unpublished). 211 The author (Bashan et al., 2012) have demonstrated that native leguminous trees such as Sesbania tchadica are essential to ensure the 212 revegetation of eroded desert lands and to restore eroded soil. These authors have also inoculated these leguminous trees with Plant 213 Growth-Promoting Bacteria (PGPB) in agricultural and agroforestry systems. They planted a high density of these leguminous trees in 214 certain areas with severely eroded soil and the result was a remarkable degree of revegetation and more stabilized soils. Sesbania tchadica 215 can play an important role, along with other leguminous species, in land restoration and the protection and conservation of indigenous 216 species in Chad (FAO, 2012).

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In the present study, the authors found that most populations of Sesbania tchadica in N"Djamena are planted by the local population 218 whereas in areas surrounding the city, most are wild (Jean and Cyrille, 2019). This suggests that the local population is aware of the 219 importance of the species and wishes to benefit from its fast growth and its use for fuelwood, for improving soil fertility and for feeding 220 and shading livestock. it measures approximately 4-5 meters in height.in six months with a diameter of up to 12 cm (Shun-ching, 1960), 221 (Anonymous, 1985), (Ousman et al., 2017) (unpublished). The average diameter growth measured in basal circumference is ranging from 222 16-28cm (Shun-ching, 1960). In South of Morocco, to support the agriculture systems limited by the lack of water resources and 223 disturbing salinization of surface or underground freshwater sources, the National Institute of Agronomic Research Institut National de la 224 Recherche Agronomique INRA has become interested in the adaptation of certain crops to saline environments and their contribution to 225 improving food and fodder production in desert or arid areas. Successful results of resilient cultures and cover vegetation are obtained by 226 the introduction of Sesbania sesban in a saline environment in the region of Laâyoune (INRA, 2019). Bala et al., (1990) found also that 227 biological nitrogen fixation can be significantly increased by inoculating tree legumes such Sesbania sesban with salinity-tolerant 228 rhizobia under saline conditions.

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However, some important problems exist which threaten Sesbania tchadica and other leguminous trees in Chad. Robert & Mahamat Ali, 230 (2005) pointed out that around cities such as Ndjamena; the high demand for fuelwood threatens the sustainability of supply. Nwilo et al., 231 (2020)

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In the current study, the species Sesbania tchadica was collected using standard procedures by Chadian expert foresters and botanists 242 from the Toumaï Institute and LRID Herbaria. Next, to identify the plant material, the authors used the empirical keys determination 243

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The ethnobotanical study carried out specifically from Ndjamena region and its surroundings allowed the authors to assess at the 252 local level an important tree and shrub species, Sesbania tchadica (Sesbania Sesban). Sesbania tchadica leaves were harvested and 253 organized according to a morphological model in order to facilitate its identification. However, this morphological and descriptive study 254 conducted on Sesbania tchadica proved to be very complex because the exploitation of data at local level still less-exploited. As a result, 255 this paper contributes to the production and maintenance of a new database on this species. It is also a gain for the scientific world and 256 the research organizations in Chad and internationally. This study will hopefully contribute to the protection, use and value of Sesbania 257 tchadica.

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Cheikh Anta Diop University of Dakar, Senegal, Faculty of Sciences and Techniques/Department of Plant Biology) for his reviewing 263 and assessment of this paper. Our gratitude thanks go also to all those who accompanied us during the field work in N"Djamena and its 264 surroundings.

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Ethics approval and consent to participate: The manuscript is not submitted to other journal for simultaneous consideration. The work is original and 267 has not been published elsewhere in any form or language. Authors adhere to discipline-specific rules for acquiring, selecting and processing data

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Compliance with ethical standards 269 Competing interests: The authors have no relevant financial or non-financial interests to disclose.

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Funding: The authors did not receive support from any organization for the submitted work.

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Availability of data and materials: The data that support the findings of this study are available from the corresponding author upon 272 reasonable request. All data relating to this species generated during the study survey are included in this paper. A voucher specimen