INTRODUCTION

Senegal is one of the countries in West Africa with the higher rice production and consumption levels across the African continent along with Nigeria, Guinea, Cote d’Ivoire, Sierra Leone, and Mali. The country is bordered by Guinea-Bissau, Mali, and Mauritania and surrounds its much smaller Anglophone neighbor, Gambia (World bank, 2019). As a Sahelian country, Senegal is associated with semi-arid and high temperatures due to its proximity to the Sahara Desert. Agriculture is the main industry which supports 73.8% of the households but contributes only 7.6% to its GDP (ANDS, 2014;ANDS, 2017). The major staple food crops are rice, millet, corn, and sorghum while industrial cash crops include peanut, cotton, cassava, cowpea and sesame.

Since the 1980s, rice consumption has surpassed the consumption of more traditional crops such as sorghum and millet in Senegal (Colen et al., 2013). To meet the rapid increasing demand, Senegal relies heavily on imported rice. For example, in 2019, Senegal imported 957,222 tons of rice (MAER 2020;ANDS 2020), which represents about 44% of Senegalese rice demand in a year. The rapid increase in rice demand is attributed to changes in consumer preferences and urbanization (AfricaRice, 2011). Migration of rural people to the towns and cities caused changes in diets from those based on other cereals or root crops to rice (Hossain, 2007). The convenience of rice storage, low preparation cost, as well as the ease and short time of cooking rice are among the key attributes spurring rice consumption. Working women have less time for food preparation and have a tendency towards convenience sources of calories (Reardon, 1993). Considering the advantages of rice as the convenient and tasty food, its consumption is projected to continue to rise in the future.

Faced with the shortage of rice supply to meet the local demand and high dependence on imported rice, the Senegalese government has implemented several programs such as GOANA(Grande offensive pour la nourriture et l’abondance) in 2008 and PRACAS (Programme d’acceleration de la cadence de l’agriculture) in 2013 with the ambitious objective of achieving self-sufficiency in rice production (PRACAS, 2013). However, there have been critiques that many large scale irrigation programs have focuses primarily on extension of rice area and failed to improve rice productivity (Diagne et al., 2013). Demont and Rizzoto (2012) recommended upgrading of the rice value chains through investments in post-harvest productquality infrastructure, scaling-up of quality produce by investment in infrastructure, and adoption of sector-wide marketing strategies that enhance the chain competitiveness of domestic relative to imported rice. He also pointed out that increased supply will exist only if there is enough demand to absorb the product and if the product characteristics fit the demand preferences. Creating an environment for improved commercialization of rice will lead to a large demand for rice in urban markets and ensuring the increased development of the rice supply chain in Senegal (Colen et al., 2013). So the main challenges to rice production in Senegal are : 1) how to improve the quality of domestic rice and 2) how to improve production and marketing margins by modernizing production, processing and marketing of domestic rice to satisfy the producers, processors and consumers.

Therefore, both upgrading rice quality as well as enhanced productivity at the same times would be the most important factors to create the virtuous cycle from rice production in rural areas to marketing in the urban areas. However, breeding has been the primary source of technological changes because it provides the most sustainable way to increase rice production and quality via genetic improvement (Fisher, 2015).

Rice breeding in South Korea have made breakthrough in yield potential that occurred from modifying the existing high yield plant types to improve biomass, harvest index, reaching 7~8 tons/ha in polished rice. This is done by formulating prototypes of semi dwarf rice cultivars called ‘Tongil-type’ through wide crosses between indica and japonica cultivars (Osman et al., 2020). With the releases of Tongil-type cultivars, Korea has attained selfsufficiency in rice production to date. Therefore, Tongiltype breeding strategy played a fundamental role to trigger the enhancement of rice productivity in Korea and this could be applied to African situation.

After Korea’s experiences with Tongil-type rice varieties, the Korea Africa Food Agriculture Cooperation Initiative (KAFACI) launched a rice breeding programme to assist 19 African partner countries including Senegal in rice breeding. In this report, we reviewed the rice cultivation and breeding status to get the basic information for implementation of the KAFACI rice breeding project in Senegal.

RICE CULTIVATION AND CONSTRAINTS IN SENEGAL

West Africa has a long history of rice (O.glaberrima) cultivation for 2,000~3,000 years. Still O.glaberrima is being cultivated in Guinea Bissau, Guinea, Sierra Leone and Casamance region of southern Senegal (Olga, 2002). Currently, O. glaberrima is fast being replaced by Asian varieties. In Senegal, high-yielding Sahel rice varieties were first introduced in 1994 and widely adopted by farmers especially in the irrigated regions of the Senegal River Valley. The country produces rice in two different areas: the irrigated Senegal River Valley (SRV) in the northern part, and the rainfed Casamance in southern region (Fig. 1). SRV is the principal rice production region which has around 240,000 ha of the irrigated production systems, enabling double cropping and harvesting twice a year in the region. The SRV has two rice production seasons: the dry hot season (mid Fab/mid~March June/July) and the rainy season (July~November). The dry season has high solar radiation and arid condition which is favorable for rice production. The average rice yields were around 6.4 t/ ha in the dry season, versus 5.5 t/ha in the wet season for the 2003~2010 period (USAID, 2016). Farmers in the SRV have access to tractors and other farm equipment and generally cultivate on a larger area and farm sizes vary between 0.25~2ha (USDA, 2018). The SRV accounted for 44% of the total national rice production areas over the period of 2007~2011, and almost 70% of national rice quantity (SAED, 2013).

The southern, central, eastern regions (Casamance, Fatic and Kaolock) are the rainfed lowland (bas-fond) and upland areas which form the largest rice cultivation areas with more than 400,000 ha in Senegal. Upland and rainfed lowland rice areas grown as a mono-crop. Rice is cultivated on very small farms size with less than 0.1ha with little fertilizer application and without adequate tools and appropriate farm machinery for land preparation, transplanting, harvesting and post-harvest etc. Rice yields are much lower at 1~2 t/ha compared to the SRV, contributing only 30% of national rice production (USDA, 2018).

Around 25~30% of rice produced in the SRV are commercially distributed to other cities, whereas rice that is produced in the Casamance is primarily grown for subsistence purposes and very little rice is distributed to other regions or major cities outside the Casamance (USDA, 2018). Therefore, the SRV region has been the virtual target for attaining the self-sufficiency in rice production as well as raising the competitiveness of domestic rice.

The main constraints to rice cultivation differ from one rice ecologies to the other. In the rainfed ecology, drought, iron toxicity, and pest and diseases constitute the main constraints, whereas salinity, low temperature, bird and pest are the main threats in the irrigated ecology. Atsuko et al (2015) found out that there was substantial yield gap between potential and actual yield obtained by farmers in irrigated rice production in the SRV. The sub-optimal weed and fertilizer management, delayed sowing and late harvesting, bird-control are the major causes of yield gaps. Mean rice yields over nine years were 5.0 and 5.6 t/ha in the Delta and Middle Valley of the SRV, respectively, while mean attainable yields of upper 10 percentile were 7.2 and 8.6 t/ha, respectively. Yield gap between attainable yield and mean yield was 2.2~3 t/ha.

As observed in other African countries, there are enormous potential for increasing productivity in Senegal, considering the vast rice areas and the favorable climate conditions. However, currently there are huge challenges to overcome biological and institutional constraints in Senegal which prevent farmers from intensive rice production include land preparation, labor, seed quality, fertilizer provision, herbicides, credit, varieties, bird control, weed control (Mandiaye et al., 2013).

RICE BREEDING AND PRODUCT PROFILES IN SENEGAL

Agricultural research has a long history in Senegal. Senegal was the headquarters for agricultural research in French West Africa for almost 50 years starting in 1921. From 1921 to 1974, research was in the hands of specialized French inistitutions. In 1974, the national agricultural research institute (ISRA) was created (Tom, 1990). Since then, ISRA have conducted the rice improvement programs through the numerous assistance programs of international organizations. The primary international organizations were IRAT (Institute de Recherche Agronomique Tropicale), CIRAD (Ceneter de cooperation Internationale en Recher- che Agronomicque pour la Developpement), WARDA (West Africa Rice Development Association), IITA (International Institute for Tropical Agriculture) and IRRI (International Rice Research Institute).

The current rice varietal development and release systems are as follows: CGIAR research centers provide the rice germplasm and varieties for use as varietal development in Senegal. Also ISRA has its own rice breeding team creating the basic breeding population for the diverse ecologies of Senegal with the single seed descent (SSD) and the molecular marker-aided selection. ISRA conducts the advanced yield trials (AYT) for two years at ISRA and selects the elite lines. To shorten the varietal development time, the National Performance Test (NPT) is conducted for the elite selections at the farmer’s field at the same time with AYT. At the end of 2 year’s AYT and NPT tests, the best selections are registered as new rice varieties in Senegal and the showcase trial is conducted for 1 year with farmer’s association, seed companies, extension service participated. After new rice varieties are approved for commercialization, ISRA produces foundation seeds and contracts out to farmer unions or other businesses for seed multiplication. After multiplication, first generation (R1) and second generation (R2) seeds are sold as certified seeds. The seed department in the ministry of agriculture certifies seeds after receiving test results from seed treatment centers (STC) in the Senegal River Valley and in the Casamance.

As results, the 60 rice varieties including 9 aromatic and 1 hybrid rice were developed and released since 1994 (Table 1). Among them, AfricaRice contributed to the 22 rice varietal development in Senegal, followed by IRRI (7), IITA(6), and IRAT(1). The foreign national research institutes of Sri Lanka, India, China, Korea, Pakistan, Sierra Leone, Bangladesh, and Brazil also greatly contributed to the development of 17 high-yielding varieties in Senegal while ISRA developed 7 varieties.

Also the 60 varieties were well characterized for specific ecosystem in Senegal: 41 varieties (68.3%) were released for the irrigated ecology, followed by 12 varieties for lowland (20%) and 7 varieties for upland (11.6%) (Table 1 and 2).

The results indicate that rice varietal improvement initiatives in Senegal were more concentrated in the irrigated areas compared to the rainfed ecologies after the release of NERICA varieties. Hence there is need for concerted efforts to increase investments in the rice breeding program for the rainfed areas in the future.

This biased varietal development towards the irrigated areas may be related with the government policy in Senegal. The government’s goal in rice sector has been attaining the self-sufficiency of rice production as well as raising the competitiveness of domestic rice. Therefore, the irrigated ecology in the SRV, which has more favorable conditions to increase rice productivity compared to the lowland or upland in the Casamance region, has been the main focus for investment in releasing high-yielding quality rice varieties. The CGIAR centers and other countries generally have been developing the high-yielding Asian rice varieties mainly for the irrigated ecology in the past green revolution era, and ISRA selected the high-yielding varieties focusing in the irrigated Senegal River Valley. As Maredia et al. (1999) argued, many research and development systems are biased towards crops and varieties demanded by the more commercial or elite farmers. Breeding and varietal release procedures followed by the national agricultural research institutes may not lead to the development and availability of a broad range of varieties to meet the needs of all seed users, especially smallholder subsistence farmers (Tripp, 1994).

It is also noteworthy that the mean paddy rice yield greatly differed in the three different ecologies of irrigated, lowland and upland (Table 3).

The irrigated rice group averaged 7.8 t/ha, out yielding the lowland (5.1 t/ha) and the upland (4.4 t/ha). However, it did not make any significant difference between the two different maturity groups. In the irrigated rice group (Table 2), the early maturing rice varieties with 90~110 days of growth duration, had the mean yield of 7.8 t/ha, which is almost same with 7.9 t/ha in the late maturing group with 110~120 days of growth duration. This was the case in lowland rice with 5.2 t/ha with early maturing group versus 5.1 t/ha with late maturing group.

The early maturity combined with high yielding potential would have been the top priority to rice breeders of Senegal, considering the importance of the double cropping. In Senegal, delayed sowing due to the cold temperature in February and the erratic rainfall in July is the main cause for the failure in the practice of the double cropping system in the SRV, and short-growth duration is the best solution to overcome the delayed sowing in the SRV. Oort (2016) reported that at optimal sowing dates, simulated total long term average potential yields of single, double and triple cropping yields were 10.3, 19.0 and 18.9 t/ha, respectively. With a hypothetical completely cold tolerant variety, yields could increase to 11.2, 20.2 and 20.9, respectively.

As observed across the Africa continent, farmers prefer the early maturing varieties because the earliness of rice can reduce chances for long exposure to the damages from various stresses such as high temperature, drought, flooding, weeds, and salt, and earliness also allows saving the inputs such as labor, water, and cost during rice cultivation period.

However, the early maturing rice generally are less yielding compared to the late maturing rice. Therefore, the rice breeding accomplishments for early maturing rice varieties with high yielding capacity in Senegal (Table 3) are very remarkable. Especially, among 15 varieties (ISRIZ 1~ISRIZ 15) released in 2017, 11 varieties are early maturing varieties with the ranges of 7~9 t/ha of rice yields, which is comparable to the late maturing rice (Table 1). Also the striking breeding advancement was made in the aromatic rice development in 2017. The 7 among 15 varieties were the aromatic rice with early maturity and high yielding (Table 1). Considering the strong demand for the aromatic rice of consumers, locally produced aromatic rice will play quite an important role to increase rice production and raise the competitiveness with the imported rice in the markets. The nine fragrant rice varieties bred are Sahel 177, Sahel 328, Sahel 329, ISRIZ 01, ISRIZ 02, ISRIZ 03, ISRIZ 07, ISRI O8, and ISRIZ 09 are likely to be the entry points for the virtuous cycle in domestic value chains and further replacing imports with domestic rice.

In Senegal, about 45 varieties of rice have been popularized throughout the country from the 1970s to date while in the Senegal River valley, 19 varieties of irrigated rice varieties have been approved since 1994. However, only five varieties are predominantly grown in the farmer’s fields, namely Sahel 108, Sahel 134, and Sahel 177 for the SRV areas among which Sahel 108 is known to occupy around 70% of the SRV. In the rainfed areas, Nerica 4 and DJ 11-509 are leading varieties in the region for the superior traits of earliness, drought tolerance and disease resistances.

Currently, ISRA aims to replace these old varieties with new rice varieties. In the survey for the product profiles of future rice breeding which were conducted during the KAFACI rice breeding workshops by the AfricaRice Sahel regional center in 2018 and 2019, African rice breeders pointed out the necessity of replacing old varieties with the new rice varieties with enhanced grain yield and quality. The rice breeders from Senegal suggested the product profiles with the following traits: high yielding, earliness, high biomass with strong stem, good grain qualities, resistance to various diseases including RYMV and abiotic stresses including cold and salt. So far, more attention has been given to the grain quality for aroma, soft texture in cooked rice, low amylose and high head recovery (Table 4).

However, the implementation plan faced recalcitrance to improve grain quality due to the inherent grain quality of indica germplasm. In general, indica germplasm has higher amylose content between 25~30% and the tendency of easy grain damage from milling due to its long and slender grain dimensions etc. Hence, massive characterization and evaluation for indica germplasm possessing suitable grain quality and yield potential would be basic prerequisite for successful breeding program. Also, another challenge to overcome is that earliness, yield and qualities are negatively correlated with each other and hence it is not easy to combine earliness with high yield and grain quality.

DISCUSSIONS AND CONCLUSION

In Senegal, rice is the main staple food of which annual consumption per capita is around 85 kg. However, Senegal is importing rice to compensate the nation’s rice self-sufficiency gap despite the great potential to increase the rice production. The country has vast irrigated rice areas in the Senegal River Valley where the double cropping is possible and in the rainfed area of in the Casamance region. Rice production in these areas was affected by the several biological and institutional constraints including drought, salt, cold, iron toxicity, and diseases and pest, etc. Despite the capacity challenges in human resources and facilities, Senegal has developed 60 rice varieties including 9 aromatic and 1 hybrid in collaboration with the international cooperation partners such as AfricaRice and IRRI since 1994. Especially, the development of the early-maturing varieties combined with high-yielding varieties were remarkable achievements despite the general observation that the early varieties have less biomass and yield due to the short growth duration.

However, it is noted that genetic improvement to achieve the yield and grain quality at the same times should be done for the development of the next generation of rice in Senegal. To achieve this goal, there is need to develop the intermediate type through the distant crosses between Japonica and African varieties which might be the effective approach to increase the productivity, grain quality and taste at the same time as already verified in the IR8 by IRRI and NERICAS by AfricaRice, and Tongil-type rice in Korea. Historically japonica rice has had a profound impact on rice breeding in Asian countries. IR8, bred by japonica ‘Dee-geo-woo-gen’ and Peta, led to the green revolution in Asia which raised the yield potential of rice from a mere 2~3 t/ha to 8~10 t/ha. NERICA varieties is a good example for improving the rice productivity which have been bred by crosses of Japonica and O. glaberrima in Africa (Saito et al., 2014). In Korea, the so-called ‘Tongil- type’ developed by the same breeding strategy of Indica and Japonica crosses helped Korea achieve and sustain its rice self-sufficiency since 1972 (Kang, 2010). Besides increasing rice productivity, Tongil-type rice could be good resource to improve cold tolerance, grain quality such as grain shape, amylose content, gelatinization, resistance to diseases such as blast and bacterial leaf blight, plant stature, and leaf senescence, among other traits (Kang, 2010). Therefore, Tongil-type breeding tactics which adopts the intraspecific crosses between japonica and indica could provide the innovative and reasonable approach to achieve genetic improvement for yield potential, quality and taste together for the next generation of rice cultivar in Africa.

적 요

세네갈은 농촌진흥청의 아프리카 국제협력사업의 일환으로 수행되는 ^「아프리카 다수성 벼 품종개발 ·보급_」사업의 주 요 회원국으로 본 사업의 효율적 추진을 위해 세네갈의 쌀의 중요성, 쌀 생산 및 육종 현황에 대한 기초정보를 얻고자 조 사하였다.