Evidence for the Emergence of New Rice Types of Interspecific Hybrid Origin in West African Farmers' Fields

Abstract

In West Africa two rice species (Oryza glaberrima Steud. and Oryza sativa L.) co-exist. Although originally it was thought that interspecific hybridization is impossible without biotechnological methods, progenies of hybridization appear to occur in farmer fields.AFLP analysis was used to assess genetic diversity in West Africa (including the countries The Gambia, Senegal, Guinea Bissau, Guinea Conakry, Sierra Leone, Ghana and Togo) using 315 rice samples morphologically classified prior to analysis. We show evidence for farmer interspecific hybrids of African and Asian rice, resulting in a group of novel genotypes, and identify possible mechanisms for in-field hybridization. Spontaneous back-crossing events play a crucial role, resulting in different groups of genetic diversity in different regions developed by natural and cultural selection, often under adverse conditions. These new groups of genotypes may have potential relevance for exploitation by plant breeders. Future advances in crop development could be achieved through co-operation between scientists and marginalized farmer groups in order to address challenges of rapid adaptation in a world of increasing socio-political and climatic uncertainty.

Tracing ancestor rice of Suriname Maroons back to its African origin

“…), domesticated in western sub-Saharan Africa 3,500 years ago 11 independently from Asian rice (O. sativa L.), which was domesticated in China ∼9,000 years ago 12 . The introduction of Asian rice to Africa pre-dates the period of slavery 13 and both species are grown by African farmers 14 . Under wet conditions, African rice generally gives lower yields than Asian rice, but it is better adapted to low-input agriculture, drought, poor and acid soils, pests and weeds 15 .…”

“…Small-scale farmers across West Africa grow a wide variety of O. glaberrima and O. sativa landraces, and hybrids between the two species that are either selected by farmers or developed artificially to combine the high yield of Asian rice with the hardiness of African rice 14 . Unlike the Maroon rice, African landraces of both species are well represented in germplasm institutes.…”

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“…A total of 136 accessions (Table 1) including 95 accessions collected from different villages and regions of Benin (Odjo et al, 2017a), 32 'unique' off-types and nine check varieties obtained from AfricaRice genebank in Cotonou were considered. The check varieties included three lowland indica (IR841, Adny11, WAB 32), one upland japonica (Gambiaka Kokou), one African rice (CG14) and four Asian-African interspecific hybrids (Nerica-L-20 Nerica-L-19, Nerica 4 and Nerica 2) ( Table 1).…”

“…Contrarily to Guinea, Mali, Nigeria and Niger, that have their rice varieties well collected, studied and stored in different gene banks (Nuijten et al, 2009;Sow et al, 2013) collection from Benin is poorly represented. However, the country has a potential of 205 000 ha of lowlands, plus more than 110 000 ha of irrigable lands (MAEP, 2011) among which barely 10% is currently being used for rice production (MAEP, 2011).…”

“…Local varieties are valuable as they possess a huge treasure of genetic material for development and improvement programs. Several researchers reported the use of agromorphological markers in the characterization and study of rice (Oryza sativa L.) germplasm diversity in China (Yawen et al, 2003), India (Roy et al, 2013), Vietnam (Nguyen et al, 2009), Nepal (Mahendra et al, 2013) and even in Africa (Semon et al, 2005;Barry et al, 2007;Nuijten et al, 2009;Sow et al, 2013). In Benin and in our knowledge, no genetic diversity study on rice is reported.…”