Genetic diversity of the two cultivated rice species (O. sativa & O. glaberrima) in Maritime Guinea. Evidence for interspecific recombination

Abstract

In Maritime Guinea, the interpenetration of upland, lowland and mangrove rice growing ecosystems has found expression in the cohabitation of the two rice cultivated species. Recent changes in cropping practices may lead to the replacement of local varieties by modern high-yielding varieties. In the framework build-up of a strategy for the preservation of local varieties, we analysed the extent, the organisation and the specificities of the rice genetic diversity. One hundred seventy accessions collected in farmers' fields were genotyped with 11 SSR markers and phenotyped with 26 morpho-physiologic descriptors. The general organisation of rice genetic diversity in Maritime Guinea, and its tight relationship with the rice growing ecosystems were similar to the one observed elsewhere. The two major subspecies of O sativa--indica and tropical japonic--as well as the two major ecotypes of O. glaberrima--''floating'' and ''upright''--were present. Moreover, an original genetic compartment was detected, highlighting the occurrence of glaberrima · sativa hybridisation. Allelic diversity was found to be comparable to that noted worldwide for indica and japonica groups of O. sativa, but not as large for O. glaberrima. Given its extent, its original compartment, and its potential for inter-specific and inter-subspecific indica · japonica recombination, the preservation of rice genetic diversity in Maritime Guinea deserves special attention.

Genetic relationships between interspecific lines derived from Oryza glaberrima and Oryza sativa crosses using microsatellites and agro-morphological markers

“…The lack of introgression of the donor parent genome in some lowland NERICA lines could explain some phenotypical differences observed during vegetative and reproductive stages of these lowland NERICAs. Indeed, the genome of the O. glaberrima parent can be partially introgressed on progenies when the crosses are carried out with an O. sativa variety (Barry et al, 2007). Also intensive selection occurred during the selfing of the BC 2, BC 3 and BC 4 generations according to the number of the traits concerned.…”

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“…Asian rice (Oryza sativa L.), comprises two main sub -species which are indica (adapted to floating tropical and subtropical regions or lowland and irrigated agricultural systems) and japonica (adapted to tropical highlands) (Tendro Radanielina et al, 2013). Several collections of these species (Oryza sativa L., and Oryza glaberrima Steud) exist throughout the world (Barry et al, 2007) and mostly at the genebanks of IRD in France, The…”

“…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.…”

Microsatellite marker-based genetic variability in Spanish rice cultivars and landraces

“…Furthermore, landraces are adapted to local agro-environmental conditions which contributes to yield stability and hence, they continue playing an important role in traditional and subsistence farming (Camacho-Villa et al, 2005). However, extensive efforts to improve rice productivity have led to large-scale cultivation of highyielding genetically uniform varieties, the replacement of local cultivars and the concomitant decrease in rice genetic resources that created a widespread concern to promote conservation of traditional cultivars/landraces (Kohli et al, 2004;Camacho-Villa et al, 2005;Barry et al, 2007).…”

“…Microsatellite markers has been used to study interspecific relationships between Oryza sativa and either wild (O. rufipogon and O. nivara) or cultivated (O. glaberrima) species (Ni et al, 2002;Barry et al, 2007). Ni et al (2002) also determined the pattern of diversity in indica and japonica rice subspecies and, within the japonica group, in both temperate japonica and tropical japonica types.…”