Determinants of rice varietal diversity in the region of Vakinankaratra (Madagascar)

Abstract

Déterminants de la diversité variétale du riz dans la région de Vakinankaratra (Madagascar) Résumé Mieux connaître les dynamiques de l'agrobiodiversité est nécessaire pour intégrer sa préservation et sa valorisation dans les stratégies d'augmentation de la productivité agricole. La dynamique de la diversité variétale du riz a été analysée dans la région de Vakinankaratra, Madagascar, en 2006, à travers des enquêtes collectives et individuelles auprès d'un échantillon de 1 050 exploitations réparties dans 32 villages, et par la collecte et la caractérisation des variétés de riz utilisées dans ces villages. La richesse variétale moyenne des villages (10,9) et des exploitations (2,2) est comparable à celle qui est observée dans d'autres agrosystèmes traditionnels, mais on observe une grande variabilité régionale dont les déterminants sont l'altitude, les systèmes agraires, les rizicultures pratiquées et la richesse des exploitations. Il existe une grande disparité dans la fréquence d'utilisation des variétés, un grand nombre de variétés « mineures » étant utilisées par moins de 10 % des exploitations. La gestion des semences se caractérise par l'absence de sélection pour la pureté variétale mais aussi par l'élimination des grains mal remplis. L'adoption de nouvelles pratiques de gestion des variétés et des semences, associée au développement récent de la riziculture pluviale, montre l'ouverture de ces agriculteurs aux innovations. Les perspectives du maintien de la diversité génétique in situ sont discutées.

On-Farm Management of Rice Diversity, Varietal Preference Criteria, and Farmers’ Perceptions of the African (Oryza glaberrima Steud.) Versus Asian Rice (Oryza sativa L.) in the Republic of Benin (West Africa): Implications for Breeding and Conservation

“…The average number of varieties cultivated per village in the study area is low compared to that found in the villages of the island of Madagascar (10.9; Radanielina et al 2013), Guinea (24.6;Barry et al 2008), and in the Kumaun region of Indian Central Himalaya (11; Agnihotri and Palni 2007). However, the diversity maintained at the household level (2.2) is almost similar to that held by Malagasy (Radanielina et al 2013), and Indian farmers (Laishram et al 2020), but lower than those held by Nepalese farmers (Bajracharya et al 2010). The low diversity observed at Igbo-Idé village could be explained by the fact that farmers of this village began to grown rice after recent sensitization campaigns carried out by government extension services and NGOs to promote the crop in the area considering that it is suitable for rice production: therefore, farmers grow only the recent rice varieties with high market value.…”

“…Our results regrouped the rice accessions in 21 morphological groups based on seed characteristics. This diversity is very low compared to those found in Guinea (387 rice varieties; Barry et al 2008), in Bangladesh (670 unique rice varieties; Tiongco and Hossain 2015), and in Madagascar (346 rice varieties; Radanielina et al 2013). However, as in Lao (Appa Rao et al 2002), we noted that the same rice variety could be called by different names and different varieties could have the same name.…”

“…Through the surveyed ethnic groups, 91 names of rice varieties were recorded, indicating the long history of rice production in Benin, but also a quite considerable rice diversity. Similar to the Malagasy (Radanielina et al 2013), Nepalese (Bajracharya et al 2010), andLao (Appa Rao et al 2002) rice producers, most of the names given to rice varieties had significant meanings, and reflected, for the majority, the rice morphological characteristics. Thus, the knowledge of the meanings of the rice names did not only facilitate communication and knowledge exchange between researcher or agricultural extension workers and farmers, but could also help the researcher in the visual identification of some rice varieties based only on their name.…”

Genome Scan of Rice Landrace Populations Collected Across Time Revealed Climate Changes’ Selective Footprints in the Genes Network Regulating Flowering Time

“…Geographic areas where farming systems, not yet affected by the Green Revolution, still rely on a large number of landraces constitute a good setting for such empirical analysis of the genetics of crop species adaptation to climate changes. Indeed, when spread over a broad environmental gradient, those landraces can collectively represent a meta-population harbouring large standing genetic variation (Barry et al 2007c ; Radanielina et al 2013 ), that has evolved historically through processes of human and natural selection (Bellon et al 1997 ).…”

Genome scan of landrace populations of the self-fertilizing crop species rice, collected across time, revealed climate changes’ selective footprints in the genes network regulating flowering time

“…Geographic areas where farming systems, not yet affected by the Green Revolution, still rely on a large number of landraces constitute a good setting for such empirical analysis of the genetics of crop species adaptation to climate changes. Indeed, when spread over a broad environmental gradient, those landraces can collectively represent a meta-population harbouring large standing genetic variation (Barry et al, 2007c; Radanielina et al, 2013).…”