Agro biodiversity and developing a architectural model of the date palm (Phoenix dactylifera L.) in the Sahel : case of the southeast of Niger ; Agro biodiversité et élaboration d'un modèle architectural du palmier dattier au Sahel : cas du Niger

The Sahel is an arid area threatened by climate change that causes great social and environmental vulnerability. Agriculture in Sahel is facing this change to ensure food security for growing populations. The use of plant species with phenological plasticity such as the date palm (Phoenix dactylifera L.), is one of the responses to hard soil and climate conditions to which few plants are adapted. The objective of this thesis is to improve our knowledge on cultural practices, local knowledge around the date palm and genetic and morphological diversity of this species in order to promote sustainable development of oasis agriculture in the Sahel. Thus, we conducted a socioeconomic survey of 30 date palm farmers in 14 villages in Southeastern Niger. Alongside this survey, we collected 113 samples of young leaflets taken from 31 males and 82 females in 19 date palm oasis basins. Our study identified 19 date palm population varieties distinguished on the basis of the fruit color. Date palm has a special double flowering associated with two fruit production seasons in the Sahel. The February-July period is the most productive but early rains limit fruit quality. The evaluation of local knowledge associated with date palm has shown that even if cultural practices are less developed than in the North of the country or in the Maghreb, the profits from the date cultivation significantly contribute to household survival. Furthermore, genetic analysis of date palms in Southeast of Niger has shown that they are a unique group with high genetic diversity. In addition, this germplasm belongs to the Western gene pool and is one of the least introgressed by oriental genetic contributions. The overall genetic analysis revealed a new group in Southern Niger different from that of North Africa and raises the question of its origin. Finally, we have demonstrated the existence of discriminating architectural features in Sahelian date palms. We have developed an architectural model for the calculation of the light interception and ...