Agrobiodiversité du palmier dattier (Phoenix dactylifera L.) au Tchad

Abstract

The cultivation of date palms (Phoenix dactylifera L., Arecaceae), crucial in arid and semi-arid regions, has been declining in Chad since the 1960s due to diseases, pests, and inefficient agricultural practices, exacerbated by environmental and socio-economic factors. The aim of this study is to enhance understanding of date palm agrobiodiversity for sustainable oasis management in Chad. A survey of 60 producers was conducted to gather information on cultivars, associated crops, and cultivation practices. Genetic analysis of 142 cultivars using 18 microsatellite markers allowed for molecular characterization of genetic diversity, including the identification of western and eastern chlorotypes using the chloroplastic marker CpfM12. The study highlights the varietal diversity of date palms in the Sahara, with over 200 cultivars identified through empirical selection. These cultivars, propagated by offshoots, exhibit a single production period from June to September, with an average productivity of 68±19 kg per plant and an average price of 506 FCFA/kg. Farmers have a good understanding of cultivation practices in this region. In the Sahel, three groups of date palm cultivars are mastered by all farmers, distinguished by fruit color (red, yellow, and green) and typically propagated by seeds. In 20 % of date palms, climatic conditions allow for two production periods, in April-May and from June to September. The revenue from selling dates during the second production period exceeds that of the first. Furthermore, molecular variance analysis (AMOVA) revealed a high intra-population genetic variability (polymorphism) of 7 %, although no inter-population structuring was observed across the 18 SSR markers. The genetic diversity of the chloroplastic minisatellite, based on the geographical origin of genetic pools in Chad, indicated an introgression of two chlorotypes (Eastern and Western) in the Saharan zone, with Ennedi-West being 75.5 % Western and Borkou being 78.5 % Eastern. In the Sahelian zone, there is an observed heterogeneity of chlorotypes, with 56 % Western and 44 % Eastern. Enhancing and strengthening date palm agrobiodiversity and expanding palm groves could increase production and income, contributing to food security and the livelihoods of populations in Chad and more broadly in the Sahel region.