Analysis of the diversity of onion (Allium cepa L.) cultivars from Niger for their conservation and improvement

Onion is one of the most significant vegetables in Niger because of its use as food and medicine. Three complementary approaches were applied to identify and characterize Niger local onion varieties and ecotypes. These have permitted the classification of the existing local diversity according (i) a nomenclature employed by the farmers, (ii) their morphology based on Biodiversity International scientific descriptors, and (iii) their genotype through the use of microsatellite markers.

Interviews conducted with producers have permitted to inventory fifty two local names. But after analysis and grouping by synonyms, it was found that seventeen ecotypes were produced in Niger. The main criteria for a local ecotype naming are the color of the onion bulb and the production area. The most distinctive quantitative and qualitative variables between ecotypes are leaves length and diameter, bulbs weight, leaves color, bulbs shapes and colors, the uniformity of bulbs shapes and colors. The genetic distance was larger, on one hand, between the most geographically distant ecotypes and, on the other hand, between the most different ecotypes in terms of morphological characters. The number of morphotypes varies from one to nine by tested ecotypes. Molecular analyzes confirm the high variability within ecotypes and conclusions concerning the genetic distance observed from morphological data.