Background: We investigated root architecture and plant biomass traits of 25 aubergine genepool accessions representative of 9 Solanum L. species, including S. melongena L., grown at two sites in South-East France in order to quantify the diversity of root phenotypes, identify correlations between traits and determine the influence of the environment on trait stability. Method: Aubergine seeds were sown in a mixture of sieved compost and vermiculite in 1m high PVC tubes of 10 cm diameter. Roots and aerial parts were harvested after 4–5 weeks growth. Measured root traits included: root depth and root growth rate, maximum apical diameter, minimum apical diameter, the ratio of daughter to mother root apical diameter, and root inter-lateral distance. Results: • Root maximum diameter and inter-lateral distance showed the largest phenotypic variability between the accessions of S. melongena as well as between the 9 Solanum species. • Most traits were significantly affected by the experimental site except root maximum diameter and shoot dry weight accumulation per day. For most traits there was an interaction between the genotype and the site. • Maximum root diameter and the ratio of daughter to mother root diameter are not correlated with other traits whereas root inter-lateral distance correlates with several traits including root fresh weight. Conclusions: Root architectural traits show diversity within S. melongena and between S. melongena and related species. We confirm that root maximum diameter one of the traits with the highest heritability, i.e., depends on the genotype and is stable in different environments and that root inter-lateral distance is a plastic trait affected by the environment. The study gives some indications on accessions that could be chosen as rootstocks.