The genetic structure of B. cucurbitae was characterized at different spatial scales by considering (a) 25 worldwide-distributed populations (n=570) genotyped at 13 microsatellite loci and several samples genotyped at 2 mitochondrial gene fragments (COI, ND6), (b) 17 populations from East, West and Central Africa genotyped at 19 microsatellite and 3 mitochondrial gene fragments (COI, COII, ND6), (c) 2258 specimens sampled in La Réunion from different wild and cultivated host plants and at three altitudinal ranges and genotyped at 10 microsatellite loci and at 2 mitochondrial gene fragments. Microsatellite show that B. cucurbitae can be subdivided into five main worldwide distributed groups corresponding to populations from (1) the African continent, (2) La Réunion, (3) Central Asia, 4) East Asia and (5) Hawaii. The analysis of inter-regional assignments and the higher values of genetic diversity in populations from Pakistan, India and Bangladesh suggest that B. cucurbitae originated in Central Asia and expanded its range to East Asia and Hawaii on one hand and to Africa and the islands of the Indian Ocean on the other. Levels of genetic structuring within the African continent are much less pronounced. Still we can observe four main population groups colonizing Congo, West Africa, Sudan and East Africa, respectively. The Bayesian assignment of STRUCTURE shows further genetic structuring in East Africa, with populations from Uganda diverging from those of Tanzania and populations from Burundi and Kenya sharing admixture proportions with West African samples. In La Réunion, three distinct genetic clusters of B. cucurbitae are present which are different from the African and Asian groups. Genetically, these 3 clusters are poorly diversified and no recent bottleneck was observed. Results also suggest that these clusters show distinct spatial distributions in the island and that their genetic structure is linked with environmental factors such as altitude or rainfall but