Résumé
Moco cotton (Gossypium hirsutum L. race marie-galante (Watt) Hutch.) is a potential source of valuable alleles for breeding programs, mainly because of its great adaptability to semi-arid conditions. With the aim of quantifying moco cotton genetic variability, 187 plants collected in the northeast of Brazil were evaluated using 12 microsatellite markers. A total of 62 alleles were amplified, ranging from three to eight polymorphic alleles per locus. Total genetic diversity was high (0.52), and when measured on a per state basis, was of 0.37 on average. The population showed a low level of heterozygozity (H-O = 0.16), reflecting a high level of endogamy (F-IS = 0.67). Phylogenetic analysis using the neighbor-joining method revealed that plants sampled in different states tended to cluster according to their geographic origin, except for those collected in the states of Paraiba and Rio Grande do Norte, which grouped together. Plants from the state of Piaui formed two groups, one with an apparent allelic contribution from G. barbadense, while the second group of plants was closer to those from the states of Paraiba and Rio Grande do Norte. Despite the high genetic diversity that was observed in the remaining populations, urgent conservation efforts should be undertaken, owing to the high level of endogamy and accelerated extinction process that characterizes these populations. Such efforts should focus on the collection and ex situ maintenance of representative genetic diversity.