Genetic polymorphism detection in brazilian perennial cottons (Gossypium spp.) using an ISSR marker system and its application for molecular interspecific differentiation

Background: The semi-domesticated Brazilian perennial cotton (Gossypium spp.) germplasm is considered a source of variability for creating modern upland cotton varieties. Here we used Inter-simple Sequence Repeat (ISSR) markers to detect intra and interspecific genetic polymorphism in Gossypium hirsutum L. r. marie-galante and Gossypium barbadense L. and to use molecular data to assessing genetic diversity and molecular discrimination of these species.

Methods and results: The sets contained 12 G. barbadense genotypes and 16 G. hirsutum genotypes from a Brazilian collection. The 11 ISSR primers were used for genotyping yielded 101 bands (polymorphism = 47.5%) and were classified as moderately informative (PIC = 0.304). The ISSR markers exposed a greater diversity in G. hirsutum (P = 24.72%; H_E =0.071 and I = 0.111) as compared to G. barbadense (P = 17.98%, H_E = 0.043 and I = 0.070). The AMOVA analysis showed that 89.47% of the genetic variation was partitioned within species which is supported by Nei's genetic differentiation (G_st = 0.598) and gene flow (N_m = 0.338), suggesting that strong reproductive barriers between species. The UPGMA Cluster Analysis, Principal Coordinate Analysis and Bayesian Model-Based Structural Analysis divided the 28 genotypes into two main clades consistent with the taxonomical delimitation.

Conclusion: The ISSR marker system offers a new approach to determining molecular differences between two cotton species (G. hirsutum L. r. marie-galante and G. barbadense L.). This study can expand the molecular marker resources for the identification and improvement of our knowledge about the genetic diversity and relationships between perennial cotton genotypes.