EST-SSR sequences revealed the relationship of D-genome in diploid and tetraploid Species in Gossypium

Tetraploid cotton species included two subgenomes, named as A-subgenome and D-subgenome, respectively. Prior to this study, the D-subgenome donor in tetraploid cotton species remained elusive. In a previous study, simple sequence repeats developed from expressed sequence tags (EST-SSRs) of G. raimondii was found to possess a high polymorphic frequency between G. hirsutum and G. barbadense [W.Z. Guo, C.P. Cai, C.B. Wang, Z.G. Han, X.L. Song, K. Wang, X.W. Niu, C. Wang, K.Y. Lu, B. Shi,T.Z. Zhang, A microsatellite-based, gene-rich linkage map reveals genome structure, function, and evolution in Gossypium, Genetics 176 (2007) 527-541]. We questioned the role of the D-genome cotton species in the evolution of tetraploid cotton. In this paper, 14 EST-SSR primer pairs from G. raimondii were used to amplify 23 species in Gossypium. In total, 438 amplicons were cloned, sequenced and analyzed. A phylogenetic tree of 13 D-genome diploid species and 8 AD-genome tetraploid species was constructed based on the combined simple sequence repeat (SSR) flanking sequence data. The results showed that 13 D-genome species were congruent with Fryxell's subsection taxonomy. The relationship between D-subgenome tetraploid species and D-genome diploid species indicated that G. raimondii is the sole D-genome donor of all tetraploid species. (c) 2008 Elsevier Ireland Ltd. All rights reserved.