Isolation and characterization of species-specific repetitive DNA sequences of G. longicalyx relative to G. hirsutum

Abstract

The purpose of this work was to isolate and characterize repetitive DNA sequences present in G. sturtianum and G. longicalyx but lacking in G. hirsutum. By using repeated DNA sequences as species-specific molecular and molecular cytogenetic markers, the genetic improvement of the cultivated tetraploid species, G. hirsutum and G. barbadense may be promoted. Furthermore, probes exhibiting species-specificity could provide convenient markers for discriminating among taxonomic groups, and for analyzing phylogeny. Initially, the species-specific nature of G. sturtianum and G. longicalyx repetitive sequence clones were used in hybridizations to Southern blots of G. hirsutum and G. sturtianum or G. longicalyx genomic DNA. Thirteen of 118 G. longicalyx recombinant plasmids and 4 of 80 G. sturtianum were selected based on results of the initial screening. Each of the 4 G. sturtianum and 13 G. loncjicalyx recombinant plasmids selected in the initial screening were further characterized by hybridization to genomic DNAs of 16 species representing 7 genomic groups of the genus Gossypium. Two of the 4 G.turtianum clones examined were specific for G. turtianum, but none of the II 8 G-. clones were confirmed specific by secondary screens. The G-. turtianum recombinant plasmids were further characterized by hybridization togenomic DNAs of three monosomic addition plants, MA Cl-A, MA Cl-C, and MA Cl-D, each of which includes a full complement of G.irsutum chromosomes plus a specific G-. turtianum chromosome. The G.turtianum repetitive DNA clone pCL8 was present in the Cl-C and Cl-D plants. Lanes of both the Cl-C and Cl-D plants showed faint hybridizations relative to the G. turtianum and pentaploid lanes. The G. turtianum repetitive DNA clone pCL21 was present in all three of the monosomic alien addition plants tested.