Abstract

Random Amplified Polymorphic DNAs (RAPDs) is a DNA polymorphism assay based on the amplification of random DNA segments with single primers of arbitrary nucleotide sequence. Despite the fact that the RAPD technique has become a very powerful tool and has found use in numerous applications, yet, the nature of molecular variation(s) uncovered by the RAPD technique is still unclear. The aim of the following study, therefore, was to investigate the molecular nature of RAPD DNA fragments in fourGossypium barbadense cultivars. Five RAPD DNA fragments, generated by improved RAPD-PCR technique, and representing polymorphic and nonpolymorphic bands were analyzed at the molecular level using DNA sequence analysis. Nonpolymorphic RAPD DNA fragments showed homologies to previously characterized plant structural genes.Comparative nucleotide sequence analysis of two comigrating nonpolymorphic fragments revealed that these two DNA sequences are highly similar to each other, indicating that similarity of fragment size is a good predicator of homology. Polymorphic RAPD DNA fragments, on the other hand, showed homologies to middle and high-repetitive DNA sequences. These results promote the initiative to integrate these RAPD markers in cotton breeding applications, and DNA fingerprinting.

Key words: Gossypium, MITEs, RAPD-PCR, repetitive DNA, sequence similarity, retrotransposons.