Optimization and application of RAPD (Random Amplified Polymorphic DNA) in a recurrent selection programme of cotton (Gossypium spp.)

Using DNA extracted from different wild and cultivated species of cotton, we analyzed and optimized the parameters for the random amplification of polymorphic DNA (RAPD). All the parameters have an effect on the final result but the concentrations of template DNA, magnesium chloride, deoxynucleoside triphosphates, and the temperature of denaturation seem to be the most important factors. The optimization was performed by successive adjustments of the standard RAPD conditions and by taking into account the manufacturers' recommendations for each reagent. The optimized conditions were then used to assist an interspecific hybridization programme involving two allotetraploid trispecific hybrids (Gossypium thurberi Tod. x G. sturtianum Will.) doubled x G. hirsutum L., designated by G405 and (G. hirsutum x G. raimondii Ulbr.) doubled x G. sturtianum, designated by G376. Both trispecific hybrids were backcrossed with three varieties (LPB5, NC8 and C2) of the cultivated upland cotton G. hirsutum. In RAPD analysis, thirty random decamer primers generated 375 RAPD markers. Analysis of genetic similarity from the RAPD data with UPGMA and Jaccard's distance revealed 78.3-78.7 per cent similarity between the three varieties of G. hirsutum and 31.3-39.2 per cent similarity between G. hirsutum and the wild diploid species (G. thurberi, G. raimondii and G. sturtianum). The genetic similarity within backcross 1 progenies showed values ranging between 63.2-78.0 per cent for the cross G405 x LPB5, 75.0-80.4 per cent for G405 x NC8, 63.9-82.2 per cent for G405 x C2, 76.3-83 per cent for G376 x C2 and 64.9-79.8 per cent for the cross G376 x LPB5. This study allowed to choose within the first backckross progenies having the searched trait, those sharing the highest genetic similarity with the cultivated parent G. hirsutum. Results indicate that RAPD analysis can be used to accelerate the recurrent selection of interspecific materials from backcrosses.