Molecular phylogeny of Gossypium species by DNA fingerprinting

Total genomic DNA from 31 available Gossypium species, three subspecies and one interspecific hybrid, were analysed to evaluate genetic diversity by R APD, using 45 random decamer primers. A total of 579 amplified bands were o bserved, with 12.9 bands per primer, of which 99.8% were polymorphic. OPJ-1 7 produced the maximum number of fragments while the minimum number of frag ments was produced with primer OPA-08. Cluster analysis by the unweighted p aired group method of arithmetic means (UPGMA) showed six main clusters. Cl uster 'A' consisted of two species and one subspecies of the A-genome, with a 0.78-0.92 Nei's similarity range. Cluster B, composed of all available t etraploid species and one interspecific hybrid, showed the same sister clus ter. Nei's similarity ranged from 0.69 to 0.84. The B-genome formed the UPG MA sister cluster to the E-genome species. Cluster 'C' consisted of five Go ssypium species of which three belong to the B-genome, with Nei's similarit y values of 0.81 to 0.86. Although there was considerable disagreement at l ower infra-generic ranks, particularly among the D-genome (diploid New Worl d species) and C-genome (diploid Australian species) species. The sole F-ge nome species Gossypium longicalyx was resolved as a sister,group to the D-g enome species. Gossypium herbaceum and G. herbaceum Africanum showed the ma ximum Nei's similarity (0.93). Minimum similarity (0.29) was observed betwe en Gossypium trilobum and Gossypium nelsonii. The average similarity among all studied species was 50%. The analysis revealed that the interspecific g enetic relationship of several species is related to their centre of origin . As expected, most of the species have a wide genetic base range. The resu lts also revealed the genetic relationships of the species Gossypium hirsut um to standard cultivated Gossypium barbadense, G. herbaceum and Gossypium arboreum. These results correspond well with previous reported results. The level of variation detected in closely related genotypes by RAPD analysis indicates that it may be a more efficient marker than morphological marker, isozyme and RFLP technology for the construction of genetic linkage maps.