In the present study, 21 Random Amplification of Polymorphic DNA (RAPD) primers were used to determine the genetic distance among five wheat genotypes varying for salinity tolerance. A total of 178 amplified bands were detected using 21 RAPD primers, out of which 71 were monomorphic and 107 were polymorphic. The total number of bands observed for every primer was recorded separately and the polymorphic percentage was subsequently calculated. The total number of amplified DNA bands varied between 14 (primer OPA-06) and 3 (primer OPG-08) with an average of 8.48±1.15 bands per primer. The maximum number of polymorphic bands (14) was obtained for primer OPA-06 and minimum number (1) for primer OPG-08. The percentage polymorphism ranged from as low as 18.18% (primer OPB-18) to as high as 100% (primers OPB-14, OPH-01, OPH-20, OPA-06, OPH-11, OPO-06 and OPI-17). Average polymorphism across all the five wheat varieties was found to be 60.11±2.87. A significant correlation (0.564, p<0.01) was observed between the total number of bands and the number of polymorphic bands amplified by 21 RAPD primers. Similarly, the matrices of five wheat genotypes revealed the relationship among them. Genotypes KH-65 and DI-103 were the closest, followed by KRL-19 and Tordo, while DI-101 was the most distant. Genotype-specific primers have the potential to be used further in varietal identification and classification.

An increased salt tolerance is needed for the wheat crop grown in the salt affected areas and those at risk of salinization. This requires new genetic sources of salt tolerance and more efficient techniques for identifying the salt tolerant germplasm, so that new genes for tolerance can be introduced into crop cultivars. Considerable genetic variability exists in wheat germplasm for salt tolerance. Since, the genes for salt tolerance are scattered over a multitude of pure lines, it is imperative to develop wheat varieties combining high per se performance with salt tolerance so as to sustain wheat production in salt affected areas. However, breeding for salt tolerance has been limited because: (a) tolerance to stress is controlled by many genes and their simultaneous selection is difficult (Richards, 1995; and Flowers et al., 2000); (b) tremendous effort is required to eliminate the undesirable genes that are also incorporated during breeding (Richards, 1995); and (c) there is a lack of efficient selection procedures particularly under field conditions.

Molecular marker techniques offer a wide range of novel approaches for improving the efficiency of selection strategies. These techniques are based on the detection of sequence variations among varieties or accessions of different crop species. Sequence variations are generally abundant so that almost an unlimited number of such markers are available. Molecular markers have an advantage over the traditional phenotypic markers as they are heritable, refractory to environmental variations as well as developmental stages and available in abundant numbers which increases their power of discrimination (Miller and Tanksley, 1990). Modern molecular techniques offer new approaches for improving the salt tolerance in crops. Most likely a combination of old and new approaches will be the most productive. Identifying physiological traits and key genes and understanding the mechanisms at the cellular and whole plant level are central to all approaches. Therefore, the present investigation was undertaken to characterize wheat genotypes differing for salt tolerance using molecular markers.

Genotypic Variability,Wheat Genotypes, RAPD Markers, Polymorphism, Random Amplification of Polymorphic DNA , RAPD,Triticum aestivum, Cetyl Trimethyl Ammonium Bromide, CTAB, Polymerase Chain Reaction, PCR, Electrophoresis in Tris-Borate Ethylenediaminetetraaceticacid, EDTA, Unweighted Pair Group Method with Arithmetic Averages, UPGMA.