Peanut (Arachis hypogea L.) is one of the important oil and protein crops in the world. Peanut breeders in the USA have successfully developed hundreds of improved cultivars [1] . Knowledge of diversity patterns will allow breeders to better understand the evolutionary relationships among accessions, to sample germplasm in a more systematic fashion, and to develop strategies to incorporate useful diversity in their breeding programs [2] .

Different approaches were used to assay genetic diversity in crop plants including morphological traits, and isozyme electrophoresis, however, these techniques are insufficient to serve as accurate markers due to environmental influences on morphological traits and insufficient polymoprhism produced among closely related genotypes [3] .

Certain properties are desirable for a molecular marker such as highly polymorphic behavior, co dominant inheritance, and frequent occurrence in the genome, even distribution throughout the genome, selectively neutral behavior, easy access, easy and fast assay and high reproducibility [4] [5] . Examples of such DNA molecular markers are: random amplified polymorphic DNA (RAPDs) [5] [6] .

RAPD markers had proved to be good genetic markers to assay and evaluate the genetic diversity between and within the same species, populations and individuals [6] . RAPD marker depends on the amplification of DNA sequence by polymerase chain reaction using only a single primer of arbitrary nucleotide sequence. The technique has proved to be fast and simple needs small quantities of template DNA, beside its ability to detect relatively small amounts of genetic variation [7] [8] .

The objectives of this study were to characterize the molecular diversity of the peanut accessions by analyzing the DNA amplification products using RAPD molecular markers, evaluate RAPD method to be used in peanut as genetic markers and improve such techniques as suitable strategies for peanut germplasm characterization.

Out of a total of 220 amplification products (0.2 to 4 kilo base pairs) using twenty-seven primers, 80 (36.4%) were polymorphic and 140 products were shared among all genotypes (not polymorphic). The twenty-four primers (OPA-02, OPA-03, OPA-04, OPA-05, OPA-07, OPA-09, OPA-10, OPA-11, OPA-12, OPA-13, OPA-14, OPA-15, OPA-16, OPA-17, OPA-18, OPA-19, OPA-20, OPB-03, OPB-04, OPB-05, OPB-06, OPB-07, OPB-10, OPB-11, OPB-12) produced different banding patterns for all genotypes. While sixteen primers (OPA-01, OPA-06, OPA-08, OPB-01, OPB-02, OPB-08, OPB-09, OPB-13, OPB-14, OPB-15, OPB-16, OPB-17, OPB-18, OPB-19 and OPB-20) detected no polymorphism although they did successfully amplify a range of monomorphic bands.

Two major clusters resulted: One cluster included by itself (S1 to S8) and the second cluster included the rest of the accessions (S9 to S20). The third cluster had the two out groups of Arachis duranensis (Figure 1). The genetic distance between first and the second cluster was 6.6.

Cluster analysis of each RAPD profiles (Figure 1) showed that a significant genetic variation was detected in peanut accessions which could reflect different genetic background. Moreover, cluster analysis showed that samples S1 to S8 and S9 to S20 were genetically close (they showed 96% similarity).

The dendrogram (Figure 1) showed that the RAPD methodology was sensitive enough to detect low levels of variation in peanut accessions.

The current study aimed on using the PCR-based protocols to assess genetic variability and to fingerprint genotypes of peanut. Random amplified polymorphic DNA (RAPD) had been used effectively to assess the amount of genetic diversity in germplasm collections. Using wheat, barley, rye and wheat-barley addition lines, Weining and Langridge (1991) detected polymorphism using conserved, semi random and random primers [4] . With different combinations of primers, they were able to detect both inter and intra specific diversity. In this study it was possible to show that the amplification products from 27 random primers (RAPD assay) were sufficient to discriminate among individual genotypes of peanut.

Few genetic studies have been conducted on peanut cultivars. In recent studies, fingerprints based on different markers were compared using genotypes from different species. There were both agreements and disagreements in findings based on different markers and species: The study of Brassica oleracea by Lanner-Herrera et al. (1996) [11] , a moderate spearman’s rank correlation (r = 0.38) between RAPD and isozyme distances was found. Russell et al. (1997) [12] compared the levels of genetic variation among barley accessions revealed by RFLP, AFLP, SSR, and RAPD, and reported that when the spearman’s rank correlation was used, the correlation between SSR and RAPD was 0.235, the highest correlation was found between RFLP and AFLP (0.708).

Because of the low number of the genetic studies and the poor resolution of some employed molecular markers in these studies, more studies like the current study need to be done in order to evaluate and estimate the ge-

netic diversity in the peanut germplasm.

In conclusion, this study reported a successful fingerprinting of peanut accessions using RAPD and demonstrated the usefulness of these markers in estimating the extent of genetic variation in peanut germplasm. The current results are supported by many recent molecular studies [13] [14] .

The use of RAPD markers in Arachis must be further continued in order to drive specific linkage between RAPD markers and genes controlling agronomically important characters. These diagnostic molecular tools will greatly assist in the identification of new and different sources of diversity which may help breeders to decide what genotypes to cross for making new genetic combinations and to determine which genetic resources should be retained in a collection in order to conserve maximum genetic diversity in the gene bank.

The authors are grateful for US Department of Agriculture for providing the peanut cultivars and for Ohio University Zanesville for funding this project.

MohannadG. Al-Saghir,Abdel-SalamG. Abdel-Salam, (2015) Genetic Diversity of Peanut (Arachis hypogea L.) Cultivars as Revealed by RAPD Markers. American Journal of Plant Sciences,06,2303-2308. doi: 10.4236/ajps.2015.614233