Background: understanding molecular diversity in Lactuca species is substantial for the management, improvement and efficient uses of their accessions. Therefore, this work aimed to evaluate molecular diversity among and within Lactuca species. Methods and Results: the molecular diversity was assessed using isozymes and RAPD analyses that gave 87.09% and 100% polymorphic percentages respectively, indicating a high genetic variation within and among Lactuca species. The number of alleles were higher in the wild species compared to the cultivated species, reflecting a reduction in the richness of alleles in the cultivated species due to domestication that caused a reduction in genetic diversity to meet the demand for high crop productivity. Isozymes and RAPD clustering dendrogrames: (1) separated, L. sativa accessions in more than one cluster confirming their polyphyletic origin; (2) collected the accessions of L. viminea in one cluster revealed its homogeneity; and (3) divided the accessions of L. saligna in two clusters varied in the number of alleles, particularly “A” form. The corresponding analysis associated the accessions of the wild species based on “B” form of the alleles of the tested isozymes, and the cultivated species on the forms “A” and “C”, suggesting that: (1) allele “B” might be the primitive form of these loci that can tolerate the environmental stresses which prevails in the habitats of the wild species, and (2) forms “A” and “C” could be the derived forms. Conclusions: These results are of great interest for the management of Lactuca germplasm and for future breeding programs of lettuce.

Understanding of the molecular basis of genetic diversity in Lactucaaccessions is substantial for the management, improvementand efficient uses of Lactuca accessions. Therefore, this workaimed to evaluate molecular diversity among twenty-six accessions of Lactuca species usingisozymes and RAPD analyses. The polymorphic percentages were 87.09%and 100% in isozymes and RAPD analyses respectively, indicating a high genetic variation within and among Lactuca species. The number of alleles were higher in the wild species compared to the cultivated species, reflecting a reduction in the richness of alleles in the cultivated species due to domestication that caused a reduction in genetic diversity to meet the demand for high crop productivity.Isozymes and RAPD clustering dendrogrames: (1) separated,L. sativa accessions in more than one cluster confirming their polyphyletic origin; (2)collected the accessions of L. vimineain one cluster revealed its homogeneity; and (3) divided the accessions of L.saligna in two clusters varied in the number of alleles, particularly “A” form. The corresponding analysis associated the accessions of the wild species based on the alleles “B”of the tested isozymes and the cultivated species on alleles “A” and “C”, suggesting that: (1) allele “B” might be the primitive form of these loci that can tolerate the environmental stresses which prevails in the habitats of the wild species, and (2) “A” and “C” could be the derived forms. These results are of great interest for the management of Lactuca germplasm and for future breeding programs of lettuce.