Identification of ISSR and RAPD Molecular Markers Associated with Agronomic Traits in Lemon Balm (Melissa Officinalis)

Finding association between molecular markers and agronomic traits provides an excellent tool for indirect selection of a trait of interest in the population. In this study, stepwise regression analysis was used to estimate associations between ISSR and RAPD markers with some agronomic traits in 12 lemon balm ecotypes. Markers or bands were considered as independent variables and traits were considered as dependent variables. The results analysis revealed significant associations between the traits and some of the studied loci. For all the traits more than one informative marker was detected. Totally 90 informative markers including 48 ISSR loci and 42 RAPD loci were identified. Four RAPD markers (SA-R-10, OPA-01-15, OPC-04-7 and CS-56-8 markers with 54%, 0.7%, 0.4% and 0.2% phenotypic variation, respectively) and four ISSR markers (UBC826-1, UBC812-9, UBC813-10 and UBC825-4 markers with 29%, 7.5%, 5% and 3% phenotypic variation, respectively) showed a significant correlation with Essential oil percentage and controlled 99.8% of the phenotypic variation. These markers are considered to be relatively more reliable. Among the RAPD primers, special attention should be drawn to primer SA-R, which had the highest associated fragments with the traits including days to 50% flowering, number of branches per plant, vegetative fresh weight and dry weight. Some of these markers (SA-R and UBC813 primers) were associated with more than one trait that these traits had very close linkage together or possibly were controlled by pleiotropic effects. These primers have been found useful for improved lemon balm breeding programmers.