RESUMO

Finding association between molecular markers and agronomic traits provide 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 lemon balm ecotypes. The analysis of results revealed significant associations between the traits and some of the studied loci. For all the traits, more than one informative marker was detected. Totally,90informative markers, including 48 ISSR loci and 42 RAPD loci, were identified. The SA-R-10, UBC826-1, UBC812-9, UBC813-10, UBC825-4, OPA-01-15, OPC-04-7 and CS-56-8 markers or fragment showed a significant correlation with Essential oil percentage and controlled 99.8% of the phenotypic variation. These markers are 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 for 50% flowering, number of branches per plant, fresh weight and dry weight. Some of ISSR and RAPD markers were associated with more than one trait in multiple regression analysis that may be due to pleiotropic effect of the linked quantitative trait locus on different traits or its linkage to different genes. These primers have been found useful for improved lemon balm.(AU)

Encontrar associação entre marcadores moleculares e traços agronômicos é uma excelente ferramenta para seleção indireta de um traço de interesse na população. Neste estudo, foi utilizada a análise de regressão stepwise para estimar associações entre marcadores ISSR e RAPD com algumas características agronômicas em ecótipos de erva cidreira. A análise dos resultados revelou associações significativas entre os traços e alguns dos loci estudados. Para todos os traços mais de um marcador informativo foi detectado. Foram identificados 90 marcadores informativos, incluindo 48 loci ISSR e 42 loci RAPD. Os marcadoresou fragmentos SA-R-10, UBC826-1, UBC812-9, UBC813-10, UBC825-4, OPA-01-15, OPC-04-7 e CS-56-8 mostraram uma correlação significativa com a percentagem de óleo essencial e controlaram 99,8% da variação fenotípica. Estes marcadores são considerados relativamente mais confiáveis. Entre os primers RAPD, destaca-se o primer SA-R, que apresentou os maiores fragmentos associados com as características, incluindo dias para 50% de floração, número de ramos por planta, peso fresco e peso seco. Alguns dos marcadores ISSR e RAPD foram associados a mais de um traço na análise de regressão múltipla que pode ser devido ao efeito pleiotrópico do locus de traço quantitativo ligado em diferentes traços ou sua ligação a diferentes genes. Estes iniciadores provaram ser úteis para o melhoramento da erva cidreira.(AU)

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RESUMO

Lemon balm (Melissa officinalis) is a medicinal plant that is widely used as a sedative or calmant, spasmolytic and antibacterial agent and sleep aid. This has led to a high demand for lemon balm products, resulting in the extinction of this species in some of its natural habitats. Molecular techniques have increasingly been used in plant diversity conservation and isolation of PCR amplifiable genomic DNA is an important pre-requisite. Lemon balm contains high levels of polyphenols and polysaccharides, which pose a major challenge for the isolation of high-quality DNA. We compared different genomic DNA extraction protocols, including traditional phenol-chloroform DNA extraction protocols and two commercial kits for DNA purification for their ability to produce good-quality DNA from fresh leaves of five lemon balm genotypes. Quality and quantity of the DNA samples were determined using 0.8% agarose gel electrophoresis and a spectrophotometer. The DNA purity was further confirmed by PCR amplification using barley retrotransposon LTR base primers. The spectral quality of DNA as measured by the A(260)/A(280) ratio ranged from 1.46 to 2.37. The Fermentase genomic DNA purification kit and the CTAB extraction protocol using PVP and ammonium acetate to overcome the high levels of polyphenols and polysaccharides yielded high-quality DNA with a mean A(260)/A(280) ratio of 1.87. The quantity of DNA and its PCR purity were similar with all the protocols, but considering the time and cost required for extraction of DNA from a large number of samples, the CTAB protocol using PVP and ammonium acetate is suitable for lemon balm.

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