Abstract
Melilotus albus and Melilotus officinalis are widely used in forage production and herbal medicine due to the biological activity of their coumarins, which have many biological and pharmacological activities, including anti-HIV and anti-tumor effects. To comprehensively evaluate M. albus and M. officinalis coumarin content (Cou), morphological variation, and molecular phylogeny, we examined the Cou, five morphological traits and the molecular characterization based on the trnL-F spacer and internal transcribed spacer (ITS) regions of 93 accessions. Significant (p < 0.05) variation was observed in the Cou and all five morphological traits in both species. Analysis of population differentiation (Pst) of the phenotypic traits showed that powdery mildew resistance (PMR) had the greatest Pst, meaning that this trait demonstrated the largest genetic differentiation among the accessions. The Pst values of dry matter yield (DMY) and Cou were relatively high. Biplot analysis identified accessions with higher DMY and higher and lower Cou. Analysis of molecular sequence variation identified seven haplotypes of the trnL-F spacer and 13 haplotypes of the ITS region. Based on haplotype and sequence analyses, the genetic variation of M. officinalis was higher than that of M. albus. Additionally, ITS sequence analysis showed that the variation among accessions was larger than that among species across three geographical areas: Asia, Europe, and North America. Similarly, variation among accessions for both the trnL-F and ITS sequences were larger than the differences between the geographical areas. Our results indicate that there has been considerable gene flow between the two Melilotus species. Our characterization of Cou and the morphological and genetic variations of these two Melilotus species may provide useful insights into germplasm improvement to enhance DMY and Cou.
Highlights
Coumarins, a class of structurally unique and important natural compounds, exist in many plant species in Nature [1,2,3] and present potential medicinal value [4]
There was a wide range of variation for each of the traits
There were some differences between M. officinalis accessions and M. albus accessions
Summary
A class of structurally unique and important natural compounds, exist in many plant species in Nature [1,2,3] and present potential medicinal value [4]. Many medicines containing coumarin-based compounds such as warfarin and phenprocoumon are often not linked to Molecules 2018, 23, 810; doi:10.3390/molecules23040810 www.mdpi.com/journal/molecules. The coumarin-derivative prehispanolone from Chinese motherwort (Leonurus cardiaca) reduces fibrinogen and blood viscosity and inhibits platelet aggregation [6]. These functions make coumarins important medicinal compounds. Coumarin is a plant secondary metabolite in Melilotus [7], and its content varies significantly among different Melilotus species, with mean contents ranging from 0.06 to 0.753% of dry matter [8].
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