VARIABILITY IN HERB YIELD AND POTENTIALS OF HOREHOUND IN NORTH AMERICA
The main objectives of this program were to determine the variability in yield, morphological traits and the content of active substances in Marrubiurn vulgare population and develop a superior cultivar for commercial production and extraction in Canada. Plants were grown in the fields of the Horticultural Research Station of Laval University, Quebec, Canada from 1992 to 1994. There was great variation within the plant population, in terms of morphology, flowering, chromosome size and the shoot yield. The dry shoot yield varied from 6.2 to 67.9 g/plant, while plants height varied from 15 to 56 cm. Leaf shape was found to vary from round to oval, while the color varied from deep dark green to light silver green. Some plants came to flower as early as three to four weeks after planting, while others started flowering at mid-August, September or not at all. We also found that 3% of the plants which induced flowering had faster and uniform seed set and seed ripening, while others had slow development and only few seeds ripened or not at all. We were able to select and maintain three different lines from the population based on the differences. The shape and size of somatic chromosomes of horehound showed significant variations. Though the chromosomes had stability in number, we found aneuploidy and variations in the shape and size of the chromosomes. Such variations might have contributed to the differences in certain morphological features and developmental variations in the population leading to the evolution of different genotypes of this species. Further screening and tests in field and greenhouses resulted in the identification of three distinctly different cultivars (MAR92, Late-1 and Late-2) of M. vulgare. The content of essential oil in horehound was relatively low and leaves were found to contain more essential oil than flowers or stems.
Letchamo, W., Mukhopadhyay, S. and Gosselin, A. (1996). VARIABILITY IN HERB YIELD AND POTENTIALS OF HOREHOUND IN NORTH AMERICA. Acta Hortic. 426, 601-614
Horehound, variability, selection, growth, commercial cultivation, oil