Oil composition of Mentha aquatica-M. longifolia F1 hybrids and M. dumetorum

Summary If M. aquatica (2n=96) having the genotype cc AA ff RR, 60–80% menthofuran, but almost no menthone, menthol, and menthyl acetate is hybridized with M. longifolia (2n=24) having the genotype cc aa FF rr, 4–5% piperitone and 66% piperitone oxide all F₁ hybrids have the genotype cc Aa Ff Rr. They also differ from either parent in having about 1.2–5.5% menthone, 4–42% menthol, 2–20% menthyl acetate, and usually only 1–7% menthofuran. However a few individuals may have as much as 41% disomenthone, 6% pulegone, 45% menthofuran or 10% beta-caryophyllene. M. dumetorum, considered by taxonomists to be a natural M. aquatica-M. longifolia F₁ hybrid, has the same 14 oil constituents observed in the experimentally produced hybrids. Thirteen of the oil constituents of the single M. dumetorum strain are within the quantitative range of 9 highly variable hybrids. The 17% pulegone of the natural strain was higher than the 6% observed in the hybrids. The M. aquatica-M. longifolia F₁ hybrids have the same major oil constituents as M. piperita but in very different quantitative proportions. Since the sporophytic chromosome number of M. dumetorum has been reported as 72, 84, or 96, the suggestion is made that some strains are secondary hybrids from backcrossing and that others with 72 chromosomes may be F₁ hybrids between M. aquatica and piperitone strains of M. spicata or M. crispa. Hybrids with polyploid M. longifolia are not greatly different in oil composition.