Abstract
The results of crossing experiments between a dihydrocarvone type of Ment h a suaveolens (Mentha suaveolens 12) and piperitone oxide types of resp. Mentha longifolia (M. longifolia 3) and Mentha suaveolens (M. suaveolens 6) and of two backerossing experiments are given.
Morphologically the hybrids stood midway between the parent plants. Chemical analysis showed that in all cases the formation of dihydrocarvone was dominant over the formation of piperitone oxide and that M. longifolia 3 and M. suaveolens 6 are recessive for the same gene. Starting from a compound like diosphenolene, with an oxygen function both at C–2 and at C–3, and which is present when the gene c is homozygously present, substitution of the gene c by the dominant C involves reduction of the oxygen at C–3 leading to C–2 oxygen compounds like carvone. In ccaa types substitution of the gene a by the dominant gene A will involve the reduction of the oxygen at C–2 leading to C–3 oxygen compounds like piperitenone.
The gene C is supposed to be epistatic over A. This explanation seems more likely than the one previously given by Murray (1960b) at which the dominant gene C is held responsible for the oxydation of a monoterpene hydrocarbon (limonene) at C–2 leading to carvone etc. and its recessive allele is responsible for the oxydation at C–3 leading to piperitenone etc. whereas the dominant gene A involves the reduction of the double bond 1,2 of piperitenone (–pulegone) and piperitone (( menthone). A scheme is discussed in which a dominant gene P is held responsible for the saturation of the double bond 4,8 (Murray et al., 1971) and in which a hypothetical, dominant gene is responsible for the saturation of the double bond 1,2 of piperiteno?ie and of the double bond 1,6 of carvone.
