IM not 100% exactly sure if im completely correct on this topic however here is my input. Cannabis and other types of trees are all in a similar group because of one specific trait that they all entail. Ofcourse this trait is called terpins. Terpins in resin is how the actual content of flavinoid's and smell is measured. With cannabis there are 4 main groups that the terpins resemble when we taste them.
1. Sweet 2. Sour 3. Spicy 4. Bitter.
Here is some information from Greenhouse Seed Companys site... they are starting to measure the Terpins in resin in combination with the other cannabis resin values.
These are some basic Terpin's found in cannabis.
Alpha-Pinene is an organic compound, found in the oils of many species of many species of pine trees. It is also found in the essential oil of rosemary (Rosmarinus officinalis). 2 types of Alpha-pinene exist in nature, one more common in European pines, the other more common in North America. A mix of the two is present in the oil extracted from the eucalyptus tree. In the Green House range this terpene is at the highest level in the Super Silver Haze. So if you like pine-tree smelling and tasting weed, think of growing this strain, or use it for crossings.
Limonene is a hydrocarbon, classified as a cyclic terpene. It is a colourless liquid at room temperatures with an extremely strong smell of oranges. It takes its name from the lemon because lemon and other citrus fruits contain high quantities of this compound, which is responsible for much of their smell.
Sabinene is a natural monoterpene and it is isolated from the essential oils of a variety of plants, mostly oak trees. Sabinene is one of the chemical compounds that contributes to the spiciness of black pepper and is a major constituent of carrot seed oil. It also occurs in tea tree oil at a low concentration. Again, this terpene is high in the Super Silver Haze
Myrcene, or β-myrcene, is also an organic compound. It is classified as a hydrocarbon and a monoterpene. It is obtained from the essential oil from various plants: bay, verbena, myrcia (from which is gets its name) and others. Myrcene is one of the most important chemicals used in the perfumery industry. Because of its pleasant odor, it is occasionally used directly. But it is also highly valued as an intermediate for the preparation of flavor and fragrance chemicals such as menthol, citronella, and geraniol. It is extremely high in the White Widow.
Also... cannabis has the most combined terpins than any other plant on earth ... most of the strainds I grow have about 15 dominate terpins which make up their flavour and smell content. Just remember to research about everything... especially if you are truely interested and especially if you want to bred a wonderfull masterpeice!