19.4 Mating Systems in Cannabis
Cannabis sativais an obligately outbreeding species under natural conditions and is
dioecious (male and femaleflowers occur on different plants). An estimated 48.7%
of plant species overall are either dioecious or self-incompatible, making them
obligate out-crossers (Igic and Kohn 2006 ). It is also estimated that about 42% of
flowering plants exhibit a mixed mating system in nature. In the most common kind
of mixed mating system, individual plants produce a single type offlower and seeds
may be the result of self-pollination, out-crossing or a mixture of progeny types
(Goodwillie et al. 2005 ). Similarly, in hemp and marihuana strains, there are a range
of possibilities regarding mating systems. Some hemp varieties have been bred to
be monoecious (Small and Cronquist 1976 ), where plants produce both male and
femaleflowers on the same plant. One such variety is ‘Silesia’(licenced by
InnoTech Alberta) where male and femaleflowers can be observed on the same
plant at the same time so that they have the ability to self-pollinate (Fig.19.2).
Most other hemp varieties and all marihuana strains used in commercial pro-
duction are dioecious, where plants produce male and femaleflowers on different
plants. In addition to the phenotypically distinct monoecious and dioecious
Fig. 19.2 Monoecious
flowering seen in hemp
variety‘Silesia’where female
flowers (top, with protruding
stigmas) and maleflowers
(bottom, appearing as buds)
appear together on the same
plant
19 Assessing Genetic Diversity inCannabis sativa... 399