Discovering the epigenetic mechanisms and factors that influence sex change in dioecious cannabis.

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Cannabis (Cannabis sativa L.) has a long history of human use for a variety of applications including fibre, food, medicine, and for its psychoactive properties. Cannabis is an annual dioecious species with separate male (XY) and female (XX) plants. In cannabis, sexual dimorphism occurs in a late stage of plant development (i.e., flowering) accompanied by a morphological dimorphism. In general, females produce compact and rarely lax inflorescence with flowers on the main shoot and short lateral branches, while males produce an inflorescence in the form of loose terminal and axillary panicles. It is considered that cannabis has one of the most complicated mechanisms of sex determination and sex inheritance among dioecious plants. While the genetic determinism of sex in cannabis is considered an important heritable trait for genetic improvement, its sexuality is not well known, is plastic and can be changed. In addition to environmental factors, application of exogenous plant growth regulators or inhibitors can modify or reverse sex morphology in cannabis. In view of this, I hypothesize that sex is not determined by particular chromosomes, but by the whole genome, and by the gene and chromosome interactions. Thus, all individuals are able to express one or the other sex. As a result, the fundamental question arising here is "how genetic and epigenetic factors interact and regulate sex expression in cannabis?" Therefore, here I propose to find answers to this fundamental question which has major implications for understanding the biology of sex in cannabis and its application for genetic improvement. Insights from this proposal will also shed light on other commercially important dioecious crops such as asparagus, papaya, and hops.