Review on different mechanisms of sex determination and sex-linked molecular markers in dioecious crops: a current update

Flowering plants are known to exhibit vast diversity of sexual systems encompassing bisexual, monoecious and dioecious conditions. Dioecy offers opportunities to explore separately the male and female programmes giving an insight to the evolutionary, developmental and molecular processes leading to separate mechanisms for sex expression. Mechanisms controlling sex can either be genetic or epigenetic (physiological and environmental). Plant hormones too influence sex expression. An active Y sex determination system and an X to autosomes ratio systems are common amongst the flowering plants. Advances in our understanding of sex determination has been addressed both by conventional as well as molecular approaches. Using conventional techniques mainly cytogenetics, sex chromosomes in some dioecious plants have been identified and characterized. Surprisingly, the presence of well defined sex chromosomes was found in only few species. Some sex linked genes have also been identified and characterized using molecular approaches but none of these genes have a direct link to sex determination. Molecular markers have been employed to resolve the enigma associated with dioecism to a certain extent. Its application in plant breeding is immensely beneficial. Positively, it would be beneficial for validation of sex prior their sex expression at larger perspectives. The present review therefore emphasizes the mode of sex determination among dioecious plants vis-a-vis summarizes the works related to gender specific markers generated using male and female plants from agriculturally important dioecious crops.