Sexual Reproduction in Castor Bean

Abstract

Castor bean (Ricinus communis L.) is an important industrial oilseed crop with diverse sex patterns. Understanding the genetics and genomics of castor bean sexual reproduction is valuable for both its breeding and sex-determination researches. Here, we described the biology of flowering habit, sex forms, and sex variations in castor bean. Castor plant grows to raceme–cyme inflorescence and has the potential to be an ever-flowering perennial, it is normally monoecious raceme, but other inflorescence patterns such as pistillate, male, and intersperse also can be observed. A simplified overview on wide variation of sex tendency and variegation phenomenon in sex expression was given, and the factors affected sex expression were also summarized. Moreover, sex inheritance was also generalized, and the genes underlying or involved in the monocism, female, interspersed staminate flowers, and terminal hermaphroditism were mentioned. We reviewed the genetic variation of the replication for pistillate plant by the combination of tissue culture, molecular markers, and conventional breeding. It was showed that pistillate somaclones with high percentage of pistillate plants were obtained, and allelic differences were discovered among individuals of somaclonal populations with instable sex expression. Some genes associated with sex expression and reproduction, hormone response, transcription regulation and signal transduction, have also been identified by digital gene expression (DGE) analysis. This overview provided some information and valuable hints for insights into the molecular mechanism of sex determination.