An overview of cytoplasmic male sterility in Brassica napus

Rapeseed (Brassica napus ) is one of the world's most important oilseed crops, supplying humans with oil products, nutritious feed for livestock, and natural resources for industrial applications. Due to immense population pressure, more seed production is needed for human consumption due to its high quality of food products. As a vital genetic resource, male sterility provides ease in hybrid seed production and heterosis breeding. Better utilization of male sterility requires understanding its mechanisms, mode of action, and genes involved to be characterized in detail. Cytoplasmic male sterility (CMS) has been reported in many plant species and is a maternally inherited trait that restricts viable pollen development and production. The mitochondrial genome is involved in the induction of male sterility, while the nuclear genome plays its role in the restoration. Presently, rapeseed has more than 10 CMS systems. Pol-CMS and Shaan2A are autoplasmic resources that arose via natural mutation, while Nap-CMS and Nsa-CMS are alloplasmic and were created by intergeneric hybridisation. In this review, we discuss the types of male sterility systems in rapeseed and provide comprehensive information on CMS in rapeseed with a particular focus and emphasis the types of CMS in rapeseed.