Male sterility in onion (Allium cepa L.): origin: origin, evolutionary status, and their prospectus

Onion (Allium cepa L.) is the most diversified crop of the family Alliaceae; it is in cultivation since from ancient era for its edible bulbs and verdant foliage due to the immense nutritional and medicinal properties. The increased social acceptance of bulb onion in daily diet could lead to an increase in cultivable area with a similar bulb production. However, the output per unit area had limited due to the lack of exploitation of heterosis for bulb yield. The only possibility to increase the onion productivity is to increase the volume of the individual bulb, and it can achieve by exploiting heterosis for earliness, biotic and abiotic stress resistance, bulb weight, and size by the development of hybrid with the use of male sterility mechanisms like cytoplasmic-genic male sterility or cytoplasmic male sterility system in onion. The male sterility trait is precious in heterosis breeding due to its potential advantages in the development of onion hybrids. In these perspectives, the present review reveals the origin, evolution, maintenance, and prevalence of male sterility systems of onion and the technique of identification of the male sterility systems. The polymorphisms between male-sterile and male-fertile phenotypes difference with morphological-molecular markers with the marker-phenotype linkage of onion.