Fertile grounds: exploring male sterility in cotton and its marker development

The high cost of producing conventional hybrid cotton seeds led to more research efforts on cotton male sterility systems. There is a lack of studies on cytology, histology, morphological variation, yield, and altered restorer backgrounds to identify and develop male sterility markers in cotton hybrids. Hybrid cotton can be efficiently produced by exploiting genetic male sterility. Among the 19 Genetic Male Sterility (GMS) genes discovered, the lines with ms5ms6 genes are mostly utilised to establish successful hybrid cotton in India. Molecular markers closely associated with the MS alleles are identified to facilitate the efficient and rapid backcrossing of male-sterility genes into elite lines or cultivars by marker-assisted backcrossing. The majority of the markers which are random DNA markers (RDMs), are probably lost, when recombination occurs. In contradiction, molecular markers (functional markers, or FMs) within the genic region can be identified and employed in crops for diverse traits, if prospective characteristic genes are known. In this review, the mechanism of male sterility, its gene expression level, and the need for functional markers for the male sterility trait in cotton have been put forward.