Cytoplasmic Male Sterility (CMS) & Cytoplasmic Genetic Male Sterility (CGMS)/Pollination Control

This type of male sterility is determined by the cytoplasm . CMS is the result of mutation in the mitochondrial genome (mtDNA), which leads to an unfavourable nuclear-mitochondrial interaction or incompatibility, the ultimate consequence of which is male sterility. The mtDNAs of male sterile lines show mutations, novel gene organisation or new open reading frames corresponding to chimaeric genes produced by duplication and rearrangement of mtDNA sequences, the last change being the most common, e.g., in CMS-T of maize and Kagura CMS of brassicas. These changes alter the types of polypeptides produced in mitochondria, which may result in male sterility if a critical function were adversely affected, Some of the mutant mitochondrial genes associated with male sterility have been characterised, the alteration was found to be distinct for each species and cytoplasm type. In some plant species, e.g., tobacco, barley, sorghum and rapeseed, chloroplast genome has also been implicated in male sterility.
Cytoplasmic male sterility may be transferred easily to a given strain by using that strain as the recurrent pollinator parent in the successive generations of a backcross programme. After 6-7 backcrosses, the nuclear genotype of male sterile line would become almost identical to that of the recurrent pollinator strain. This male sterile line is now maintained by crossing it with the pollinator backcross programme. Such a male fertile line is known as the maintainer line or B line as it is used to maintain the male sterile line, also known as the A line.
Cytoplasmic male sterility may be utilized for producing hybrid seed in certain ornamental species, or in species where a vegetative part is of economic value. But in those crop plants where seed is the economic part, it is of no use because the hybrid progeny would be male sterile.

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