Male sterility in plants

Sterile male plants are plants that fail to produce functional pollen resulting in the inability to self-fertilize or contribute pollen for fertilization. Male sterility can arise from genetic mutations in either the nuclear or cytoplasmic genomes, developmental defects in anther or pollen formation, or environmental factors. Naturally occurring male sterility systems, as well as engineered approaches, are widely used in plant breeding to facilitate the production of hybrid seed. Pollen development is highly sensitive to environmental conditions, with heat stress posing a significant and increasing challenge in crop production. High day or night temperatures can trigger male sterility, resulting in reduced seed or fruit set and yield. Even a short episode of elevated temperature can disrupt anther development, often by causing premature degeneration of the tapetum or impairing its ability to nourish developing pollen.

In cytoplasmic male sterility (CMS), defects in mitochondrial gene expression disrupt normal anther and pollen development, often through impaired function of the tapetum, a nutritive tissue required for pollen maturation. CMS systems are widespread in flowering plants and have been extensively exploited in crop breeding to facilitate hybrid seed production. In some engineered systems, targeted genetic approaches have been used to selectively disrupt tapetal function to induce male sterility. The mutations cause the breakdown of the mitochondria in these specific cells and result in cell death and so pollen production is interrupted.