The sources of male sterility include

The sources of male sterility include failure of another dehiscence, nonfunctional pollen grains, etc.
But it is not caused by Spontaneous mutations, Induced mutations, and Interspecific crosses.
Male sterility (CMS), a condition under which a plant is unable to produce functional pollen, is widespread among higher plants.
Male-sterility plants provide crucial breeding tools to harness hybrid vigor, or heterosis, in hybrid crops and also provide important materials to study stamen and pollen development and cytoplasmic-nuclear genomic interactions.