MECHANISMS OF GENIC MALE-STERILITY

For normal sexual reproductive development, coordination must occur between both male and female organ ontogeny. An abnormality at any point in this process may lead to sterility. Classification of sterilty can be divided into heritable and nonheritable sterility. Numerous schemes for mechanisms controlled by nuclear genes (genic male sterility) have been devised to identify the timing and location of the inception of sterility. These schemes are divided into structural (gross organ changes) and functional. The latter may be divided into abnormal changes occurring in the male cells or surrounding anther tissues during microsporogenesis. Even though sterility can be produced by chemicals, ionizing radiation, genetic engineering, etc., the primary examples presented here will be of naturally occurring systems. The objectives of this paper are to review heritable genic male sterility, give examples of naturally occurring genic male sterility systems, and identify their uses and proposed applications in plant breeding.