Male Sterility and Restorer Genes in Maize

Abstract

Male-sterile plants are those that fail to produce functional pollen grains. In maize, male sterility can result from either nuclear or mitochondrial gene mutation. The former is referred to as genic male sterility and the latter as cytoplasmic male sterility (CMS). Over 20 nuclear gene mutations that confer a male-sterile phenotype have been identified. (see Neuffer et al. 1993.) The majority of these are recessive and have been assigned the symbol ms (Ms for the dominant genes). Some mutations that produce aberrant cell or chromosome behavior, e.g., asynaptic (as) and ameiotic (am), may also result in male sterility. In contrast, only three major categories of CMS have been recognized—cms-C (Charrua), cms-T (Texas), and cms-S (USDA). (See reviews by Duvick 1965; Edwardson 1970; Laughnan and Gabay-Laughnan 1983; Newton 1988.) Genic male sterility is inherited according to Mendelian rules whereas CMS is transmitted maternally. Plants carrying one of the CMS-type cytoplasms are male-sterile unless they also carry a dominant nuclear restorer-of-fertility gene(s).