Summary

Nuclear encoded, genie male sterility (GMS) is a common occurrence in angiosperms and is reported in nearly every major crop species. GMS can result from mutations in any one of a number of genes controlling pollen and/or stamen development and, accordingly, the phenotypes of GMS mutants vary. There are a number of cytological, physiological, and biochemical processes affected in GMS mutants, but the causative mechanisms of GMS are not clearly understood. Although GMS is not commonly used in hybrid seed production, primarily because of the maintenance of pure male-sterile lines, there are several proposals put forward to circumvent these problems. One promising approach is to select for chemical- or environment-sensitive GMS lines in which fertility can be restored by appropriate treatments. Such systems are potentially useful in hybrid seed production.

Introduction

Normal development of the male reproductive organ (stamen) and male gametophyte (pollen grain) is essential for the successful completion of sexual reproduction in angiosperms. Abnormalities at any stage of stamen and pollen development can result in male sterility.

Male sterility is a wide occurrence in flowering plants and has been of interest to various plant biologists and plant breeders. Male-sterile mutants serve as useful tools for investigations into the genetic, molecular, physiological, and developmental processes involved in stamen and pollen development. The sterility of the male reproductive organ is also considered a major mechanism by which gynodioecy is believed to have originated (Bawa 1980). For plant breeders, male-sterile plants are useful systems for interspecific hybridization and for performing backcrosses.Perhaps the most widely accepted use of male sterility is in the production of F1 hybrid seed in monoecious and hermaphrodite crops (Frankel and Galun 1977; Kaul 1988).