Introduction

Abstract

Flowering represents the end result of many gene-controlled physiological processes, biochemical sequences and morphological events. The principle functions of a flower are: microspore and megaspore formation, pollen release and reception, guided male and female gametophyte development, gametic union and seed formation. All these constitute time sequence-programmed gene-controlled functions. Breakdown of any one of these functions occurs due to mutation of the genes controlling them (Kaul and Murthy 1985). One such event causes male sex abolition and leads to the evolution of new sex types, the male steriles. Their natural development, subsequent establishment, genetic features and breeding utility comprise the text of this monograph.