Male Sterility Systems for Hybrid Rice Breeding

Abstract

Plants that fail to produce functional pollen grains are male sterile. Rice, being a self-pollinating crop, must involve use of an effective male sterility system to develop and produce F₁ hybrid varieties. Major male sterility systems used for hybrid rice breeding in China and elsewhere are cytoplasmic-genetic and chemically induced male sterility. Recently, photoperiod-sensitive and thermo- sensitive genetic male sterility systems are also being tested for their usability. Out of a total area of 15 million ha grown under hybrid rices in China, only about 10 000 ha are covered with hybrids developed by using chemically induced male sterility; the rest of the area is grown with hybrids involving cytoplasmic genetic male sterility and a fertility restoration system. Outside China, hybrid rice breeding programs are also deploying mainly the cytoplasmic genetic male sterility system. Use of photosensitive and thermo-sensitive genetic male sterility is still in an experimental stage. During 1990, some rice hybrids based on the photoperiod-sensitive genetic male sterility system were tested under farmers’ field conditions in China (L. P. Yuan, pers. comm.). In this chapter, male sterility systems used in hybrid rice breeding are described and their relative significance discussed.