Chemicals that can sterilize the stamen, with little or no effect on the normal functioning of the pistil, can be used to produce female parents for hybrid rice production. The advantages are obvious, no special development of male sterile and restorer lines is required, and extensive varietal resources are available. Chemical emasculators such as male gametocide 1 (MG1) and male gametocide 2 (MG2) were developed in China and have been used in hybrid rice production. Two of the most popular hybrids, Gang-Hua 2 and Gang-Hua/Qing-Lan, were developed by chemical emasculation. Future emphasis will be placed on the development of more effective and nontoxic chemicals. Preliminary techniques for hybrid seed production by chemical emasculation began in China in the 1970s. Present methods for producing high yields of high-quality, low-cost hybrid rice seed are discussed.
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