Cytological and Molecular Mechanisms Underlying Male Sterility in Hybrid Rice Production

Henry Doku and Nkatha Muriira

Hybridization is an important conventional breeding technique employed to produce crops with superior desirable traits compared to their original parents. Rice normally self-pollinates, therefore, male-sterile lines have been developed to produce female parents for commercial hybridization. The natural types of male sterility employed for hybrid rice production are cytoplasmic male sterility (CMS) and environmental genic male sterility (EGMS). To maximize the potential of the male sterility systems for hybrid rice production, an in-depth understanding of the molecular mechanisms underlying these phenomena is required to extend their utilization and further applications. The quest to determine the mechanisms that regulate male sterility has attracted enormous effort over the past few decades. The molecular basis of some male sterile lines has been determined, but many remain undescribed. This article reviews the state of research on rice male sterility (MS), including cytological studies, mapped genes, and underlying molecular mechanisms. Research gaps that require further investigation to facilitate progress in improving hybrid rice technology are discussed. With established evidence that genes whose mutations confer male sterility in rice plants are associated with pollen and/or anther development abnormalities, understanding the genetic interactions and molecular regulatory network among most of these rice MS-associated genes holds great promise to enhance hybrid seed production.

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