Improving parental lines to increase efficiency of hybrid rice breeding:some new approaches

摘要

Because of the potential of hybrid rice to increase rice production and productivity, many countries are currently working to exploit the benefits of this technology. The major problems in hybrid rice breeding are the limited number of parental lines with specific desirable traits, a lower frequency of maintainers and restorers among elite breeding lines, the narrow genetic base, a lack of resistance to biotic stresses, and poor grain quality of some parental lines. Therefore, improving parental lines must be an integral part of hybrid rice breeding to develop heterotic hybrids and improve breeding efficiency.The frequency of maintainers and restorers has been significantly increased after initiating specific maintainer and restorer breeding programs. Diverse parental lines with better grain quality and multiple resistance have been developed in China and at IRRI. Random mating of composite populations of maintainers and restorers developed at IRRI has helped to widen the genetic base of parental lines. Transferring restorer genes into tropical japonicas and incorporating wide compatibility genes into promising elite lines are considered essential to developing indica/japonica hybrids.Thermosensitive genic male sterile lines are being generated inndica, tropical japonica, and basmati genetic backgrounds. Anther culture and marker-aided selection can be deployed to expedite the parental line improvement program. This chapter discusses the limitations in current parental lines, progress made in improving them, and strategies envisaged to increase the efficiency of hybrid rice breeding.