Hybrid wheat breeding using photoperiod-sensitive cytoplasmic male sterility (PCMS) caused by <i>Aegilops crassa</i> cytoplasm

Photoperiod-sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under long-day (LD) photoperiods (≧15 h) has been proposed as a two-line system for producing hybrid varieties of common wheat (Triticum aestivum). PCMS lines are maintained by self-pollination under short-day (SD) conditions (＜15 h), while outcrossing PCMS plants to a T. aestivum pollinator line under LD conditions produces hybrid seeds. In this system, it is not necessary to have maintainer lines in order to sustain the PCMS lines. Several promising elite PCMS lines with a Japanese wheat cultivar ‘Fukuotome’ genetic background have been developed; these lines show high cross-pollination fertility and high male sterility under LD conditions, and high seed fertility under SD conditions. In addition, the European wheat cultivar ‘Fortunato’ was found to be suitable for use in the PCMS system. Through the use of the PCMS elite lines and the selected pollinator line, F1 seeds have been produced under LD conditions in Hokkaido, Japan, and the agronomic characters of F1 hybrids have been examined under SD conditions in Fukui, Japan. The results indicate the practicality of using this PCMS system for hybrid wheat production in Japan.