PHOTOPERIOD-SENSITIVE CYTOPLASMIC MALE-STERILITY IN WHEAT WITH AEGILOPS-CRASSA CYTOPLASM

Triticum aestivum cv. Norin 26 with Aegilops crassa, Ae. juvenalis or Ae. vavilovii cytoplasm (all D2 type) has been studied relative to its photoperiodic response of male sterility and fertility restoration patterns. Alloplasmic mic lines of 'Norin 26' with a D2 type cytoplasm showed almost complete male sterility under long-day conditions (greater-than-or-equal-to 15 h), but high male fertility under short-day conditions (less-than-or-equal-to 14.5 h). No significant influence of temperature on reduction in male fertility was observed. Thus, this type of male sterility is called 'photoperiod-sensitive cytoplasmic male sterility' (PCMS). The PCMS is expressed in the form of pistillody of stamens. Histological studies revealed that there were incomplete ovule-like structures instead of tapetal cells and pollen grains in the pistillate stamens. The floret differentiation stage of the plant is the stage that is sensitive to photoperiod. The PCMS can be used as a new means for hybrid wheat production, named 'two-line system'. The PCMS line is maintained and multiplied by self-fertilization under short-day conditions, and hybrid seed can be produced by crossing the PCMS line with a pollinator line under long-day conditions. In contrast to the system of hybrid wheat production using the T. timopheevi cytoplasm, the present system requires only PCMS and pollinator lines.