AN EMS-INDUCED WHEAT MUTANT RESTORING FERTILITY AGAINST PHOTOPERIOD-SENSITIVE CYTOPLASMIC MALE-STERILITY

Triticum aestivum cv. 'Norin 26' with Aegilops crassa cytoplasm shows photoperiod-sensitive cytoplasmic male sterility (PCMS). This alloplas mic line is almost completely male-sterile under long-day conditions ( greater than or equal to 15 h), but highly male-fertile under short-da y conditions (greater than or equal to 14.5 h). To obtain male-fertile mutants against PCMS, seeds of the alloplasmic line were treated with ethyl methane sulfonate (EMS). The M(3) generation was evaluated for PCMS expression, and one fertility-restoring (FR-mutant) line showing high male fertility under the long-day conditions was selected. Recipr ocal F-1 hybrids between the FR-mutant and the alloplasmic 'Norin 26' showed male sterility under the long-day conditions, and continuous se gregation with respect to the degree of fertility restoration occurred in their F-2 generations. These results indicate that multiple recess ive mutations with minor effects, induced in the nuclear genome, are i nvolved in the fertility restoration. In fact, no restriction-fragment -length polymorphisms of mitochondrial DNA between the FR-mutant and t he alloplasmic 'Norin 26' are found.