Abstract
Aegilops crassa cytoplasm causes photoperiod-sensitive Introductron cytoplasmic male sterility (PCMS) to some Japanese common wheat (Triticum aestivum ) cultivars: the PCMS line with the Ae. crassa cytoplasm is almost completely male sterile under long-day conditions (≥l5 h light period), but highly male fertile under short-day conditions (≤14.5 h). Using the PCMS, a “two-line systerm” is applicable for hybrid wheat production. To examine the effects of Ae. crassa cytoplasm on the agronomic characters in the PCMS Iines and F1 hybrids, five PCMS Iines and 23 F1 hybrids with the Ae. crassa cytoplasm were compared their agronomic characters to the corresponding lines with the wheat cytoplasm under a short-day condition (natural condition at Kasai, Hyogo, Japan). In the PCMS Iines, the Ae. crassa cytoplasm delayed heading date and reduced spikelet number/ear. Shriveled kernels were found in the PCMS seeds, resulting in decreased volume weight and germination rate. Although the Ae. crassa cytoplasm reduced selfed and open-pollinated seed fertilities in the PCMS Iines, the averaged 69 % open-pollinated seed fertility indicates that the PCMS Iines can be maintained by self-pollination under the natural condition at Kasai. In the F1 hybrids, selfed and open-pollinated seed fertilities were also reduced by the effect of Ae. crassa cytoplasm. The reduced seed fertility resulted in decreased grain numberlear and grain weight/plant, but increased 1, 000-grain weight. No significant effect of the cytoplasm was detected on volume weight of the seeds produced by the F1 hybrids, suggesting no seriously deleterious effects of Ae. crassa cytoplasm on the grain quality. In spite of reduced seed fertility, the F1 hybrids with the Ae. crassa cytoplasm showed on the average 14 % heterosis for grain weight/plant over the mid-parent value of the female and male parents with the wheat cytoplasm. Correlation analysis revealed that grain weight/plant was more strongly related with the ear number/plant and grain numberlear than the 1, 000-grain weight in both F1 hybrids with the Ae. crassa and wheat cytoplasm.
