F₁ Seed Production Efficiency by Using Photoperiod-sensitive Cytoplasmic Male Sterility and Performance of F₁ Hybrid Lines in Wheat

Abstract

Photoperiod-sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm to common wheat (Triticum aestivum) under long-day conditions (≥15 h light period) has been reported as a new means of producing hybrid wheat, that is a “two-line system”. The PCMS Iine is Inaintained by self-pollination under short-day conditions (≤14.5 h light period), and F₁ seeds can beproduced by outcrossing of the PCMS Iine with a pollinator under long-day conditions. A cross pollination study for producing F₁ seeds was carried out using three PCMS Iines and three restorer lines under a long-day condition at Tanno, Hokkaido, Japan. Seed setting rate was 14-33%, and 19-55 g/m² F₁ seeds with 47-88% hybrid purity were obtained. Variation in seed setting rate attributable to male parents was highly significant. High seed setting rate was achieved by using a pollinator taller than the PCMS Iine. Shriveled and preharvest sprouting kernels were found in the out-crossed F₁ seeds, resulting in lower volume weight and germination rate than the selfed seeds of original cultivars of the PCMS Iines. A field test of evaluating four F₁ hybrids with high hybrid purity (>65 %) was conducted under a short-day condition at Kasai, Hyogo, Japan. All F₁ hybrids exhibited higher grain yield than their respective better-parent because of more spikelet number/ear and higher 1000 grain weight. The top F₁ hybrid yielded 40% more than the mid-parent and 37% more than the better-parent, suggesting a possibility of the practical use of this system for hybrid wheat breeding. F₁ hybrids tended to show higher volume weight than their parental cultivars. This indicates that grain quality of the F₁ hybrids with the Ae. crassa cytoplasm is not inferior to those of parental cultivars with the wheat cytoplasm.