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.