(go to KOMUGI Home) (go to WIS List) (go to NO.72 Contents)

---

Wheat Information Service
Number 72: 91-94 (1991)


A new system for hybrid wheat production using Aegilops crassa cytoplasm

K. Murai¹, H. Hirohara¹ and K. Tsunewaki²

1 Takarazuka Research Center, Sumitomo Chemical Co., Ltd. Takarazuka, Hyogo 665, Japan

2 Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606, Japan


Sasakuma and Ohtsuka (1979) observed complete male sterility in the alloplasmic line of Triticum aestivum cv. Norin 26 having Aegilops crassa cytoplasm (D² type cytoplasm by Tsunewaki 1980) in Hokkaido, a northern island of Japan. We showed that the male sterility was induced by long-day treatments exposed during the floral differentiation stage of the plants (Murai et al 1988). In this report, we propose a new system for hybrid wheat production using the D² type cytoplasm.


Materials and Methods

Alloplasmic lines, Ae. crassa /11* Norin 26 ((C)-N26) and Ae. crassa /11* Chinese Spring ((C)-CS) were used. Euplasmic and alloplasmic lines of N26 and CS were planted under various photoperiodic conditions in phytotrons as well as in the fields of the Kasai Experimental Farm of Sumitomo Chemical Co., Hyogo, and the Tanno Agricultural Cooperative, Hokkaido. Selfed seed fertility was estimated by the seed setting rate of first and second florets of all spikelets. A field trial for hybrid seed production was performed at Tanno, and yield and purity of hybrid seeds were estimated with the materials grown in the field (see Table 3).


Results and Discussion

The alloplasmic line of N26 shows almost completely male sterility under the long-day conditions of more than 15.0 hr light period, whereas N26 with normal cytoplasm is fertile under all photoperiodic conditions tested. Similarly, both the euplasmic and alloplasmic lines of CS exhibit high male fertility under the all conditions (Table 1). These results indicate that male sterility is induced by and interaction between the N26 nucleus and Ae. crassa cytoplasm under long-day conditions of more than 15.0 hr light period, and that the CS nucleus has some genetic factors which prevent the reduction of male fertility under long-day conditions. This male sterility will be called "photoperiod-sensitive cytoplasmic male sterility (PCMS)" to distinguish it from other types of cytoplasmic male sterility. The PCMS is caused by pistillody (Fig. 1).

The PCMS enables us to propose a new system for hybrid wheat production as shown in Fig. 2. Under the long-day conditions of more than 15.0 hr light period (condition A), hybrid seeds can be produced from the outcrossing of a PCMS line with a cultivar used as the pollinator. The PCMS line can be easily maintained by self-pollination, under photoperiodic condition of less than 15.0 hr light period (condition B). Hybrid wheat is grown in areas under the condition B. In contrast to the system of hybrid wheat production using T. timopheevi cytoplasm, the present system requires only PCMS and pollinator lines so that it is called a "two-line system".

As for in Japan, the condition A is found in Hokkaido and the condition B in southern part of Honshu, Kyushu and Shikoku islands. In fact, the alloplasmic line of N26 can be maintained by self-pollination at the Kasai Farm in Honshu and is used as PCMS line in the field at Tanno, Hokkaido, where male sterility is expressed (Table 2). In the field trial at Tanno, we could get 93.5 g/m² hybrid seeds of 75.2% purity (Table 3).


References

Sasakuma T and Ohtsuka I (1979) Cytoplasmic effects of Aegilops species having D genome in wheat. I. Cytoplasmic differentiation among five species regarding pistillody induction. Seiken Ziho 27-28: 59-65.

Tsunewaki K (1980) Genetic diversity of the cytoplasm in Triticum and Aegilops. Japan Society for the Promotion of Science, Tokyo.

Murai K, Tsuji S, Hirohara H, Ohtsuka I and Tsunewaki K (1988) Breeding of hybrid wheat using photoperiod-sensitive cytoplasmic male sterility (PCMS). I. Breeding system of hybrid wheat. Japan J Breeding 38 (Suppl 2): 284-285.

(go to KOMUGI Home) (go to WIS List) (go to NO.72 Contents)