8. Open hull male sterile mutant in rice

Kazuyoshi TAKEDA

Institute for Agricultural Biology, Okayama University, Kurashiki, 710 Japan

A spontaneous mutant with open-hull male sterility was found in an experimental line (Fig. 1). The mutant was characterised also by lower seed fertility,


Table 1. Segregation of the 'open hull male sterile' mutant in
         F2 populations
_______________________________________________________________
                        Number of plants
Sample  ____________________________________       X2 (3: 1)
        Normal        Mutant        Total
_______________________________________________________________
1         88            28           116              0.05
2         96            25           121              1.22
3        112            20           132              6.83**
4         82            28           110              0.01
5         73            14            87              3.68
6         84            26           110              0.11
7         69            13            82              3.66
8         91            23           114              1.42
Total    695           177           872             10.28**
_______________________________________________________________
**Significant at the 1% level.
Heterogeneity: X2 = 6.70(df = 7),P=0.3-0.5.
smaller caryopsis, darker leaf color, and remarkable ratooning. The anthers of the mutant were white and small, without viable pollen. No seed was developed in the panicles when bagged before anthesis. Spikelet fertility of naturally open- pollinated panicles was 5-20%. All the plants derived from the seeds set on the mutant were phenotypically normal, suggesting that the seeds were produced by cross pollination with normal plants.

F2 segregation indicated that this mutant was controlled by a single recessive gene, although the observed number of mutants was somewhat smaller than expected (Table 1). As this mutant is distinguishable from other open-hull mutants (RGN 1, p. 40) by its male sterility, the new gene may be named oms (open-hull male sterile).